CN107203592A - A kind of pushed information based on three-point fox method accepts and believe detection method - Google Patents

Abstract

The invention relates to a push information detection method based on a three-point positioning method, which uses the objective factor of position information in subjective messages as an evaluation reference, without adding new evaluation standards, effectively reduces the complexity of the inspection process, and applies three-point positioning With the assistance of the positioning function of the electronic map in the smart phone, an important distance calculation algorithm is given based on the geometric scanning algorithm, which preliminarily determines the area where the information provider is located, and compares it with the area where the information occurs. The coarse-grained reliable timeliness information.

Description

A push information detection method based on three-point positioning method

technical field

The invention belongs to the technical field of Android platform positioning, and in particular relates to a push information detection mechanism based on a three-point positioning method.

Background technique

(1) Positioning Technology

From a technical point of view, the positioning technology of domestic mobile devices can be divided into the following three categories:

1) Network positioning. Network positioning has relatively low hardware and software requirements for devices, as long as they can be connected to the network. Therefore, the accuracy of the geographic location obtained through network positioning cannot be well guaranteed. Network positioning can be subdivided according to different networks. Common ones include base station positioning and Wi-Fi positioning. The farther the mobile phone is from the base station, the weaker the signal will be, and the closer to the base station, the stronger the signal will be. Base station positioning is to obtain the distance and angle between the device and the base station by calculating the time when the information sent by the device arrives at each base station. Since the locations of the base stations are constructed by various mobile communication operators, their locations are known and definite. Therefore, according to the location of the base station and the measured distance and angle, the location information of the device can be calculated. Wi-Fi positioning is also called Wi-Fi hotspot positioning. It relies on the existing wlan network, adopts the RSS positioning method, and uses a fixed-position wireless AP (Access Point, commonly known as "hot spot"). Each wireless hotspot has a globally unique MAC address, and generally speaking, within a period of time, this wireless hotspot will not move. However, the location of wireless hotspots is not obtained through precise on-site measurements. When a device turns on the Wi-Fi function, it can search many Wi-Fi hotspots, no matter whether it is encrypted or not, whether it is connected or not, it can also measure the signal strength of each hotspot, and at the same time know the SSID of each hotspot ( Service Set Identifier, service set identifier) and MAC (Media Access Control or Medium Access Control, media access control, or called physical address) address. When the device turns on the GPS function, the device will send the data capable of marking hotspots to the location server of the location service provider. This forms a large database of hotspot coordinates. If a hotspot can be continuously collected, the coordinates of this hotspot will be iterated continuously as the number of collections increases, and its coordinates will become more and more accurate. When a device turns on Wi-Fi for positioning, the server can obtain the MAC address and signal strength of the surrounding Wi-Fi. Using this information, search in the database, you can find out the location.

2) GPS positioning. GPS (Global Position System, Global Positioning System) is a system composed of 24 satellites covering the earth. GPS positioning is to obtain the location information of the device through the communication between the device and the GPS satellite. Four satellites can be observed at any time at any place, so this positioning method has high accuracy. However, GPS positioning has relatively higher hardware and software requirements for mobile devices, and must have a built-in GPS module. Power consumption is also a shortcoming of it.

3) Hybrid positioning. Hybrid positioning is the comprehensive use of integrated network positioning and GPS positioning. The hybrid positioning technology integrates the advantages of these two positioning technologies and learns from each other. While the speed of positioning is improved, the accuracy of positioning is also improved. The improvement of positioning speed and accuracy will lead to more corresponding expansion services. Therefore, hybrid positioning technology is the development trend after positioning technology (Shi Ting, 2014).

(2) Map service

Location-dependent business is developing very fast, including every corner of business, medicine, work and life. These services provide users with a series of services such as positioning, tracking and alerting of sensitive areas. For example, Google Maps, Baidu Maps, etc., all need to use location services.

