GeoTIFF defines a set of Tagged Image File Format (TIFF) tags, which describe
cartographic and geodetic information associated with geographic TIFF imagery.
GeoTIFF is a means for tying a raster image to a known model space or map projection
and for describing those projections. A metadata format provides geographic
information to associate with the image data. However, the TIFF file structure allows
both the metadata and the image data to encode into the same file.
The description of an image in GeoTIFF requires tags and keys; the image files contain
these tags and keys, which are read by GeoTIFF readers.
GeoTIFF tags convey information about the image. The tags describe the image using
information the GeoTIFF reader needs to control the appearance of the image on the
user’s screen. The TIFF tags are embedded in the same file as the TIFF image. The
GeoTIFF tags provide information on the image projection and corner points, which
define the geographic location and extent of the image.
A complete description of the raster data requires geo-referencing of the data, which is
accomplished using tags.