DSPNT2D - Interpolate at a single point (or points) in 2D in double precision

       To use DSPNT2D, load the NCAR Graphics library ngmath.

       Copyright (C) 2000
       University Corporation for Atmospheric Research

       The use of this Software is governed by a License Agreement.

UNIX                                           September 1997-1998                               DSPNT2D(3NCARG)

       N           (Integer, Input) - The number of input data points.

       X           (Double precision, Input) - An array containing the X coordinates of the input data points.

       Y           (Double precision, Input) - An array containing the Y coordinates of the input data points.

       Z           (Double  precision,  Input)  -  An  array  containing the functional values of the input data
                   points. That is, Z(L) is the value of the  input  function  at  coordinate  (X(L),Y(L)),  for
                   L=1,N.

       M           (Integer, Input) - The number of output data points (this may be "1").

       XO          (Double  precision,  Input)  -  An  array  of dimension M containing the X coordinates of the
                   output data. The values in XO may be in any order.

       YO          (Double precision, Input) - An array of dimension M  containing  the  Y  coordinates  of  the
                   output data. The values in YO may be in any order.

       ZO          (Double  precision,  Output)  -  An  array of dimension M containing the interpolated values.
                   ZO(I) is the interpolated value at point (XO(I),YO(I)) for I=1,M.

       IER         (Integer, Output) - An error return value. If IER is returned  as  0,  then  no  errors  were
                   detected. If IER is non-zero, then refer to the man page for dsgrid_errors for details.

       DSPNT2D - Interpolate at a single point (or points) in 2D in double precision

       dsgrid, dsgrid_params.

       Complete documentation for Dsgrid is available at URL
       http://ngwww.ucar.edu/ngdoc/ng/ngmath/dsgrid/dshome.html

       CALL DSPNT2D (N, X, Y, Z, M, XO, YO, ZO, IER)

       This subroutine is called when you want to interpolate at an individual point or points.