Electronic maps are also called digital maps. Different from ordinary paper maps, electronic maps use computer technology to store and browse digitally. The user's location information can be obtained by using the map database through the network. The characteristics of electronic maps are that they are easy to operate, not restricted by time and region, and can be sent to any place using data (Shi Ting, 2014). Compared with traditional paper maps, electronic maps are cheap, fast to update, and can be interactive. The use of virtual reality technology to realize the three-dimensional map makes people enjoy more visually.

Two-dimensional maps are common in electronic maps. The most important thing in developing an electronic map is to combine a large amount of geographic information data. Data structures and models are the basis of complete electronic map development. The data structure includes vector structure, raster structure and vector-raster integration structure, which are used to illustrate the logical structure and physical storage method of the information on the map in the computer. Data models include relational data models, object-oriented data models, and other data models such as spatiotemporal data models and multimedia data models.

In daily life, electronic maps play a very important role. Users can query the location of any place and find the best way and route to travel through the electronic map. Through the electronic map, it is also possible to know information other than the detailed location, such as brief introduction, contact information, and user evaluation. It is also possible to send messages, publicize and interact through the electronic map.

(3) Map module Android SDK

The map module Android SDK is an application program interface launched by Baidu Maps for Android 2.1 and above devices. Developers can use this interface to obtain the services and data provided by Baidu Maps to implement map applications based on Android mobile devices. At present, the map module Android SDK provides characteristic functions such as basic map, POI retrieval, geocoding, ranging, navigation, positioning, offline map, peripheral radar, LBS cloud, and personalized map, as shown in Figure 1, and Table 1 shows the features of the present invention Mainly used map module functions in Android SDK.

1) Search service: Baidu Maps SDK provides a variety of search services, including location search, surrounding search, bus search, etc. Initialize the MKSearch class, register the monitoring object MKSearchListener of the retrieval results, and then complete the retrieval service asynchronously. After the search business application is finished, you need to use the destroy() method of MKSearch to release the resource occupation.

2) Point of interest (POI) search: refers to within a specific rectangular area, according to the specific keywords set by the developer, 1. Use the poiSearchInbounds(String key, GeoPointptLB, GeoPointptRT) method to retrieve POI information; 2. Use The poiSearchInCity(String city,String key) method can search for POI information in a city; 3. With the specified coordinate point as the center, query all POIs within a certain radius according to a given keyword. The application method is poiSearchNearBy( String key, GeoPointpt, intradius). The search result will be displayed through onGetPoiResult of MySearchListener.

Table 1 Some functions of map module Android SDK

3) Address information query: query address information according to geographic coordinates, and implement reverse geocode and geocode through reverseGeocode() and geocode() methods. The return results of address resolution and reverse address resolution are in the onGetAddrResult() method in MKSearchListener. According to whether the type field in MKAddrInfo is MKAddrInfo.MK_GEOCODE or MKAddrInfo.MK_REVERSEGEOCODE, it is necessary to specifically distinguish whether it is the result of reverse geocoding or the result of geocoding.

4) Timely search suggestions: According to the keywords retrieved, suggested words are given online. It is implemented through the suggestionSearch(String key, String city) method. The parameter key is the keyword, and the parameter city is the search city.

Contents of the invention

Aiming at the inability of the media and the public to judge whether the information published in social media is credible, the present invention aims at using the objective factor that cannot be artificially changed—location information, and designs a push information collection and setting detection mechanism based on the three-point positioning method to realize the authenticity of the message. The detection of credibility strives to achieve the goal of "the correct information occurs at the correct position at the correct time".

The technical solution provided by the present invention is a push information acquisition setting detection mechanism based on the three-point positioning method, which includes the following steps:

A kind of push information acceptance detection method based on three-point positioning method, it is characterized in that, comprises the following steps:

Step 1, build the Android system development environment, specifically:

Configure the Android development environment: install JDK and configure the variable environment of JDK on Windows, then download Eclipse and configure environment variables, then download and install the Android SDK, and finally install the ADT plug-in for Eclipse

Map module Android SDK: Create a libs folder in the project, copy the files in the development kit to the libs directory and integrate it into your own project.

