HK1218321B - Directional drilling communication protocols, apparatus and methods - Google Patents

Abstract

A transmitter is carried proximate to an inground tool for sensing a plurality of operational parameters relating to the inground tool. The transmitter customizes a data signal to characterize one or more of the operational parameters for transmission from the inground tool based on the operational status of the inground tool. A receiver receives the data signal and recovers the operational parameters. Advanced data protocols are described. Pitch averaging and enhancement of dynamic pitch range for accelerometer readings are described based on monitoring mechanical shock and vibration of the inground tool.

Description

Directional drilling communication protocol, apparatus and method

Cross Reference to Related Applications

This application claims priority from U.S. provisional patent application No.61/785,410, filed on 3/14/2013, the contents of which are incorporated herein by reference in their entirety. This application also claims priority from U.S. application Ser. No.14/208.470 entitled "DIRECTIONAL DRILLING COMMUNICATION PROTOCOLS, APPATUS AND METHODS", filed 3/13/2014, the contents of which are incorporated herein by reference in their entirety.

Background

The present invention relates generally to the field of directional drilling, and more particularly to an advanced directional drilling communication protocol, apparatus and method.

A technique often referred to as Horizontal Directional Drilling (HDD) may be used for the purpose of installing utilities without the need to dig trenches. One typical utility installation involves the use of a drilling rig having a drill string that supports a drilling tool at the lower or distal end of the drill string. The drilling rig propels the drilling tool through the ground by applying a thrust force to the drill string. The drill tool is steered during extension of the drill string to form a pilot bore. When the pilot hole is completed, the distal end of the drill string is connected to a callback device, which in turn is connected to the front end of the utility. The setback device and utilities are pulled through the pilot hole by retraction of the drill string to complete the installation. In some cases, the callback device includes a back-reaming tool for dilating the diameter of the pilot hole at the front of the utility, so that the installed utility has a larger diameter than the original diameter of the pilot hole.

Steering the drill tool may be accomplished in a well-known manner by orienting the plane of symmetry of the drill tool in response to forward movement so as to effect a desired directional bias at the surface. To control such steering, it is desirable that the direction of the drill tool can be monitored from sensor readings obtained based on sensors forming part of an electronics package supported by the drill tool. The sensor readings, for example, may be modulated on a positioning signal emitted by the electronics package for reception on the ground by a portable locator or other suitable ground device. In some systems, the electronics package may couple a carrier signal modulated by the sensor readings to the drill string, and then transmit the signal to the drill rig by using the drill string as an electrical conductor. Regardless of the manner in which the sensor data is transmitted, there is a defined transmission range for a quantitative transmission power within which the sensor data can be recovered with sufficient accuracy. The transmission range may be further limited by factors such as electromagnetic interference present in the operating area. One prior art technique for attempting to increase the transmission range is to simply increase the transmission power. However, applicants have appreciated that this approach is of limited value, particularly when the underlying electronics package is battery powered, as will be discussed further below. Another approach is to reduce the data or baud rate at which data is modulated onto the positioning signal. Unfortunately, this approach can result in a reduction in data throughput.

The foregoing examples of the prior art and limitations associated therewith are intended to be illustrative and not exclusive. Other limitations of the prior art will become apparent to those of skill in the art upon a reading of the specification and a study of the drawings.

Disclosure of Invention

The following embodiments and aspects thereof are described and illustrated in conjunction with systems, tools, and methods which are meant to be exemplary and illustrative, not limiting in scope. In various embodiments, one or more of the above-described problems have been reduced or eliminated, while other embodiments are directed to other improvements.

In one aspect of the present disclosure, an apparatus and associated method are used in conjunction with a system for performing subterranean operations in which a drill string extends from a drill rig to a subterranean tool such that extension and retraction of the drill string generally produces corresponding movement of the subterranean tool during subterranean operations. The transmitter is configured to be disposed proximate to the inground tool for sensing a plurality of operating parameters associated with the inground tool and for customizing the data signal to characterize one or more of the operating parameters for transmission from the inground tool based upon the operational status of the inground tool. A receiver is positionable at a location on the ground for receiving the data signal and recovering the operating parameters.

In another aspect of the present disclosure, a transmitter and associated method are described for use in conjunction with a receiver as part of a system for performing subterranean operations in which a drill string extends from a drill rig to a subterranean tool supporting the transmitter such that extension and retraction of the drill string generally produces corresponding movement of the subterranean tool during subterranean operations. The transmitter includes at least one sensor for sensing one or more operating parameters related to the operating condition of the inground tool and a processor configured for customizing the data signals transmitted from the transmitter based on the operating condition of the inground tool.

In another aspect of the present disclosure, a receiver and associated method are described for use in conjunction with a transmitter that is part of a system for performing subterranean operations in which a drill string extends from a drill rig to a subterranean tool that supports the transmitter such that extension and retraction of the drill string generally produces corresponding movement of the subterranean tool during subterranean operations. The receiver is configured to receive a data signal transmitted by the transmitter that characterizes one or more operating parameters related to an operating condition of the inground tool such that the data signal is customized based on the operating condition. The processor is configured to decode the customized data signal to recover one or more operating parameters.

In another aspect of the present disclosure, transmitters and associated methods are described for use in conjunction with a system for performing subterranean operations in which a drill string extends from a drill rig to a subterranean tool such that extension and/or rotation of the drill string moves the subterranean tool along a subterranean path while being subjected to mechanical shock and vibration. An accelerometer, which is part of the transmitter, is used to sense the pitch orientation in each of the high and low resolution ranges when the inground tool is subjected to mechanical shock or vibration to produce a series of pitch readings. The processor is configured to monitor a series of pitch readings and in response thereto to select one of a high resolution range and a low resolution range to characterize the pitch orientation, and to average the series of pitch readings for the selected one of the high resolution range and the low resolution range to produce an average pitch reading transmitted from the transmitter.

In one continuing aspect of the present disclosure, transmitters and associated methods are described for use in connection with performing an inground operating system in which a drill string extends from a drill rig to an inground tool such that extension and/or rotation of the drill string moves the inground tool along an inground path while being subjected to mechanical shock and vibration. An accelerometer forms part of the transmitter for sensing the pitch orientation of the inground tool to produce a series of pitch readings. The processor is configured to average a series of pitch readings to produce an average pitch reading transmitted from the transmitter.

In yet another aspect of the present disclosure, it is recognized that advanced data protocols may be selectively employed, for example, to increase the update rate of one or more parameters used in connection with monitoring the inground tool. These advanced data protocols can greatly reduce the amount of data required to effectively characterize a given parameter, e.g., based on the resolution at which the parameter is changed, such that fewer data bits are required. By way of non-limiting example, a transmitter and associated method are described for use in conjunction with a receiver as part of a system for performing an inground operation in which a drill string extends from a drill rig to an inground tool that supports the transmitter such that extension and retraction of the drill string generally produces corresponding movement of the inground tool during the inground operation. At least one transmitter forms a portion of the transmitter for sensing one or more operating parameters associated with the inground tool. The processor is configured to transmit data relating to one or more operating parameters in a standard mode and an optional mode, such that the optional mode uses fewer bits to characterize at least one particular operating parameter than the standard mode, the optional mode representing the particular parameter at a lower resolution than the standard mode.

