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


The following example converts a set of lon/lat coordinates to map coordinates within the same spatial reference.

; Launch the application
; Open a file
file = FILEPATH('qb_boulder_msi', ROOT_DIR=e.ROOT_DIR, $
  SUBDIRECTORY = ['data'])
raster = e.OpenRaster(file)
spatialRef1 = raster.spatialRef
; Provide a set of lon/lat coordinates
Lon = -105.2212463D
Lat = 40D
spatialRef1.ConvertLonLatToMap, Lon, Lat, MapX, MapY
PRINT, 'Lon/Lat coordinates: ',Lon, Lat
PRINT, 'Map coordinates: ',MapX, MapY


ENVIStandardRasterSpatialRef.ConvertLonLatToMap, Lon, Lat, MapX, MapY



The longitude coordinate in meters or degrees. You can specify a scalar or a vector of longitude values; if it is a vector, the Lat argument should also be a vector with the same number of elements:

Lon = [-123.58, -134.64]
Lat = [48.23, 49.56]


The latitude coordinate in meters or degrees


A named variable that contains the map x-coordinate


A named variable that contains the map y-coordinate



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

ENVIStandardRasterSpatialRef, ENVIPseudoRasterSpatialRef::ConvertLonLatToMap, ENVIRPCRasterSpatialRef::ConvertLonLatToMap