Step 2, based on the Activity application program on the mobile terminal of the Android system, design the detection mechanism structure and realize the main interface module. The logical structure of the entire detection mechanism can be divided into three layers: the presentation layer, the logic processing layer and the data storage layer.

Presentation layer: Provide the message sender's software interaction page, including software setting page, message sending page and map display page.

Logic processing layer: Responsible for all data processing and data transmission of the entire detection mechanism of the system. Including the processing of parameter modification, the calculation of the distance between the message sender and the distance measuring point, the processing of the location of the message sender, and the judgment of the message credibility.

Data storage layer: mainly realizes the reception and storage of information reported by information reporters.

Step 3, based on the push information detection mechanism of the three-point positioning method, realize the detection of push information,

Step 3.1: Locate the user who opened the application and obtain location information, that is, set a location change condition through the requestLocationUpdates() object. This condition includes the minimum time interval when the positioning request is initiated, and the minimum displacement change when the positioning request is initiated. These two conditions must be met at the same time to execute the callback function and trigger the location monitoring. Avoid useless positioning repeated many times. Manually perform removeUpdates() to update the location information, keep tracking in onResume(), and turn off tracking in onPause() accordingly.

Step 3.2, when the user sends a message, judge whether the message is empty, and at the same time query the location of the message to avoid sending blank information and invalid information;

In step 3.3, the three-point positioning method calculates the distance between the measurement points and draws a circle.

Step 3.4, information detection, based on the geometric scanning algorithm, proposes and adopts an algorithm for calculating the distance between the place where the reported message occurs and the area where the message sender is located.

In the above-mentioned push information detection method based on the three-point positioning method, the implementation method of step 3.3 is to use the Baidu map drawing circle API class Circle to create a circle overlay, and a circle can be added through map.addOverlay(circle), and others The method personalizes the graphics drawn.

In the above-mentioned push information detection method based on the three-point positioning method, the implementation method of step 3.4 is to conduct research on the points in the address space according to the geometric scanning algorithm. The algorithm of the distance between regions, input the three reconnaissance points S1, S2, S3 and the distances L1, L2, L3 between them and the message sender, and the place where the news happened P, then you can get the place where the news happened and the area where the news reporter is located The distance L between.

The present invention has the following advantages: using the objective factor of position information in subjective information as an evaluation reference, without adding new evaluation criteria, and reducing the complexity of the inspection process; at the same time, it can also be used in combination with other evaluation systems, and has scalability; The positioning function common in popular smart phones makes this technology very convenient. At the same time, the detection results can be obtained when the message is sent and received, which is timely; a grading system for credibility evaluation is proposed for future research provides direction for development.

Description of drawings

Fig. 1 is the development resource provided by the map module Android SDK of the embodiment of the present invention.

Fig. 2 is a flow chart of implementing the message detection mechanism based on the three-point positioning method according to the embodiment of the present invention.

FIG. 3 is a basic architecture diagram of the Android platform of the embodiment of the present invention.

Fig. 4 is an Android project directory diagram of the embodiment of the present invention.

Fig. 5 is a diagram of permission information added to the Android project directory according to the embodiment of the present invention.

Fig. 6 is a map control diagram added in the layout xml file of the embodiment of the present invention.

Fig. 7 is a life cycle diagram of the embodiment of the present invention.

Fig. 8 is an import-related class diagram of the embodiment of the present invention.

Fig. 9 is a flow chart of detecting the credibility of instant information through the three-point positioning method according to the embodiment of the present invention.

Fig. 10 is a logical structure diagram of the detection mechanism of the embodiment of the present invention.

Fig. 11 is the experimental main interface diagram of the embodiment of the present invention.

Fig. 12 is a coordinate system diagram of Baidu map picking according to the embodiment of the present invention.

Fig. 13 is a diagram of the application setting page of the embodiment of the present invention.

Fig. 14 is a successful diagram of setting measurement point coordinates according to the embodiment of the present invention.

Fig. 15 is a successful diagram of restoring the default measurement point coordinates according to the embodiment of the present invention.

