|Introduction | Sustainability Factors | Content Categories | Format Descriptions | Contact|
|Full name||GeoTIFF, Revision 1.0|
GeoTIFF is format extension for storing georeference and geocoding information in a TIFF 6.0 compliant raster file by tying a raster image to a known model space or map projection. A GeoTIFF file is a TIFF 6.0 [TIFF_6] file, and inherits the file structure as described in the corresponding portion of the TIFF spec. The GeoTIFF format uses a defined set of TIFF tags to describe cartographic information associated with TIFF imagery that originates from satellite imaging systems, scanned aerial photography, scanned maps, digital elevation models, or as a result of geographic analyses.
GeoTIFF can store a broad range of georeferencing information, catering to geographic as well as projected coordinate systems needs. Supported projections include UTM, US State Plane and National Grids, as well as the underlying projection types such as Transverse Mercator, Lambert Conformal Conic, etc. GeoTIFF uses a "MetaTag" (GeoKey) approach to encode dozens of information elements into just 6 tags, taking advantage of TIFF platform-independent data format representation to avoid cross-platform interchange difficulties.GeoTIFF uses numerical codes to describe projection types, coordinate systems, datums, ellipsoids, etc. In the Format Specification Revision 1.0, see Section 2.4. GeoTIFF File and Key Structure and the Appendices for Tag ID, KeyID and numerical code details.
Like TIFF format, GeoTIFF uses 32-bit offsets, thus limiting its extent to 4 gigabytes. The needs of GIS, large format scanners, medical imaging and other fields have prompted development of the variant BigTIFF format, which transcends the 4 GB TIFF limit using 64-bit offsets thereby supporting files up to 18,000 petabytes in size.
|Relationship to other formats|
|Subtype of||TIFF_6, TIFF, Revision 6.0|
|Has extension||BigTIFF, BigTIFF|
|LC experience or existing holdings||The Library of Congress has acquired cartographic images in GeoTIFF format for its collections, for example, the National Land Cover Dataset for 1992, acquired on CDs.|
|LC preference||For works acquired for its collections, the list of Library of Congress Recommended Formats Statement for Still Image works, as of February 2017, indicates that GeoTIFF is the preferred format for cartographic raster images.|
|Disclosure||GeoTIFF is an open, fully documented extension to Aldus-Adobe's public domain Tagged-Image File Format (TIFF), Revision 6.0|
|Documentation||Ritter, Niles and Mike Ruth, GeoTIFF Working Group. GeoTIFF Format Specification: GeoTIFF Revision 1.0, December 28, 2000. Note that the "specification version" is given as 1.8.2. As of late 2016, the official specification is a copy stored at the Internet Archive.|
GeoTIFF represents an effort by over 160 different remote sensing, GIS, cartographic, and surveying related companies and organizations to establish a TIFF based interchange format for georeferenced raster imagery.
GIS/Image processing packages which support GeoTIFF include: USGS's dlgv32, ESRI ARC/INFO, ESRI ArcExplorer, ESRI ArcView, ERDAS IMAGINE, PCI’s EASI/PACE, MAP INFO, GLobal Mapper, and Python Imaging Library.
USGS offers Digital Orthoquadrangle (DOQ) in GeoTIFF.
Spatial Data Transfer Standard (SDTS) allows a GeoTIFF image to be included with other files.
USGS National Map Seamless Server products in GeoTIFF format include: National Elevation Dataset (NED), National Land Cover Data (NLCD) data, Shuttle Radar Topography Mission (SRTM) data, Digital Orthophoto Quarter Quadrangle (DOQQ) data, Moderate Resolution Imaging Spectroradiometer (MODIS) Direct Broadcast (DB) US Normalized Difference Vegetation Index (NDVI) data, Land Processes Distributed Active Archive Center (LP DAAC) MODIS All Bands, and Landsat Mosaic Satellite imagery.
NASA's Oak Ridge National Laboratory Distributed Active Archive Center (ORNL DAAC) suggests GeoTIFF as a preferred image file format for archiving in its Best Practices for Preparing Environmental Data Sets to Share and Archive
A handout from the National Map indicates that the commercial version of Global Mapper software can convert the US Topo Quadrangle GeoPDF_2_2 files to GeoTIFF. All GeoPDF layers are flattened into a single raster image, with vector layers rasterized and combined with other raster layers. The resulting file can be printed, viewed online, or used as a background image within a GIS system.