In another aspect of the disclosure, a transmitter and associated method are described for use in conjunction with a receiver as part of a system for performing an inground operation in which a drill string extends from a drill rig to an inground tool that supports the transmitter such that extension and retraction of the drill string generally produces corresponding movement of the inground tool during the inground operation. At least one sensor forms part of the transmitter for sensing one or more operating parameters associated with the inground tool. The processor is configured to transmit the digital signal from the transmitter using a plurality of data packet communication protocols including a particular protocol that characterizes one or more operating parameters with a fixed data frame and repeatedly transmits the fixed data frame in response to detecting a quiescent state of the transmitter.

Drawings

Exemplary embodiments are illustrated in referenced figures of the drawings. The embodiments disclosed herein are intended to be illustrative and not restrictive.

FIG. 1 is a schematic view of an embodiment of a system for performing subterranean operations using advanced communication protocols between a subterranean transmitter and a portable device according to the present disclosure.

FIG. 2 is a block diagram illustrating an embodiment of an electronic package that may be carried by an inground tool and implemented in accordance with the present disclosure.

FIG. 3 is a flow chart illustrating an embodiment of a method for monitoring pitch of an inground tool and applying a non-linear pitch range profile.

FIG. 4 is a flow diagram illustrating an embodiment of a method for customizing the packet structure of a data packet transmitted from an inground tool based on the operating condition or state of the inground tool.

FIG. 5 is a flow diagram illustrating an embodiment of a method for dynamically invoking fixed-length packetization for global averaging in response to an operational state of an inground tool.

FIG. 6 is a flow diagram illustrating an embodiment of a method of dynamically customizing g-force sensing to increase dynamic range based on operating conditions encountered by the inground tool.

Detailed Description

The following description is presented to enable one of ordinary skill in the art to make and use the invention and is provided in the context of a patent application and a patent requirement. Various modifications to the described embodiments will be readily apparent to those skilled in the art and the generic principles taught herein may be applied to other embodiments. Thus, the present invention is not intended to be limited to the embodiments shown, but is to be accorded the widest scope consistent with the principles and features disclosed herein, including modifications and equivalents. It should be noted that the drawings are not to scale but are schematic in nature to best illustrate features of interest in one way. Descriptive terms may be employed for enhancing the reader's understanding with respect to the different perspectives provided in the figures, without limiting the scope of the invention in any way.

Referring now to the drawings, in which like items are designated by like reference numerals throughout the several views, attention is now directed to FIG. 1, which illustrates one embodiment of a system for performing subterranean operations, which is generally designated by reference numeral 10. The system includes a portable device 20 shown held by an operator on a ground surface 22, which is also shown in a further enlarged inset view. It should be noted that the inner member cables in the device 20 are not shown to maintain clarity of view, but should be understood to exist and can be readily implemented by one of ordinary skill in the art in view of the entire disclosure. The apparatus 20 includes a three-axis antenna cluster 26 for measuring three orthogonally arranged components of magnetic flux, denoted b_x,b_yAnd b_z. One useful antenna group contemplated for use herein is disclosed by U.S. patent No.6,005,532, which is commonly owned with the present application and incorporated herein by reference. The antenna cluster 26 is electrically connected to the receiver portion 32. The tilt sensor arrangement 34 is provided to measure the gravitational angle from which the flux component in a horizontal coordinate system can be determined.

The device 20 further includes a graphical display 36, a telemetry device 38 having an antenna 40 and a processing portion 42 suitably interconnected with the various components. The telemetry device may transmit a telemetry signal 44 for reception at the drilling rig. The processing section may include a Digital Signal Processor (DSP) configured to execute various programs required in operation. It should be understood that the graphical display 36 may be a touch screen to assist the operator in selecting the different buttons defined on the screen and/or may be conveniently scrolled between the different buttons defined on the screen that are provided for operator selection. Such a touch screen may be used alone or in combination with an input device 48 such as a key. The latter can be used without a touch screen. Also, many variations of input devices may be employed and scroll wheels and other suitable known forms of selection devices may be used. The processing portion includes such components as one or more processors, any suitable type of memory, and analog-to-digital converters. As is well known in the art, the latter can detect frequencies at least twice the highest frequency of interest. Other components may be added as desired, for example, a magnetometer 50 is used to aid in positioning relative to the direction of drilling, while an ultrasonic transducer is used to measure the height of the device above the surface.

Still referring to fig. 1, the system 10 further includes a drill rig 80 having a carriage 82 mounted for movement along the length of a pair of oppositely disposed rails 83. An inground tool 90 is connected to an opposite end of a drill string 92. By way of non-limiting example, an inground tool is shown as a drill and is used as the framework for this description, but it should be understood that any suitable inground device may be used, such as a reaming tool or a mapping tool for use in performing a pullback operation. Generally, the drill string 92 is made up of a plurality of removably attachable drill pipe sections such that the drill rig can advance the drill string into the ground with movement in the direction of arrow 94 and can retract the drill string in response to movement in the reverse direction. The drill pipe sections define through passages for conveying drilling mud or liquid that is launched by the drilling tool under pressure to aid in cutting through the surface and cooling the drill bit. Typically, drilling mud is also used to suspend cuttings and bring the cuttings to the surface along the outer length of the drill string. Steering may be accomplished by orienting the asymmetric face 96 of the directional drilling tool to deflect in the desired direction in the ground in response to a forward, propulsive motion, which may be referred to as a "propulsion mode". The rotation or spinning of the drilling machine about the drill string will typically result in forward or straight advancement of the drilling tool, which may be referred to as a "spin" or "go" mode.

The drilling operation is controlled by an operator (not shown) at a console 100 (preferably seen in an enlarged inset view), the console 100 including a telemetry transceiver 102 connected to a telemetry antenna 104, a display screen 106, an input device such as a keyboard 110, a processing apparatus 112, which may include a suitable interface, memory, and one or more processors. A plurality of control rods 114, for example, control the movement of the carriage 82. Telemetry transceiver 104 may transmit telemetry signals 116 to facilitate two-way communication with portable device 20. In an embodiment, the screen 106 may be a touch screen, and thus the keyboard 110 is optional.

The apparatus 20 is configured to receive an electromagnetic locating signal 120 transmitted from a drilling tool or other subterranean tool. The locating signal may be a dipole signal. In this case, the portable device is consistent with any of the portable devices described below, for example, U.S. Pat. Nos. 6,496,008, 6,737,867, 6,727,704, and U.S. published patent application No.2011-0001633, any of which are incorporated herein by reference. With these patents in mind, it should be understood that the portable device may operate in a locate mode, as shown in FIG. 1, or in a home mode, where the portable device is placed on the ground, as shown in U.S. Pat. No.6,727,704. While the present disclosure shows a dipole localization field emanating from the drill tool and rotating about the field's axis of symmetry, the present disclosure is not so limited.