Fig. 16 is a diagram of avoiding blank information and invalid information according to the embodiment of the present invention.

Fig. 17 is a message detection page diagram of the embodiment of the present invention.

Fig. 18 is a page diagram of "disaster scene" positioning according to the embodiment of the present invention.

Fig. 19 is a circular tangent division diagram of the embodiment of the present invention.

Fig. 20 is a two-dimensional geometric scan diagram of an embodiment of the present invention.

Fig. 21 is a scanning diagram of the three-point positioning algorithm of the embodiment of the present invention.

Fig. 22 is a diagram of test results of Wuhan University in the embodiment of the present invention.

detailed description

The implementation flow of the message detection mechanism based on the three-point positioning method designed by the present invention is shown in Figure 2, and the automatic operation of the flow can be realized by those skilled in the art by using computer software technology. The specific implementation process of the embodiment is as follows:

Step 1, build the Android system development environment, configure the Android development environment and map module AndroidSDK;

The Android development environment is mainly divided into the following four steps:

(1) Install JDK and configure the variable environment of JDK on Windows;

(2) Download and install Eclipse, configure environment variables;

(3) Download and install the Android SDK;

(4) Install the ADT plug-in for Eclipse.

JDK (Java SE Development Kit) is a software development kit for the Java language. JDK is the focus of the Java development process, including the Java development execution environment (Java Runtime Environment), a series of Java development tools, and the Java class library called by developers when developing applications. The basic tools included in the JDK are shown in Table 2. These tools can be viewed in the bin directory under the JDK installation directory.

Table 2 Basic tools included in the Java SE Development Kit

Eclipse is a cross-platform integrated development environment, mainly an IDE developed for Java applications and Android, with a large number of customized interfaces and countless plug-ins. Eclipse does not need to be installed, just unzip it to the directory file you want to install. If there is no ready-made IDE (Integrated Development Environment, integrated development environment, mainly refers to the application software that can assist in the development of programs), you can directly download the complete SDK package. Eclipse is included in the complete package, so there is no need to download and install it separately.

Android SDK is an Android application software development kit tool, which provides the API library required to develop Android applications and the development tools required to build, test and debug Android applications.

ADT (Android Developer Tools, Android Developer Tools), is a plug-in for Android application development on the Eclipse integrated development environment. This plug-in is actually a software tool used to develop Android applications on Eclipse. It can associate Eclipse with Android SDK, which is convenient for developers to develop and debug Android applications. The main development environment of the present invention is Eclipse 3.5.2, and the basic structure of the Android platform is as shown in Figure 3.

Configure the map module Android SDK, Figure 4 shows the main project directory of Android. Among them, the src folder is used to store the java program source code, and the assets folder is used to store the files packaged into the application as they are. The folder gen is used to store the source files generated by Android development tools, and there is an R.java file under it that is automatically generated and maintained by the development tools, and we do not need to create and modify it. When it is necessary to add reference files to the res directory, R.java can automatically complete the addition of references. At the same time, R.java can also judge whether all the files in the res directory are used when the program is compiled, and the unused files will not be packaged into the application program, which optimizes the execution space. The first few files in the res directory store image files with different pixels according to the file name, and layout and values store user interface files and text used on the interface respectively. AndroidManifest.xml is a function manifest file, where you can see how many activities, services, providers, receivers, and the required security authorization uses-permission in the entire project. After creating a libs folder in the project that has completed the configuration of the Android development environment, copy the files in the development package to the libs directory and integrate it into your own project.

To display Baidu Maps, you first need to add information such as the development key and required permissions to the AndroidManifest. Generally, the permissions required are mainly operator information, network positioning, GPS positioning, Wi-Fi network information, Wi-Fi access permissions and adding map controls in the layout xml file. As shown in accompanying drawing 5, accompanying drawing 6.

The display function in Android is one of the four major components—Activity. Activity is one of the most basic components in Android, which provides an interactive interface with users. A life cycle of an Activity refers to its state from creation to shutdown. In the whole process, there may be four states of operation, state, state and destruction, as shown in Figure 7.

