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  >  Docs Center  >  ENVI API  >  Data Control  >  ENVIPseudoRasterSpatialRef::ConvertMapToLonLat



The ConvertMapToLonLat method converts a set of map coordinates (x-eastings, y-northings) to a set of geographic latitude and longitude coordinates within one spatial reference. The associated ENVIRaster's metadata must include a coordinate system string.

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.


ENVIPseudoRasterSpatialRef.ConvertMapToLonLat, MapX, MapY, Lon, Lat



The map x-coordinate. 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]


The map y-coordinate


A named variable that contains the longitude value


A named variable that contains the latitude value



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


API Version


See Also

ENVIPseudoRasterSpatialRef, ENVIRPCRasterSpatialRef::ConvertMapToLonLat, ENVIStandardRasterSpatialRef::ConvertMapToLonLat

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