The positioning signal 120 may be modulated by drill-generated information including, but not limited to, position orientation parameters based on pitch and roll orientation sensor readings, temperature values, pressure values, battery status, tension readings in the context of a pullback operation, and the like. The apparatus 20 receives the signal 120 using the antenna array 26 and processes the received signal to recover the data. It should be noted that as an alternative to modulating the positioning signal, the object information may be conducted from the drill string to the drilling rig using, for example, the electrical conductance of the conduit installation. In another embodiment, bidirectional data transfer may be accomplished by using the drill string itself as a conductor. Advanced embodiments of such a system are described in commonly owned U.S. application serial No. 13/733,097, which is disclosed in U.S. published application No.2013/0176139, which is hereby incorporated by reference in its entirety. In either case, all of the information is available at the console 100 of the drilling rig.

Fig. 2 is a block diagram illustrating an embodiment of an electronic package, generally designated by the reference numeral 200, that may be supported by the drilling tool 90. The electronics package may include an underground digital signal processor 210. The sensor portion 214 may be electrically coupled to the digital signal processor 210 via an analog-to-digital converter (ADC) 216. Any suitable combination of sensors may be provided for a given application and may be selected, for example, from accelerometer 220, magnetometer 222, temperature sensor 224, and pressure sensor 226, which pressure sensor 226 may detect drilling fluid pressure in an annular region before drilling fluid is launched from the drill string and/or near a downhole portion of the drill string. In embodiments where communication with the drilling rig is implemented using the drill string as a conductor, the isolator 230 forms an electrically isolated connection in the drill string and is diagrammatically shown for separating an uphole portion 234 of the drill string from a downhole portion 238 of the drill string in one or both of a transmit mode, in which data is coupled to the drill string, and a receive mode, in which data is recovered from the drill string. In many implementations, electrical isolation may be provided as part of the inground tool. As shown, the electrical portions may be connected by a first lead 250a and a second lead 250b, generally indicated by reference numeral 205, across the electrically insulating/isolating space formed by the isolator. For the transmit mode, an antenna driver section 330 is used which makes an electrical connection between the subsurface digital signal processor 210 and the lead 250 to directly drive the drill string. In general, the data coupled to the drill string may be modulated at any frequency other than that used to drive the dipole antenna 340 capable of transmitting the signal 120 (FIG. 1) described above to avoid interference. When the antenna driver 330 is off, the on/off Switch (SW)350 may selectively connect the leads 250 to a Band Pass Filter (BPF)352 having a center frequency corresponding to the center frequency of the data signal received from the drill string. The BPF 352 in turn is connected to an analog-to-digital converter (ADC)354, which itself is connected to the digital signal processing section 210. In an embodiment, a DC blocking anti-aliasing filter is used instead of a band pass filter. The recovery of the modulated data in the digital signal processing section can be readily accomplished by one of ordinary skill in the art in view of the particular form of modulation employed and in view of the present disclosure as a whole.

Still referring to FIG. 2, dipole antenna 340 may be used in conjunction in one or both of a transmit mode, in which signals 120 are transmitted around the earth's surface, and a receive mode, in which electromagnetic signals are received, the electromagnetic signals being transmitted from an inground tool such as a tension monitor. For the transmit mode, an antenna driver portion 360 is used that makes an electrical connection between the subsurface digital signal processor 210 and the dipole antenna 340 to drive the antenna. Again, the frequency of the signal 120 is typically sufficiently different from the drill string signal frequency to avoid interference with each other. When the antenna driver 360 is turned off, the on/off Switch (SW)370 can selectively connect the dipole antenna 340 to a Band Pass Filter (BPF)372 having a center frequency corresponding to a center frequency of the data signal received from the dipole antenna. In an embodiment, a DC blocking anti-aliasing filter is used instead of a band pass filter. The BPF 372 is in turn connected to an analog-to-digital converter (ADC)374, which is itself connected to the digital signal processing portion 210. The transceiver electronics of the digital signal processing section may be readily constructed in many suitable embodiments by one of ordinary skill in the art, taking into account the particular form or forms of modulation applied and taking into account the invention as a whole. The design shown in fig. 2 may be modified in any suitable manner based on the teachings already disclosed herein.

Referring again to fig. 1, the range of the positioning signal 120 received by the portable device 20 is inversely proportional to the cube of the distance. While increasing transmit power from the inground tool increases range, it should be understood that doubling transmit power only results in a 15% increase in range. Of course, when the transmitter supported by the inground tool is powered by a battery, battery life can be severely reduced in response to such power increases. Moreover, the reception range is greatly affected by local interference. Power line noise harmonics of (n × 50) Hz and (n × 60) Hz represent an important source of noise. In the past, the carrier frequency used for the positioning signal 120 was carefully selected to avoid power line harmonics. In some cases, avoiding power line harmonics requires narrowing the bandwidth of the data modulated on positioning signal 120. Applicants have appreciated that narrowing the data bandwidth results in lower data throughput. Relatively low data throughput values can be problematic in terms of achieving sufficiently fast data updates at the portable device. For example, relatively slow rolling orientation updates may cause this to be a time-consuming process when an operator attempts to establish a desired rolling orientation of the inground tool for steering purposes. From the foregoing, it is now apparent that there is a benefit in avoiding interference from noise and data throughput. To date, applicants have not been able to submit an effective solution in view of these conflicting interests. As will be seen, applicants have discovered data protocols that are tailored to more efficiently utilize the available data bandwidth in accordance with subterranean operations. It should be understood that these protocols are applicable to transmission by electromagnetic positioning signals or by using the drill string as a conductor. While certain concepts are described in terms of electromagnetic signals, these concepts are equally applicable to transmission on a drill string.

For the purposes of data transmission according to the present disclosure, data may be encoded on a carrier wave in any suitable manner, e.g., phase encoding, amplitude modulation, frequency modulation, or any suitable combination thereof. Certain modulation schemes, such as manchester encoding, are beneficial in maintaining signal energy at carrier frequencies that increase the range of localization. On the other hand, another modulation scheme, such as Quadrature Phase Shift Keying (QPSK), provides a relatively high data throughput for a given bandwidth.

In general, data may be transmitted in digital form on location signal 120 in a data packet structure. Data may be transmitted in data packets that are specific to a particular type of data. For example, different packet structures may be used to transmit roll data, pitch data, battery status, temperature, pressure, and the like. The shorter the data packet, the less susceptible it is to noise damage when received from the portable device 20. Since the data packets are transmitted to the portable device in a streaming manner, the portable device needs to be able to discern the beginning of a new data packet. Embodiments of the data packet disclosed herein may utilize synchronization bits to achieve this. In view of these basic principles, a number of unique packet structures will be described immediately below.

