Implementing GeoKeys (GeoTIFF tags)

GeoTIFF files support standard TIFF comments and tags, but also contain six additional data tags describing the image location, scale, projection, and other information useful for topographic applications. Use the following functions to work with GeoKeys:

To read a particular GeoKey from a file, call L_ReadFileGeoKey.
To read all the TIFF GeoKeys from a file, call L_ReadFileGeoKeys.
To determine whether the given file format supports TIFF GeoKey tags, call L_GeoKeysSupported.
To enumerate the GeoKeys from an existing file, call L_EnumFileGeoKeys. For each GeoKey enumerated, ENUMGEOKEYSCALLBACK is called.
To set GeoKeys in preparation for writing or saving, use L_SetGeoKey. These GeoKeys are maintained as a per-thread array. Call L_GetGeoKey to obtain the list of GeoKeys that have been set.
To free the data allocated by calling the L_ReadFileGeoKeys function, call L_FreeFileTags.
Write GeoKeys in one of two ways:
1. Save a new image as FILE_GEOTIFF with a save function, such as: L_SaveFile or L_SaveBitmap.
2. Update an existing file using L_WriteFileGeoKey or L_WriteFileMetaData.

There are 65536 possible GeoKey values. The GeoTIFF specification recommends the following ranges (domains) for GeoTIFF data:

Range	Description
0..1023	Do not use: reserved for future use.
1024..2047	GeoTIFF configuration keys.
2048..3071	Geographic/Geocentric CS Parameter Keys.
3072..4095	Projected CS Parameter Keys.
4096..5119	Vertical CS Parameter keys.
5120..32767	Reserved.
32768..65535	Private: use to store your own data.

Note: To save a region inside a TIFF file, you must have an unlocked Document or Medical Imaging license.

For more information about GeoTIFF tags, Predefined GeoKey values, and GeoTIFF Specifications, refer to https://trac.osgeo.org/geotiff/

Implementing GeoKeys (GeoTIFF tags)

See Also