When the Activity starts for the first time, the onCreate() method will be used to initialize the Activity, which is the beginning of an Activity life cycle. When opening the application, you need to run the three methods onCreateO, onStartO, and onResume() in order. At this time, the Activity has been displayed normally. If you click the back button at this time and call the three methods onPauseO, onStopO, and onDestory() successively, the application will end; if you press the Home button at this time to open other applications, the application will not end or be destroyed. , but executes the two methods onPause() and onStop() successively, and turns into a stop state. If the application is opened again, the three methods onRestartO, onStartO, and onResume() will be run in order to become running.

Baidu Maps must initialize the Context global variable referenced by the SDK when the application is created, and use the SDKInitializer.initialize(getApplicationContext()) method before calling each functional component of the SDK. To create a map Activity and manage the map life cycle, it is necessary to obtain the introduction of the map control through mMapView=(MapView)findViewById(R.id.bmapView) when opening. For the three states of pause, stop, and destruction, Baidu Maps provides three methods, mMapView.onPause(), mMapView.onResume(), and mMapView.onDestroy(), to realize map lifecycle management. Finally, use import to introduce related classes, as shown in Figure 8. So far, the entire development environment has been fully configured.

Step 2, based on the Activity application program on the mobile terminal of the Android system, design the detection mechanism structure and realize the main interface module;

Considering the functional requirements of the entire detection mechanism, we subdivide the entire detection mechanism into modules. We organize the logical structure into separate, functionally related discrete layers, cohesive in the main aspects, and make the logical structure more explicit. The logical structure of the entire detection mechanism can be divided into three layers: presentation layer, logic processing layer and data storage layer, as shown in Figure 9.

Presentation layer: Provide the message sender's software interaction page, including software setting page, message sending page and map display page.

Logic processing layer: Responsible for all data processing and data transmission of the entire detection mechanism of the system. Including the processing of parameter modification, the calculation of the distance between the message sender and the distance measuring point, the processing of the location of the message sender, and the judgment of the message credibility.

Data storage layer: mainly realizes the reception and storage of information reported by information reporters.

The data storage layer is mainly on the server side. Among them, the message ID and the reporter ID are both integer types, which are assigned in sequence by the system when obtaining messages and registering users. The message sending time is of DATETIME type, and the server date and time when the message is sent are obtained and recorded. The place where the message occurs and the content of the message are characters. Considering that the news generally reported will not exceed the maximum character limit of 8000 characters, so the text data is not stored in order to save storage space. There are only two situations for credibility judgment—the news is suspicious and the news is more reliable, so Boolean data can be expressed. The default message reliability is FALSE unreliable.

Table 3 data storage table

This detection mechanism is designed and implemented on the mobile terminal of the Android system. The Android application program is the entry file of all programs, but in fact the application program is only a broad concept, and there is no actual interface corresponding to it. In an application program, Activity represents a corresponding interface. An extension of Activity is equivalent to an interface. Most applications generally have multiple interfaces, and accordingly, the program will include multiple Activity classes. Therefore, from the perspective of actual display, the MainActivity.java file is the main interface of the program.

The main interface of the present invention mainly completes two functions, one of which is to complete the setting of three measuring points and the application setting for the delineation of the acceptable range, and the other is to complete the sending of instant information. Figure 11 shows the main interface of the program.

Regarding the settings of the three measurement points, we selected them through the coordinate system picked up by Baidu Maps. The Baidu map picking coordinate system is a geographic location information (presented in longitude and latitude coordinates) launched by Baidu that allows users to easily obtain the precise location of a certain location on the Baidu map, as shown in Figure 12.

Enter the place you want to search in the search bar and click Search, and the corresponding mark will appear on the map. Click on one of the marked points to see the corresponding coordinates; at the same time, all the searched places are listed on the right side of the page. places and their coordinates. If you don’t know the name of the specific location, put the mouse on the map and slide the mouse to each place, the corresponding map coordinates will be displayed synchronously, click on the selected coordinates, and the selected coordinates will be recorded in the upper right corner for future use for later use.