Table 1 illustrates an embodiment of a rolling packet based on the present disclosure in the case of manchester encoding, although the latter is not required. Consider by way of example below that a conventional rolling packet may encode 24 rolling positions (i.e., 15 degree increments) by using additional synchronization bits that do not contribute to the encoding. Applicants have appreciated that the synchronization bits may be used to contribute to the encoding. At the same time, the number of code scroll positions can be reduced to reduce the size of the scrolling data packet. For example, the applicant found that 8 coded roll positions are sufficient to identify the roll orientation of the drill tool, so that only 3 data bits are necessary. Table 1 illustrates the scrolling packet structure for 8 scrolling positions. Each L (low) and H (high) value represents half of the bit time in a manner consistent with manchester encoding. Sync bit 1 and sync bit 2 represent bit 1 of the three data bits. In this embodiment, each synchronization bit comprises a half bit time. As seen in table 1, the sync bits 1 and 2 contain allowed sync interval values that include one of a 3 low bit time followed by a 3 high bit time (scrolling 1-4) or a 3 high bit time followed by a 3 low bit time (scrolling 5-8). Thus, the synchronization bit 1 and the synchronization bit 2 in combination may represent data bit 1 and only two additional data bits 1 and 2 are needed to together form 3 data bits for the purpose of encoding the three bit values. Thus, any embodiment of a packet may utilize the synchronization bit as the Most Significant Bit (MSB) in this manner. For example, temperature may be encoded normally, high and very high, such that a synchronization bit and only one data bit are required to encode a temperature data packet. It should be understood that packet transmission may be prioritized. For example, under normal temperature conditions, temperature packets may be sent at a fixed interval, e.g., 15 seconds. But temperature packets may be immediately transmitted when the rate of temperature change exceeds a certain threshold. By way of non-limiting example, such a temperature threshold may rise above 10 ℃ in 2 seconds. For example, a battery status packet may be encoded with 3 data bits in addition to the most significant bits represented by sync bits 1 and 2.

TABLE 1

Scrolling data packets

While the rolling packets are often targeted for the fastest update, the pitch packets are also transmitted quite frequently. As a non-limiting example, one pitch packet is transmitted every six roll packets. Conventionally, pitch packets are lengthy for the purpose of defining a high resolution pitch reading. For example, the conventional pitch data packet has a resolution of 0.05 ° or 0.1% regardless of the operating state of the drill. The applicant has appreciated that shock and vibration can severely limit the accuracy of pitch readings when the downhole tool is rotating or simply moving, which are produced by accelerometers in an electronically packaged sensor array carried by the drilling tool. This effect is even further exacerbated as the drilling tool advances through the rocky soil. Based on this knowledge, the resolution of the pitch data packets can be dynamically customized as the tool rotates and/or advances. One embodiment of the dynamic pitch packet resolution range is illustrated by table 2.

TABLE 2

Dynamic pitch resolution

Range of pitch	Number of data bits	Pitch resolution
			+/-16°	5	1°
17 DEG to 45 DEG +/-	6	1.5°

As seen in Table 2, the pitch reading includes 5 data bits to define a pitch resolution of 1 in the pitch range +/-16 as the underground tool moves. If a sync bit is used to represent the (+/-) sign of the pitch, only four data bits are required. Six data bits may be used to define a pitch resolution of 1.5 deg., from +17 deg. to +45 deg. and from-17 deg. to-45 deg., on either side of the +/-16 deg. range. If a sync bit is used to represent the (+/-) sign of the pitch, only 5 data bits are required.

It should be understood that the pitch reading may be limited to (+/-)45 ° at least from a practical standpoint. High accuracy pitch readings are satisfactory in certain circumstances, for example, gravity sewer installation. While providing such high resolution pitch accuracy is not practical when the tool is advancing and/or rotating, applicants have realized that it is practical to transmit high resolution pitch data packets in response to a stationary probed tool. Of course, such detection can be readily performed using accelerometers as part of a sensor array that is electronically packaged in a drill tool. At the same time, applicants have further recognized that the pitch data packet can be customized to utilize the data bits in an efficient manner when the drill string or other subterranean device is stationary. By way of non-limiting example, the pitch resolution may be compressed within a range of +/-11 deg. to provide high pitch resolution within this range, while providing a more liberal resolution outside of the range (i.e., when the pitch angle exceeds 11 deg.). In this regard, most gravity sewer line installations are limited to a level of +/-5%, which is approximately equivalent to +/-2.86 °. This static pitch resolution embodiment illustrated by table 3 includes the number of values in four different pitch ranges for a particular pitch resolution. A total of 509 values are required so a pitch packet with 9 data bits can be used to cover all four depicted pitch ranges. Also, if synchronization bits are used for the flag, only 8 data bits are needed.

TABLE 3

Static/dynamic pitch resolution

Representing pitch range in degrees

Number of values within range

Pitch resolution

+/-11	441	0.05°
			+12 to +20, -12 to-20	36	0.5°
+21 to +27, -21 to-27	14	1°
			+28 to +44, -28 to-44	18	2°

It should be understood that the static pitch resolution ranges in table 3 are provided by way of example and are not intended to limit the scope of the present invention, but rather illustrate an increased pitch resolution range in a non-linear manner for limiting the number of data bits required in a pitch packet. With the teachings already disclosed herein, the packet size can be significantly reduced, for example, to about 1/2 (i.e., factor 2), which will significantly increase the update rate in order to monitor the inground tool while providing adequate noise immunity with a narrow data bandwidth.

Fig. 3 is a flow chart illustrating one embodiment of a method, indicated generally by the reference numeral 400, for monitoring pitch and applying a non-linear pitch range profile, e.g., according to any of tables 2 and 3. The method begins at 404 and proceeds to 408, where the non-linear pitch resolution range of interest is invoked 408 and an initial range is set as a starting point. At 412, the current pitch value is measured as an input to step 416. The latter determines whether the current pitch is within the currently specified pitch range. If so, step 420 transmits the current pitch value at the resolution of the currently specified pitch range. The next pitch value is then obtained at 424. If step 416 detects that the current pitch reading is not within the currently specified pitch range, operation proceeds to 428, which sets the appropriate pitch range in accordance with the current pitch reading. Operation then returns to step 416.

Focusing attention on FIG. 4, FIG. 4 is a flow chart illustrating one embodiment of a method, indicated generally by the reference numeral 500, for altering a data packet structure based on the operating conditions of an inground tool. The method proceeds to 508 beginning at 504, where the packet structure used in this process is initialized 508. In one embodiment, for example, initialization may be based on the pitch orientation of the transmitter at startup. In another embodiment, initialization may be based on interference in the operating area, and thus an advanced packet protocol with higher noise/interference immunity as described herein may be used. For example, the local disturbance may be detected in any suitable manner, including in accordance with the methods of the aforementioned incorporated us 2011-0001633 application and/or the methods described in co-owned us published application No.2013/0176139, which is incorporated herein by reference. For example, the 2013/0176139 application teaches that sufficient degradation of the positioning signal can be detected based on an inability to decode roll orientation (roll orientation) information, pitch orientation (pitch orientation) information, and/or other state information. Further, a Bit Error Rate (BER) of the positioning signal may be monitored in relation to an acceptable threshold. At 512, the operational status of the inground tool can be determined by, for example, monitoring the accelerometer output for a brief period of time. If the inground tool is static, no brief acceleration is detected. If it is detected that the inground tool is stationary, operation proceeds to 516 where a static pitch packet structure or resolution is applied to the pitch packets to be transmitted, e.g., according to Table 3. The pitch data packet is then transmitted at 520. If, on the other hand, step 512 determines that the inground tool is not stationary, operation proceeds to 524 where a dynamic pitch packet structure and resolution are applied, for example, in accordance with Table 2.

