GeoTIFF

GeoTIFF is the most widely used raster file format for geospatial data. It extends the standard TIFF (Tagged Image File Format) specification by embedding geospatial metadata — coordinate reference system definitions, map projections, and spatial extents — directly within the file's existing tag structure. This means any software that can read a TIFF can still open a GeoTIFF as an ordinary image, while GIS-aware software can additionally interpret the geographic context. Standardized by the Open Geospatial Consortium (OGC) as OGC GeoTIFF (version 1.1), the format has become the de facto interchange standard for satellite imagery, digital elevation models, orthophotos, and virtually any raster dataset that needs to be georeferenced.

GeoTIFF uses the extensible tag architecture of TIFF 6.0 to store geolocation metadata without introducing proprietary structures. The core mechanism uses a compact system of "GeoKeys" — small metadata entries encoded within a few reserved TIFF tags. The primary tag is the GeoKeyDirectoryTag (Tag ID 34735), an array of unsigned short integers that define a directory of all GeoKeys present in the file. Supplementary tags include GeoDoubleParamsTag for floating-point values and GeoAsciiParamsTag for string parameters. Together, these tags can encode projection type, coordinate reference system, datum, ellipsoid, units, and transformation parameters.

A GeoTIFF can use one of three model types: geographic (latitude/longitude), projected (e.g., UTM), or geocentric. Spatial positioning is defined via ModelTiepointTag (mapping raster coordinates to ground coordinates) and ModelPixelScaleTag (defining ground distance per pixel), or alternatively via a full affine transformation matrix for rotated or skewed imagery.

As a flat-file format, a single GeoTIFF has no built-in support for time series or multi-temporal stacks — each time step requires a separate file. The format does not natively support complex data structures such as irregular grids, vector geometries, or hierarchical groups (unlike NetCDF or HDF5). Very large files can be slow to access over networks because a standard GeoTIFF may require reading large contiguous blocks — a limitation that led to the development of Cloud Optimized GeoTIFF (COG). Metadata beyond coordinate reference information must be stored in non-standardized TIFF tags or external sidecar files. The TIFF specification's 4 GB file size limit applies to classic GeoTIFF, though BigTIFF extends this.

GeoTIFF originated in the early 1990s as an effort to standardize how geospatial metadata was embedded in raster files. Dr. Niles Ritter and Mike Ruth, working initially at the Jet Propulsion Laboratory (JPL), led the development. Version 1.0 was published in 1995 through collaboration between NASA/JPL, USGS, and the geospatial software community. The specification was designed to be backward-compatible with TIFF 6.0. Adoption was rapid: by the late 1990s, GeoTIFF had become the standard output format for most remote sensing and GIS software. In 2019, the Open Geospatial Consortium formalized GeoTIFF as OGC standard 19-008r4 (GeoTIFF 1.1). Today, GeoTIFF is supported by virtually every geospatial tool, from GDAL and Rasterio to ArcGIS and ENVI.