At the same time, the Baidu map pick-up coordinate system also provides the function of coordinate reverse check. When this function is selected, enter the coordinates of a known point in the search bar, and the point will be displayed on the map. If the coordinates are resolved successfully, an address can also be returned.

The formula for calculating the distance between two points on the map is shown in formula (1), where R=6370996.81, lng (Longitude) is the longitude, and lat (Latitude) is the latitude.

Because this experiment is mainly carried out in Wuhan City, Hubei Province, and at the same time, due to the fact that "a slight difference is a thousand miles away" on the map, the measurement points around the selected school are too close in data to be easy to distinguish from the data, so the present invention randomizes them on the surrounding map Three measurement points (114.349802, 30.535147), (114.363457, 30.545038) and (114.404498, 30.511795) were selected on the above.

In the selection of the acceptable distance range, we used a commonly used formula for distance interpretation - "five clears and six unclear, seven empty and eight empty, one thousand meters depends on labor", and chose 500 meters. The meaning of this mantra is that people can tell their gender through the clothes they wear and their body movements when the distance is 500 meters, but when the distance increases to 600 meters, they can't tell the difference between men and women; when the distance is 700 meters, they can see each other walking When walking between the two legs, you can’t see the space when walking at 800 meters; when the distance is 1000 meters, you can only see the relatively large movement changes such as sitting, standing, and bending over for labor. At that time, the human body is just a small black spot, and nothing can be distinguished. In order to refine the detection of real-time information, we choose 500 meters as the acceptable distance range where we can see normal behavior and distinguish body shape and gender.

All the above default data can be modified in the application settings as shown in Figure 12. In the selection of the three measurement points, as long as the distance between the two points is more than 100 meters (to avoid the existence of invalid measurement points), then if the message sender is within the triangle formed by the three selected measurement points, the measurement The effect will be even more. If the acceptable distance range for visually visible instant information is different, it can also be filled in by itself, but the present invention still recommends that 500 meters is relatively accurate. The default data is set and modified successfully, as shown in Figure 14. At the same time, if you are not satisfied with the set data and want to restore to the initial settings, you can also choose to restore the default coordinates, and the restoration is successful, as shown in Figure 15.

Step 3, based on the push information detection mechanism of the three-point positioning method, realize the detection of push information,

Step 3.1, locate the user who opens the application program, and obtain location information. When the user opens the app, we position the user, which is used to calculate the distance of the measurement point to draw the circle. Since the location of a person is constantly changing, we need to set a location change condition through the requestLocationUpdates() object. This condition includes the minimum time interval when the positioning request is initiated, and the minimum displacement change when the positioning request is initiated. These two conditions must be met at the same time to execute the callback function and trigger the location monitoring. In this way, we can avoid useless positioning repeated many times. Note that since we're asking for constant location updates, we'll have to do removeUpdates() manually. We only track when the Activity is running, otherwise the app will continue to update location information even if all activities in the app are closed. This will result in application resources not being reclaimed. Therefore, we continue to track in onResume(), and correspondingly turn off tracking in onPause().

Step 3.2, when the user sends a message, determine whether the message is empty, and at the same time query the location of the message to avoid sending blank and invalid information, as shown in Figure 16. When you use Baidu Maps to query addresses on a daily basis, there will often be multiple query results. In order to avoid the diversity of query results when querying the location of the message, the present invention selects the first result in the query results as the location of the message by default. Therefore, if you want to ensure the accuracy of the message address, when sending the message, the more detailed the address is, the closer the query result will be to the target address.

Step 3.3, calculate the distance of the measuring point, and draw a circle. Baidu Maps currently provides a circle drawing API class Circle(center:Point,radius:Number[,opts:CircleOptions]) to create a circle overlay, as long as the latitude and longitude of the center of the circle and the radius of the circle are passed in, the circle can be drawn. A new circle can be added through map.addOverlay(circle), and methods such as circle.setFillColor() and circle.setStrokeColor() are also provided to personalize the drawn graphics.