In another embodiment, the signals from the various orientation sensors (accelerometers) should be stable and invariant when the underground tool is detected as stationary. Under these conditions, the electronic package may be converted into fixed-length data packets or data frames that include any desired set of data, such as roll orientation, pitch orientation, battery status, and temperature. The fixed length data frames may be repeatedly transmitted during the static state of the drill tool to allow the application of global averaging to the overall effect of increasing signal strength by increasing successive data frames while nulling out the sum of random noise. In this regard, if n is the number of samples and the noise is random, the signal-to-noise ratio increases by the square root of n. In other words, the greater the number of data frames added, the greater the contribution of the signal-to-noise ratio. The result is that it is enhanced with the stability of the clock in the electronic package 200 and the device 20. Apparatus 20 may employ a phase-locked loop to further enhance stability by locating the phase lock of the signal carrier. By way of non-limiting example, a fixed data frame may be represented by SSSRRRRPPPPPPPPPPPPPBBTT, where S represents a sync bit, R represents a roll data bit, P represents a pitch data bit, B represents a battery status data bit, and T represents a temperature status bit. A data buffer in the device 20 may receive the duplicate transmissions and may store the frames, for example, in pppbbttsssrrrrpppppp. Since additional frames can be accumulated, for example, in high interference areas, the portable device will continue to search for the sync bits and finally locate the sync bits as part of the decoded frame. Of course, the data may be buffered at the drill rig or any other suitable location for decoding purposes. It should be noted that averaging 4 packets or frames can reduce noise by a factor of two. The foregoing example uses 5 bits for scrolling (32 values for 24 clock positions) and 11 bits for pitch, covering +/-45 deg. or +/-100% levels at 0.1% resolution. As described above and listed in table 3, non-linear pitch coding can reduce the number of bits required to cover the +/-45 range by using a small number of data bits (e.g., using 9 data bits instead of 11 bits).

In another embodiment, when step 512 detects that the subterranean tool is not rotating and/or stationary, the transmission of the rolling data packets may be suspended as part of the overall stationary data packet structure. Transmission of the rolling data packets may resume in response to detecting that the inground tool is at least rotating. In some embodiments, advancement of the inground tool is inhibited until a rolling data packet is received during rotation.

Attention is now directed to FIG. 5, which is a flow chart illustrating an embodiment of a method, indicated generally by the reference numeral 600, for dynamically invoking a fixed packet length for ensemble averaging in response to an operational state of an inground tool. The method begins at 604 and proceeds to 608 where various data structures that are employed based on the operational state of the inground tool are initialized at 608. For example, when the underground tool is moving, the roll orientation may be indicated with 8 roll positions according to table 1, while the pitch orientation may be indicated according to, for example, table 2. A fixed length packet structure may be applied when the inground tool is not moving, e.g., consistent with the foregoing description. Operation then moves to 612 which determines the operational status of the inground tool whether it is in motion or stationary. As described above, in one embodiment, this determination is made by monitoring the accelerometer output for a short period of time. If the drill is found to be moving, operation proceeds to 616, where the dynamic packet structure is invoked, for example, according to tables 1 and 2. At 620, the data packet is transmitted. Operation then returns to 612. When the latter step determines that the inground tool is stationary, operation proceeds to 624 which initializes a fixed length packet structure. At 628, the fixed length data packets are repeatedly/repetitively transmitted for receipt by a portable device or other suitable hardware on the surface. At 632, a fixed length packet is received and may be added to the buffer in the manner described above. Decoding of the buffer values may be attempted at 636, for example, for each repetition. In other embodiments, the portable device may delay any attempt to decode until a predetermined amount of data has accumulated in the buffer. For each iteration, if the decode is unsuccessful, operation returns to step 632 where the next packet is received. Once a successful decode is obtained, operation proceeds to 640, which transfers the decoded value to the appropriate location, after which the buffer is cleared. Thereafter, operation returns to 612.

As described above and with reference to FIG. 2, the accelerometer 220 is subject to a high degree of shock and vibration. To provide a real-time rolling reading while drilling, in one embodiment, the processor 210 may apply a continuous filter to the raw rolling data to smooth shock and vibration induced variations. For example, the rate filtering may remove roll variations that vary faster than +/-3 ° per second. The +/-3 deg. per second value of the present example is not necessary, but it is derived from the fact that the drill pipe from which the drill string is made exhibits a limited bend radius, so that the tool housing cannot change pitch or direction without going through some limited distance. For example, if R is the limiting bend radius of the drill pipe, S is the arc length of the tool travel and Δ (θ) is the change in pitch angle:

r ═ Sx θ (equation 1)

If R is 100ft and θ is 3 °, S is 5.236 ft. The +/-3 deg. per second is sufficient unless the rate of penetration is faster than 3.57mph during the turn.

In another embodiment, the pitch angle while drilling may be averaged by switching to a higher g-sensor (i.e., accelerator) as the downhole tool rotates and/or moves. When drilling rock, the shock and vibration on the case of an underground tool can be hundreds of grams. The measurement range of conventional MEMS accelerometers, typically used for horizontal directional drilling applications, is typically limited to +/-2g due to the need for high resolution. Due to this limited dynamic range, such an accelerometer will constantly encounter its upper and lower limits depending on the drilling conditions. Under the adverse conditions of limited dynamic range, it is difficult to obtain meaningful average pitch even if averaging is applied to the pitch data. Thus, a low cost, high g, low resolution accelerometer 660 (FIG. 2) may be added to the sensor array to track average pitch as the underground tool rotates. In another embodiment, a MEMS accelerometer with a programmable g-range may be used so that the pitch range can be adapted in real time when conditions are warranted.

Turning now to FIG. 6, FIG. 6 is a flow chart illustrating an embodiment of a method, indicated generally by the reference numeral 700, for dynamically customizing g-force sensing to increase dynamic range based on operating conditions in which the inground tool is operating. The method begins at 704 and proceeds to 708 where an initialization sensing is performed at 708 with a high resolution limited range g-force sensor or a high resolution sensor range when a programmable sensor is used. At 712, g-force readings (i.e., accelerometer readings) are obtained. At 716, the reading is compared to a threshold value set based on the operating range performance of the currently used accelerometer. If the current reading is within range, the method continues to use the high resolution range at 720 and transmit the reading at 724 in normal operation. On the other hand, if step 716 detects that the current g-force reading exceeds the threshold, then operation proceeds to 728, where a transition is made from the high-resolution sensor to the high-g-force, low-resolution sensor. Thereafter, operation proceeds to 724 so that the pitch readings from the high resolution sensor can be averaged as a whole for use by the system and/or display to the operator of the portable device and/or drilling rig. As part of normal operation, the process iteratively loops back to step 712 to obtain the next accelerometer reading.

