! sp2 Geoff's brain production
!    Copyright (C) 1999,2010 Gauthier Delerce
!
!   This program is free software; you can redistribute it and/or modify
!   it under the terms of the GNU General Public License as published by
!   the Free Software Foundation; either version 2, or (at your option)
!   any later version.
!
!   This program is distributed in the hope that it will be useful,
!   but WITHOUT ANY WARRANTY; without even the implied warranty of
!   MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
!   GNU General Public License for more details.
!
!   You should have received a copy of the GNU General Public License
!   along with this program; if not, write to the Free Software Foundation,
!   Inc., 59 Temple Place - Suite 330, Boston, MA 02111-1307, USA.
!
! Gauthier Delerce <gauthier@delerce.fr>

!*-------------------------------------------------------------------------
!*	SP2 - solve for U at XI,YI given spline coefficients in S & T
!*	from SP1.  X and Y are coordinate arrays same as those sent to SP1.
!*-------------------------------------------------------------------------

	subroutine sp2(xi,yi,x,y,n,s,t,u)
	implicit real(8) (a-g,o-z)
	real x(n),y(n),xi,yi,u
	real(8) s(n),t(3)

	u=0.

!*------------ interpolate at Xi,Yi from S(N) coefficients ---------------

	do k=1,n
		dx=dble(xi-x(k))
		dy=dble(yi-y(k))
		tt=dx*dx+dy*dy
		if (tt.ne.0.d0) then
			dltt=dlog(tt)
			dxtt=dx*(dltt+1.d0)
			dytt=dy*(dltt+1.d0)
			u=u+sngl(s(k)*tt*dltt)
		endif
	end do

!*----------------- add the contribution from the Ts ----------------------

  	u=u+sngl(t(1)*xi+t(2)*yi+t(3))
	return
	end