Step 3.4, information detection, based on the geometric scanning algorithm, proposes and adopts an algorithm for calculating the distance between the place where the reported message occurs and the area where the message sender is located.

The difficulty of the present invention mainly lies in how to judge whether the area where the message sender is located and the place where the reported message occurs are within an acceptable range. The calculated area where the message sender is located must exist. This area is formed by the intersection of three circles, and there may be four situations as shown in Figure 17. Figure 18 can be obtained by completing the area shown in Figure 17. The blackened part shows the intersection area of the design before completion. It can be seen that Figures 17a, 17b, and 17c correspond to Figures 18a, 18b, and 18c, respectively, and Figure 17d corresponds to Figures 18d and 18e. The three situations in Figure 18a, 18b, and 18d are actually attributed to the situation in Figure 18a, and the situation in Figure 18c actually has no common intersecting area for the three circles, which is different from the "calculated message" we obtained before The area where the sender is located must exist" is obviously different, so this situation does not fall into the scope of the present invention. Therefore, only the two cases of Fig. 18a and Fig. 18e need to be discussed in the present invention. Since the common areas shown in the two cases a) and e) in Figure 18 are not standard polygons, there is no direct processing method, so we need to approximate these areas. From Figure 19, we can see that the area where the three circles intersect is within the rectangle delimited by the four straight lines L1, L2, L3, and L4 in the figure, where L1 is the leftmost point of the three circles respectively The tangent of the circle based on the point closest to the right, L2 is the tangent of the circle based on the point closest to the left among the rightmost points of the three circles respectively, L3 is the tangent of the circle of the three circles respectively The tangent line of the circle based on the point closest to the uppermost point among the lowermost points, L4 is the tangent line of the circle based on the point closest to the lower point among the uppermost points of the three circles respectively. These four tangents exactly encompass the area where the three circles intersect. Again, this situation is also true for Figure 18e, so we use this rectangle to narrow down what we need to look for.

Considering that this algorithm is mainly researched on the points in the two-dimensional space of the map, the present invention refers to a similar algorithm—geometric scanning algorithm. In geometric algorithms, the main objects considered are usually points, line segments, polygons and other geometric objects in two-dimensional, three-dimensional or higher-dimensional spaces. Sometimes the solution to a problem requires "scanning" given input objects to gather information in order to find feasible solutions. This technique is called planar scanning on a two-dimensional plane, and space scanning on a three-dimensional space. In its simple form, a vertical line sweeps across the plane from left to right, stopping at each object (say, a point), starting with the leftmost object and sweeping right to the last measured object. object.

For example, in a set S with n points given on the plane, find the maximum point in the set. You can first arrange all the points in S according to their x coordinates in non-ascending order (if two points have the same x coordinate, then the point with the larger y coordinate value will be arranged in front), then the rightmost point Undoubtedly a maximal point, since it has the largest x-coordinate value. According to the geometric scanning algorithm, these points are scanned from the far right to the left, and at the same time, it is determined whether the y coordinate of these points is a maximum value. The whole algorithm process is shown in Figure 20, the maximal set {a, b, c, d, e} forms a ladder shape.

Based on the above geometric scanning algorithm, the present invention proposes the following algorithm to calculate the distance between the place where the report message occurs and the area where the message sender is located.

The process of the algorithm is shown in Figure 21. The scan line starts from the x-coordinate value of PL and scans to the right to scan all points whose y-coordinate value is between the y-coordinate value of PD and PU to the tangent line of the x-coordinate value of PR, and judge whether the point is within the range of three circles intersecting Inside. For each point within the intersecting range of the three circles under the x coordinate, calculate the distance between the two points with the largest and smallest y coordinate values and the place where the message occurred, record the minimum distance and continue to scan until the entire After the scanning process is over, the minimum distance obtained at last is the distance between the place where the news is reported and the area where the message sender is located. There are three situations for where the message occurs: above L4; below L3; between L3 and L4. According to different situations, for the same x value, the y value we need to scan is shown in formula (2).