The foregoing description of the invention has been presented for purposes of illustration and description. It is not intended to be exhaustive or to limit the invention to the precise form or forms disclosed, and other modifications and variations are possible in light of the above teachings. For example, the data protocol described above may be selected manually or automatically. In one embodiment, one or more of the advanced data protocols used to make the extended range and/or provide tamper resistance may be selected from portable locators, other above ground equipment, or from the drilling rig. In another embodiment, one or more of the advanced data protocols may be selected based on the pitch orientation of the transmitter at startup. In another embodiment, one or more of the advanced data protocols may be selected based on a sequence of drill string roll orientations. Accordingly, those skilled in the art should be able to recognize certain modifications, permutations, additions and combinations of the above-described embodiments.

Preferably comprising all of the elements, portions and steps described herein. It will be understood by those skilled in the art that any of these elements, portions and steps may be replaced by other elements, portions and steps or deleted entirely.

As a short summary, the written disclosure includes at least the following sections. A transmitter is positioned proximate to the inground tool for sensing a plurality of operating parameters associated with the inground tool. The transmitter customizes the data signal to characterize one or more operating parameters transmitted from the inground tool based on the operational status of the inground tool. A receiver receives the data signal and recovers the operating parameters. Advanced data protocols are described. Pitch averaging and an increase in dynamic pitch range based on accelerometer readings monitoring mechanical shock and vibration of an inground tool are described.

Conception of

At least the following concepts are further defined herein.

Concept 1. an apparatus for use in conjunction with a system for performing an inground operation in which a drill string extends from a drill rig to an inground tool such that extension and retraction of the drill string generally produces corresponding movement of the inground tool during the inground operation, said apparatus comprising:

a transmitter configured to be disposed proximate to the inground tool for sensing a plurality of operating parameters associated with the inground tool and customizing the data signal to characterize one or more of the operating parameters transmitted from the inground tool based upon the inground tool operating condition; and

a receiver, positioned at the surface location, for receiving the data signal and recovering the operating parameters.

Concept 2. the apparatus of concept 1, wherein the transmitter is configured to determine the operational status of the inground tool based on detecting at least one of movement and rotation of the inground tool.

Concept 3. the apparatus of concept 1 or 2, wherein the transmitter and receiver are configured to cooperatively utilize a plurality of communication protocols to transmit and receive the digital signals, respectively, and the transmitter is configured to change the communication protocol in response to detecting the change in the operational state of the inground tool.

Concept 4. the apparatus of concept 3, wherein the transmitter is configured to detect at least a change in the following operating conditions: (i) changes from static to dynamic and (i i) changes from dynamic to static.

Concept 5 the apparatus of concept 3 or 4, wherein the plurality of communication protocols comprises a static pitch resolution protocol and a dynamic pitch resolution protocol.

Concept 6. the apparatus of concept 5, wherein the resolution of the static pitch resolution protocol is higher than the resolution of the dynamic pitch resolution protocol.

Concept 7. the apparatus of concept 5 or 6, wherein at least one of the dynamic pitch resolution protocol and the static pitch resolution protocol comprises a pitch orientation representative of a resolution based transmitter, the resolution decreasing in one or more steps in response to an increase in magnitude of the pitch orientation.

Concept 8 the apparatus of concept 7, wherein the static pitch resolution protocol characterizes the pitch orientation based on a fixed number of bits defining a fixed number of bit values, and the step defines at least two pitch ranges, the pitch ranges being assigned the bit values to establish a resolution for each pitch range.

Concept 9. the device of any one of concepts 3 to 8, wherein the transmitter is configured to detect a quiescent state thereof and, in response thereto, to convert to fixed length data packets to characterize the one or more operating parameters, and thereafter to repeatedly transmit the fixed length data packets for reception by the receiver during the quiescent state.

Concept 10 the apparatus of concept 9, wherein the transmitter is further configured to include at least one of a roll orientation, a pitch orientation, a battery status, and a temperature of the transmitter as the operational parameter of the characterized fixed-length data packet.

Concept 11 the apparatus of concept 9 or 10, wherein the receiver is configured to perform an ensemble averaging of the reception of the plurality of fixed length data packets to recover the characterized operating parameter.

Concept 12. apparatus according to any of the preceding concepts, wherein the operating parameter comprises a roll orientation of the transmitter, and the transmitter is configured to transmit the data signal using a data packet structure comprising a plurality of different types of data packets to characterize the plurality of operating parameters comprising at least a roll orientation data packet specifying the roll orientation in response to detecting that the inground tool is rotating, and to suspend transmission of the roll orientation data packet from the data packet structure in response to detecting that the inground tool is not rotating.

Concept 13 the apparatus of any preceding concept, wherein one of the operating parameters is a pitch orientation of the inground tool and the transmitter is configured to transmit the data signal using a packet protocol that includes low resolution pitch packets in response to detecting that the inground tool is dynamic and to transmit the data signal using a packet protocol that includes high resolution pitch packets in response to detecting that the inground tool is static.

Concept 14. apparatus according to any of the preceding concepts, wherein the data signal is constructed based on a data packet protocol for transferring a series of data packets from a transmitter to a receiver to characterize one or more operating parameters such that each data packet comprises at least two synchronization bits for decoding each data packet at the receiver while the synchronization bits simultaneously serve as one data bit to characterize one or more of the operating parameters along with other bits.

Concept 15 the apparatus of concept 14, wherein the operating parameter is a roll orientation of the inground tool.

Concept 16. a transmitter for use in conjunction with a receiver as part of a system for performing an inground operation in which a drill string extends from a drill rig to an inground tool that supports the transmitter such that extension and retraction of the drill string generally produces corresponding movement of the inground tool during the inground operation, said transmitter comprising:

at least one sensor for sensing one or more operating parameters related to the operational status of the inground tool; and

a processor configured to customize the data signal transmitted from the transmitter based on the operational status of the inground tool.

Concept 17 a receiver for use in conjunction with a transmitter as part of a system for performing an inground operation in which a drill string extends from a drill rig to an inground tool that supports the transmitter such that extension and retraction of the drill string generally produces corresponding movement of the inground tool during the inground operation, said receiver comprising:

means for receiving a data signal transmitted by the transmitter, the data signal characterizing one or more operating parameters associated with an operating condition of the inground tool such that the data signal is customized based on the operating condition; and

a processor configured to decode the customized data signal to recover one or more operating parameters.

Concept 18. a transmitter for use in conjunction with a system for performing an inground operation in which a drill string extends from a drill rig to an inground tool such that extension and/or rotation of the drill string moves the inground tool along an inground path while being subjected to mechanical shock and vibration, said transmitter comprising:

an accelerometer for sensing a pitch orientation of the inground tool when subjected to mechanical shock and vibration in each of a high resolution range and a low resolution range to produce a series of pitch readings; and

a processor configured to monitor the series of pitch readings and in response thereto, select one of a high resolution range and a low resolution range to characterize the pitch orientation, and average the series of pitch readings in a range selected from the high resolution range and the low resolution range to produce an average pitch reading transmitted from the transmitter.

Concept 19 the transmitter of concept 18, wherein the accelerometer arrangement comprises a high-g-force, low-resolution accelerometer for producing a series of pitch readings in a high resolution range, and a low-g-force, high-resolution accelerometer for producing a series of pitch readings in a low resolution range.

Concept 20 the transmitter of concept 18, wherein the accelerometer arrangement comprises a programmable accelerometer for providing a high resolution range and a low resolution range responsive to the processor.

