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Harris Geospatial / Docs Center / IDL Reference / I/O - EOS / EOS_GD_INTERPOLATE

EOS_GD_INTERPOLATE

EOS_GD_INTERPOLATE

This function performs bilinear interpolation on a grid field. It assumes that the pixel data values are uniformly spaced which is strictly true only for an infinitesimally small region of the globe but is a good approximation for a sufficiently small region. The default position of the pixel value is pixel center, however if the pixel registration has been set to 1 (with the EOS_GD_DEFPIXREG function) then the value is located at one of the four corners specified by the EOS_GD_DEFORIGIN routine.

All entries along the non-geographic dimensions (i.e., NOT XDim and YDim) are interpolated and all interpolated values are returned as FLOAT64. The reference for the interpolation algorithm is Numerical Recipes in C (2nd ed). (Note for the current version of this routine, the number type of the field to be interpolated is restricted to 22, 24, 5, 6.)

Examples


To interpolate the Spectra field at two geographic data points:

lonVal[0] = 134.2d
latVal[0] = -20.8d
lonVal[1] = 15.8d
latVal[1] = 84.6d
bufsiz = EOS_GD_INTERPOLATE(gridID, 2, lonVal, latVal, $
   "Spectra", interpVal)

Syntax


Result = EOS_GD_INTERPOLATE(gridID, Interp, lonVal, latVal, fieldname, interpVal)

Return Value


Returns size in bytes of interpolated data values if successful and FAIL(–1) otherwise.

Arguments


gridID

Grid id (long) returned by EOS_GD_CREATE or EOS_GD_ATTACH

nInterp

Number of interpolation points (long).

lonVal

Longitude of interpolation points (double array).

latVal

Latitude of interpolation points (double array).

fieldname

The field (string) from which to interpolate data values.

interpVal

A named variable that will contain the (double) interpolated data values.

Keywords


None

Version History


5.2

Introduced



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