When PD·y<P·y<PU.y, the y value direction needs to scan upwards from PD.y to the first point y1 within the intersection range, and then scan downwards from PU.y to the first A point y2 within the intersection range.

(1) If P.y≥y2, then the shortest distance is the distance between y2 and P;

(2) If P.y<y1, then the shortest distance is the distance between y1 and P;

(3) If y1≤P.y<y2, then the shortest distance is the distance between point (x, P.y) and P.

The three circles shown on the map are drawn according to the coordinates of the three measurement points and the distance from the sender of the message. Click "Scout Point 1", "Scout Point 2" and "Scout Point 3" to locate them respectively to the corresponding locations on the map of the three measurement points. Figure 22 shows the test results of sending messages about the Faculty of Arts and Sciences of Wuhan University in the Faculty of Informatics of Wuhan University.

The specific embodiments described in the present invention are only to illustrate the spirit of the present invention. Those skilled in the art to which the present invention belongs can make various modifications or supplements to the described specific embodiments or adopt similar methods to replace them, but they will not deviate from the spirit of the present invention or go beyond the definition of the appended claims range.

Claims (3)

1. a kind of push information based on three-point positioning method is characterized in that, comprises the following steps: Step 1, build the Android system development environment, specifically: Configure the Android development environment: install JDK and configure the variable environment of JDK on Windows, then download Eclipse and configure environment variables, then download and install the Android SDK, and finally install the ADT plug-in for Eclipse Map module Android SDK: Create a libs folder in the project, copy the files in the development kit to the libs directory and integrate it into your own project; Step 2, based on the Activity application program on the mobile terminal of the Android system, design the detection mechanism structure and realize the main interface module. The logical structure of the entire detection mechanism can be divided into three layers: the presentation layer, the logic processing layer and the data storage layer. Presentation layer: Provide software interaction pages for message senders, including software setting pages, message sending pages, and map display pages; Logic processing layer: Responsible for all data processing and data transmission of the entire detection mechanism of the system; including the processing of parameter modification, the calculation of the distance between the message sender and the distance measuring point, the processing of the location of the message sender, and the judgment of message credibility; Data storage layer: mainly realizes the reception and storage of information reported by information reporters; Step 3, based on the push information detection mechanism of the three-point positioning method, realize the detection of push information, Step 3.1, locate the user who opened the application, and obtain the location information, that is, set a location change condition through the requestLocationUpdates() object; this condition includes the minimum time interval when the location request is initiated, and the minimum displacement change when the location request is initiated; this The two conditions must be met at the same time to execute the callback function and trigger location monitoring; avoid repeated useless positioning; manually perform removeUpdates() to update the location information, continue tracking in onResume(), and close it in onPause() accordingly track; Step 3.2, when the user sends a message, judge whether the message is empty, and at the same time query the location of the message to avoid sending blank information and invalid information; Step 3.3, the three-point positioning method calculates the distance of the measuring point, and draws a circle; Step 3.4, information detection, based on the geometric scanning algorithm, proposes and adopts an algorithm for calculating the distance between the place where the reported message occurs and the area where the message sender is located. 2. according to claim 1, based on the push information detection method of three-point positioning method, it is characterized in that: the implementation mode of step 3.3 is, use Baidu map to draw circle API class Circle to create circle covering, by map.addOverlay( circle) can add a circle, and other methods to personalize the drawn graphics. 3. according to the described push information detection method based on the three-point positioning method of claim 1, it is characterized in that: the implementation mode of step 3.4 is, according to the geometric scanning algorithm, the point of the address space is studied, and the present invention proposes a The algorithm for calculating the distance between the place where the news is reported and the area where the reporter is located, input the three reconnaissance points S1, S2, S3 and the distances L1, L2, L3 between them and the message sender, and the place where the news happened P, then Get the distance L between the place where the news happened and the area where the news reporter is located.