Concept 21 the transmitter of concept 18 or 1, wherein the processor is configured to switch between the high resolution range and the low resolution range based on a g-force threshold.

Concept 22. a transmitter for use in conjunction with a system for performing an inground operation in which a drill string extends from a drill rig to an inground tool such that extension and/or rotation of the drill string moves the inground tool along an inground path while being subjected to mechanical shock and vibration, said transmitter comprising:

an accelerometer for sensing a pitch orientation of the inground tool to produce a series of pitch readings; and

a processor configured to average the series of pitch readings to produce an average pitch reading transmitted from the transmitter.

Concept 23 the transmitter of concept 22 further configured to continuously filter the series of pitch readings to reduce variations in the average pitch reading in response to mechanical shock and vibration.

Concept 24 the transmitter of concept 23, wherein the processor is configured to remove pitch changes in the series of pitch readings that indicate a rate of change in pitch orientation is greater than a predetermined value.

Concept 25. a transmitter for use in conjunction with a receiver as part of a system for performing an inground operation in which a drill string extends from a drill rig to an inground tool that supports the transmitter such that extension and retraction of the drill string generally produces corresponding movement of the inground tool during the inground operation, said transmitter comprising:

at least one sensor for sensing one or more operating parameters associated with the inground tool; and

a processor configured to transmit data relating to one or more operating parameters in a standard mode and an alternate mode, the alternate mode characterizing at least one particular operating parameter using a smaller number of bits than the standard mode characterizing the particular parameter, and the alternate mode representing the particular parameter at a lower resolution than the standard mode.

Concept 26 the transmitter of concept 25, wherein the particular operating parameter is a roll orientation of the inground tool and the transmitter is configured to transmit the data signal using a packet protocol that includes a higher resolution roll packet in the standard mode and a lower resolution roll packet in the alternative mode.

Concept 27 the transmitter of concept 26, wherein the standard mode represents 24 scroll positions and the alternative mode represents 8 scroll positions.

Concept 28 the transmitter of concept 25, wherein the particular parameter is a pitch orientation having a magnitude and being in at least one of a normal mode and an alternate mode, the pitch orientation resolution decreasing in one or more steps in response to an increase in the magnitude of the pitch orientation.

Concept 29 the transmitter of concept 25, wherein the specific operating parameter is a roll orientation of the transmitter, and the transmitter is configured to transmit the data signal using a data packet structure comprising a plurality of different types of data packets to characterize the plurality of operating parameters comprising at least a specified roll orientation in the standard mode, and to suspend transmission of roll orientation data packets in the alternative mode.

Concept 30 the transmitter of concept 25, wherein the particular operating parameter is a pitch orientation of the inground tool and the transmitter is configured to transmit the data signal using a packet protocol that includes high resolution pitch packets in the standard mode and transmit the data signal using a packet protocol that includes low resolution pitch packets in the alternative mode.

Concept 31 the transmitter of any of concepts 25-30, further configured to switch to the alternating mode based on the detected electromagnetic interference.

Concept 32. a transmitter for use in conjunction with a receiver as part of a system for performing an inground operation in which a drill string extends from a drill rig to an inground tool that supports the transmitter such that extension and retraction of the drill string generally produces corresponding movement of the inground tool during the inground operation, said transmitter comprising:

at least one sensor for sensing one or more operating parameters associated with the inground tool; and

a processor configured to transmit a data signal from the transmitter using a plurality of data packet communication protocols, the plurality of data packet communication protocols including a particular protocol that characterizes one or more operating parameters with a fixed data frame and repeatedly transmits the fixed data frame in response to detecting that the transmitter is in a quiescent state.

Concept 33. the transmitter according to concept 32, configured to include at least one of a roll orientation, a pitch orientation, a battery status, and a temperature of the transmitter of the fixed data frame.

Claims (32)

1. An apparatus for use in conjunction with a system for performing an inground operation in which a drill string extends from a drill rig to an inground tool such that extension and retraction of the drill string produces corresponding movement of the inground tool during the inground operation, said apparatus comprising:

a transmitter configured to be disposed proximate to the inground tool for sensing a plurality of operating parameters associated with the inground tool for detecting whether the operational status of the inground tool is stationary or in motion and a change in the operational status and transmitting data that characterizes one or more of the operating parameters at a first resolution level when the inground tool is stationary and at a second resolution level when the inground tool is in motion, wherein the first resolution level is higher than the second resolution level; and

a receiver positioned at a surface location for receiving the data signal and recovering the operating parameters.

2. The apparatus of claim 1, wherein the transmitter is configured to determine a motion-related operational status of the inground tool based on detecting at least one of movement and rotation of the inground tool.

3. The apparatus of claim 1, wherein the transmitted data characterizing one or more of the operating parameters comprises a static pitch resolution protocol and a dynamic pitch resolution protocol.

4. The apparatus of claim 3, wherein the resolution of the static pitch resolution protocol is higher than the resolution of the dynamic pitch resolution protocol.

5. The apparatus of claim 3, wherein at least one of the dynamic pitch resolution protocol and the static pitch resolution protocol comprises a pitch orientation representative of the transmitter based on a resolution that decreases in one or more steps in response to an increase in magnitude of the pitch orientation.

6. The apparatus of claim 5, wherein the static pitch resolution protocol characterizes pitch orientation based on a fixed number of bits defining a fixed number of bit values, and the step defines at least two pitch ranges, the pitch ranges being assigned the bit values to establish a resolution for each pitch range.

7. The apparatus of claim 1, wherein the transmitter is configured to detect a quiescent state thereof and, in response thereto, to convert to fixed length packets to characterize the one or more operating parameters, and thereafter repeatedly transmit the fixed length packets for reception by the receiver during the quiescent state.

8. The apparatus of claim 7, wherein the transmitter is further configured to include at least one of a roll orientation, a pitch orientation, a battery state, and a temperature of the transmitter as the characterized operating parameter of the fixed-length data packet.

9. The apparatus of claim 7, wherein the receiver is configured to ensemble average multiple receptions of the fixed length data packets to recover the characterized operating parameters.

10. The apparatus of claim 1, wherein the operating parameter comprises a roll orientation of the transmitter, and the transmitter is configured to transmit a roll orientation data packet specifying the roll orientation when the inground tool is rotating, and to suspend transmission of the roll orientation data packet when the inground tool is not rotating.

11. The apparatus of claim 1, wherein one of the operating parameters is a pitch orientation of the inground tool, and the transmitter is configured to transmit a low resolution pitch data packet in response to detecting that the inground tool is in motion and a high resolution pitch data packet in response to detecting that the inground tool is stationary.

12. The apparatus of claim 1, wherein the data is constructed based on a packet protocol for transferring a series of packets from the transmitter to the receiver to characterize one or more operating parameters such that each packet includes at least two synchronization bits for decoding each packet at the receiver while synchronization bits are simultaneously used as one data bit to characterize one or more of the operating parameters along with other bits.

