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ENVIPseudoRasterSpatialRef::ConvertMapToFile

ENVIPseudoRasterSpatialRef::ConvertMapToFile

The ConvertMapToFile method converts the following within one pseudo spatial reference:

  • Geographic coordinates (x=longitude, y=latitude) to file (pixel) x,y coordinates
  • Projected coordinates (x=eastings, y=northings) in linear units to file (pixel) x,y coordinates

Pseudo map information refers to a non-standard projection that involves an affine map transformation. When an image is not georeferenced to a standard map projection and you only know the geographic coordinates and map projection of four points in the image, you can define these tie points in an ENVI header file or in the metadata of the raster object. ENVI will use these points to warp the image and to calculate geographic coordinates for each pixel. The pixel size varies in the rectified image. This type of projection contains a high degree of variability and is not geographically accurate; the (x,y) locations in the rectified image are only best guesses.

Example


See the example for ENVIStandardRasterSpatialRef::ConvertMapToFile. That example is for a standard spatial reference, but it works similarly for pseudo spatial references.

Syntax


ENVIPseudoRasterSpatialRef.ConvertMapToFile, MapX, MapY, FileX, FileY

Arguments


MapX

For a projected coordinate system, specify the x-coordinate (easting) in meters or feet. You can specify a scalar or a vector of MapX values; if it is a vector, the MapY argument should also be a vector with the same number of elements:

MapX = [481874.4000D, 482260.8000D]
MapY = [4428160.8000D, 4427992.8000D]

For a geographic coordinate system, specify the x-coordinate (longitude) in decimal degrees. You can specify a scalar or a vector of MapX values; if it is a vector, the MapY argument should also be a vector with the same number of elements:

MapX = [-112.0D, -83.0D]
MayY = [-39.0D, -37.0D]

MapY

For a projected coordinate system, specify the y-coordinate (northing) in meters or feet. For a geographic coordinate system, specify the y-coordinate (latitude) in decimal degrees.

FileX

A named variable that contains the pixel x-coordinate

FileY

A named variable that contains the pixel y-coordinate

Keywords


ERROR

Set this keyword to a named variable that will contain any error message issued during execution of this routine. If no error occurs, the ERROR variable will be set to a null string (''). If an error occurs and the routine is a function, then the function result will be undefined.

When this keyword is not set and an error occurs, ENVI returns to the caller and execution halts. In this case, the error message is contained within !ERROR_STATE and can be caught using IDL's CATCH routine. See IDL Help for more information on !ERROR_STATE and CATCH.

See Manage Errors for more information on error handling in ENVI programming.

Version History


ENVI 5.1

Introduced

API Version


3.2

See Also


ENVIPseudoRasterSpatialRef, ENVIRPCRasterSpatialRef::ConvertMapToFile, ENVIStandardRasterSpatialRef::ConvertMapToFile



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