|Licensing and patents||Portions of the GeoTIFF specification are copyrighted by Niles Ritter and Mike Ruth. Permission to copy without fee all or part of the specification material is granted provided that the copies are not made or distributed for direct or commercial advantage and the GeoTIFF specific copyright notice appears (see specification copyright notice). TIFF is a registered trademark of Aldus Corp., now owned by Adobe.|
|Self-documentation||See TIFF_6. All GeoTIFF specific information is encoded in several additional reserved TIFF tags, and contains no private Image File Directories (IFD's), binary structures or other private information invisible to standard TIFF readers. See also Tags for TIFF and Related Specifications.|
|External dependencies||Requires a TIFF reader that is able to parse the “Geokey” MetaTag values (mentioned in Description), as well as to reliably execute two general requirements of the TIFF standard: to manage byte order (big and little endian) and to support for all documented TIFF 6.0 tag data-types, and in particular requires the IEEE double-precision floating point "DOUBLE" type tag.|
|Technical protection considerations|
|Normal rendering||Good support. All GeoTIFF specific information is encoded in several additional reserved TIFF tags, and contains no private Image File Directories (IFD's), binary structures or other private information invisible to standard TIFF readers. In systems that don't read geography, but do read TIFF image format, a GeoTIFF image should look and behave like any other TIFF image.|
|Clarity (high image resolution)||
Excellent support for images with very high spatial resolution. The standard is flexible as to color space and bit depth. In practice, 8-bit grayscale and 24-bit RGB color are common; some activities create files with greater than 8 bits per channel (color or greyscale).
|Color maintenance||See TIFF_6|
|GIS images and datasets|
The role of a GeoTIFF in normal GIS use is often as a visual base layer. The GeoTIFF format provides enough information that the software can automatically place an image without requirement of any user intervention, such as typing in coordinates, digitizing points, or other labor intensive and technical actions.
Most GeoTIFF-savvy systems look at the geographic information and use it without any requirement that the user know the content of the geographic tags. One aim of GeoTIFF is to reduce the need of users to be geographic experts in order to load a map-projected image or scanned map.
GeoTIFF provides a robust framework for specifying a broad class of existing projected coordinate systems.
GeoTIFF requires support for all documented TIFF 6.0 tag data-types, and in particular requires the IEEE double-precision floating point "DOUBLE" type tag. Most of the parameters for georeferencing will not have sufficient accuracy with single-precision IEEE, nor with RATIONAL format storage.
|Support for GIS metadata||GeoTIFF uses a small set of reserved TIFF tags to store a broad range of georeferencing information, including: coordinate systems, datums, ellipsoids, and projections.
Projections include UTM, US State Plane and National Grids, as well as the underlying projection types such as Transverse Mercator, Lambert Conformal Conic, etc.
The projection, datums and ellipsoid codes are derived from the EPSG list compiled by the Petrotechnical Open Software Corporation (POSC), and mechanisms for adding further international projections, datums and ellipsoids has been established.
|Support for grids||GeoTIFF images can be transformed and displayed as pixel based GRIDs.|
|Beyond normal functionality||
GeoTIFF is fully extensible, permitting internal, private or proprietary information storage.
As with TIFF, in GeoTIFF private "GeoKeys" and codes may be used, starting with 32768 and above. Unlike the TIFF spec, however, in GeoTIFF these private key-spaces will not be reserved, and are only to be used for private, internal purposes since the GeoTIFF standard arose from the need to avoid multiple proprietary encoding systems, use of private keycode implementations is discouraged.
|All sample file examples in official archive at http://download.osgeo.org/geotiff/samples/ have .tif as extension.|
|Internet Media Type||image/tiff
||See also TIFF_6|
|Wikidata Title ID||Q1502796
GeoTIFF projection, datums and ellipsoid codes are derived from the European Petroleum Survey Group (EPSG) list compiled by the Petrotechnical Open Software Corporation (POSC), and mechanisms for adding further international projections, datums and ellipsoids have been established.
The GeoTIFF information content is designed to be compatible with the data decomposition approach used by the National Spatial Data Infrastructure (NSDI) of the U.S. Federal Geographic Data Committee (FGDC).
The GeoTIFF specification requires that TIFF-compliant readers honor the 'byte-order' indicator: this means that 4-byte integers from files created on opposite order machines must be swapped in software, and that 8-byte DOUBLE's must be 8-byte swapped.
GeoTIFF requires reliable support for the TIFF 6.0 "DOUBLE" data-type tag, pertaining to IEEE double-precision floating point data. Most of the parameters for georeferencing will not have sufficient accuracy with single-precision IEEE, nor with RATIONAL format storage. The only other alternative for storing high-precision values would be to encode as ASCII, but this does not conform to TIFF recommendations for data encoding.
In late 2016, the use of the remotesensing.org domain for the GeoTIFF specification and supporting documentation was terminated. The primary GeoTIFF website as of early 2017 is http://geotiff.osgeo.org, which redirects to https://trac.osgeo.org/geotiff/.
Discussion at NASA has led to some suggestions for refinements to the GeoTIFF specification. The compilers of this resource have not determined how actively these suggestions are being pursued. Comments welcome.