13. The apparatus of claim 12, wherein the operating parameter is a roll orientation of the inground tool.

14. A transmitter for use in conjunction with a receiver as part of a system for performing an inground operation in which a drill string extends from a drill rig to an inground tool that supports the transmitter such that extension and retraction of the drill string produces corresponding movement of the inground tool during the inground operation, said transmitter comprising:

at least one sensor for sensing one or more operating parameters associated with the inground tool; and

a processor configured to detect whether the inground tool is stationary or in motion based on the sensor input, and transmit data that characterizes one or more of the operating parameters at a first resolution level when the inground tool is stationary and at a second resolution level when the inground tool is in motion, wherein the first resolution level is higher than the second resolution level.

15. A transmitter for use in conjunction with a system for performing subterranean operations in which a drill string extends from a drill rig to a subterranean tool such that extension and/or rotation of the drill string moves the subterranean tool along a subterranean path while being subjected to mechanical shock and vibration, the transmitter comprising:

an accelerometer for sensing a pitch orientation of the inground tool when subjected to mechanical shock and vibration in each of a high resolution range and a low resolution range to produce a series of pitch readings; and

a processor configured to monitor the series of pitch readings and in response thereto, select one of a high resolution range and a low resolution range to characterize pitch orientation, and average the series of pitch readings in a range selected from the high resolution range and the low resolution range to produce an average pitch reading transmitted from the transmitter.

16. The transmitter of claim 15 wherein the accelerometer arrangement comprises a high-g-force, low-resolution accelerometer for producing a series of pitch readings in the high resolution range, and a low-g-force, high-resolution accelerometer for producing a series of pitch readings in the low resolution range.

17. The transmitter of claim 15 wherein the accelerometer arrangement includes a programmable accelerometer for providing a high resolution range and a low resolution range responsive to the processor.

18. The transmitter of claim 15, wherein the processor is configured to switch between a high resolution range and a low resolution range based on a g-force threshold.

19. A transmitter for use in conjunction with a system for performing subterranean operations in which a drill string extends from a drill rig to a subterranean tool such that extension and/or rotation of the drill string moves the subterranean tool along a subterranean path while being subjected to mechanical shock and vibration, the transmitter comprising:

an accelerometer for sensing a pitch orientation of the inground tool to produce a series of pitch readings; and

a processor configured to average the series of pitch readings to produce an average pitch reading transmitted from the transmitter and to continuously filter the series of pitch readings to reduce variations in the average pitch reading in response to mechanical shock and vibration.

20. The transmitter of claim 19 wherein the processor is configured to remove pitch changes in the series of pitch readings that indicate a rate of change in pitch orientation greater than a predetermined value.

21. A transmitter for use in conjunction with a receiver that is part of a system for performing an inground operation in which a drill string extends from a drill rig to an inground tool that supports the transmitter such that extension and retraction of the drill string produces corresponding movement of the inground tool during the inground operation, said transmitter comprising:

at least one sensor for sensing one or more operating parameters associated with the inground tool; and

a processor configured to transmit data relating to the one or more operating parameters in a standard mode and a replacement mode, the replacement mode characterizing at least one particular one of the operating parameters using a smaller number of bits than the standard mode characterizing the particular one of the operating parameters, and the replacement mode representing the particular one of the operating parameters at a lower resolution than the standard mode.

22. The transmitter of claim 21, wherein the particular one of the operating parameters is a roll orientation of the inground tool, and the transmitter is configured to transmit the data using a higher resolution roll data packet in the standard mode and transmit the data using a lower resolution roll data packet in the alternative mode.

23. The transmitter in claim 22, wherein the standard mode represents 20 scroll positions and the alternate mode represents 8 scroll positions.

24. The transmitter of claim 21 wherein the particular one of the operating parameters is a pitch orientation having a magnitude and being in at least one of a standard mode and a replacement mode, the pitch orientation resolution decreasing in one or more steps in response to an increase in the magnitude of the pitch orientation.

25. The transmitter of claim 21, wherein the particular one of the operating parameters is a roll orientation of the transmitter, and the transmitter is configured to transmit the data using a roll orientation data packet specifying the roll orientation in the standard mode, and to suspend transmission of the roll orientation data packet in the alternate mode.

26. The transmitter of claim 21 wherein the particular one of the operating parameters is a pitch orientation of the inground tool and the transmitter is configured to transmit the data using high resolution pitch data packets in the standard mode and transmit data signals using a packet protocol that includes low resolution pitch data packets in the replacement mode.

27. The transmitter of claim 21, further configured to switch to the alternate mode based on the detected electromagnetic interference.

28. A transmitter for use in conjunction with a receiver that is part of a system for performing an inground operation in which a drill string extends from a drill rig to an inground tool that supports the transmitter such that extension and retraction of the drill string produces corresponding movement of the inground tool during the inground operation, said transmitter comprising:

at least one sensor for sensing one or more operating parameters associated with the inground tool; and

a processor configured to transmit data signals using a plurality of data packet communication protocols, the plurality of data packet communication protocols including a particular protocol that characterizes the one or more operating parameters with a fixed data frame and repeatedly transmits the fixed data frame in response to detecting that the transmitter is in a quiescent state.

29. The transmitter of claim 28, configured to include at least one of a roll orientation, a pitch orientation, a battery status, and a temperature of the transmitter in the fixed data frame.

30. An apparatus for use in conjunction with a system for performing an inground operation in which a drill string extends from a drill rig to an inground tool such that extension and retraction of the drill string produces corresponding movement of the inground tool during the inground operation, said apparatus comprising:

a transmitter configured to be disposed proximate the inground tool for sensing a plurality of operating parameters related to the inground tool, said operating parameters including a roll orientation of said transmitter, and said transmitter for transmitting a data signal including a roll orientation data packet specifying said roll orientation in response to detecting rotation of the inground tool and for suspending transmission of said roll orientation data packet in response to detecting no rotation of the inground tool; and

a receiver positioned at a surface location for receiving the data signal and recovering the operating parameters.

31. An apparatus for use in conjunction with a system for performing an inground operation in which a drill string extends from a drill rig to an inground tool such that extension and retraction of the drill string produces corresponding movement of the inground tool during the inground operation, said apparatus comprising:

a transmitter configured to be disposed proximate the inground tool for sensing a plurality of operating parameters related to the inground tool, said operating parameters including a pitch orientation of said transmitter, and said transmitter for transmitting a data signal including a low resolution pitch data packet in response to detecting that the inground tool is in motion and transmitting a high resolution pitch data packet in response to detecting that the inground tool is stationary; and

a receiver positioned at a surface location for receiving the data signal and recovering the operating parameters.

32. An apparatus for use in conjunction with a system for performing an inground operation in which a drill string extends from a drill rig to an inground tool such that extension and retraction of the drill string produces corresponding movement of the inground tool during the inground operation, said apparatus comprising:

a transmitter configured to be disposed proximate to the inground tool for sensing a plurality of operating parameters related to the inground tool and transmitting a data signal from the inground tool based on a data packet protocol that transfers a series of data packets from the transmitter to characterize one or more of the operating parameters such that each data packet includes at least two synchronization bits for decoding each data packet while the synchronization bits serve as one data bit to characterize one or more of the operating parameters along with other bits; and

a receiver positioned at a surface location for receiving the data signal and recovering the operating parameters.