What Is GeoTIFF?

A GeoTIFF is a TIFF raster file that carries the georeferencing information needed to place its pixels in geographic or projected space.

Ordinary TIFF describes an image, while GeoTIFF adds standardised tags that can identify the coordinate reference system and relate image rows and columns to real-world coordinates.

That makes GeoTIFF a common format for satellite imagery, aerial photography, digital elevation models, classified rasters, analysis outputs, and scanned maps that have been georeferenced.

A raster plus a spatial reference

A raster is a grid of cells, and without georeferencing, row 400 and column 900 identify a location only inside the image.

GeoTIFF metadata can define the transformation between that raster grid and a map coordinate system. Software can then place the image alongside vector boundaries, other rasters, and basemaps.

The OGC GeoTIFF 1.1 standard formalises tags for this cartographic information while relying on the underlying TIFF format for image structure, compression, colour interpretation, and other raster properties.

GeoTIFF does not describe one kind of raster value

The format can hold many types of raster data: a three-band GeoTIFF may contain red, green, and blue image values; a single-band file can contain elevation, temperature, land-cover class, probability, or another measured or derived quantity; and multi-band remote-sensing imagery can store many spectral channels.

The meaning of pixel values therefore comes from metadata and the dataset's domain—not from the .tif extension alone.

CRS metadata matters

A GeoTIFF can identify a coordinate reference system through GeoTIFF keys aligned with the EPSG register or through user-defined definitions.

If that metadata is missing or incorrectly written, however, the raster can still contain valid pixel values but fail to align geographically.

As with vector data, assigning the wrong CRS is not the same as reprojecting the raster correctly. Reprojection resamples the grid into a new coordinate space and can change pixel values depending on the resampling method.

Tiling and compression are TIFF concerns too

TIFF supports internal organisation choices such as strips or tiles and several compression methods. Those choices affect file size and access patterns without changing the fundamental geographic meaning of the raster.

A very large GeoTIFF can therefore be technically valid yet inconvenient to access over the web if a client must download most of the file before reaching a small region.

That problem motivated Cloud Optimized GeoTIFF.

GeoTIFF versus Cloud Optimized GeoTIFF

A COG is still a GeoTIFF/TIFF file, but its internal layout and remote-serving requirements are designed so clients can request only the byte ranges needed for a particular region and resolution. Not every GeoTIFF is therefore a COG: a file becomes cloud-optimised only when it follows the relevant tiling, overview, layout, and HTTP range-access requirements.

GeoTIFF vs Cloud-Optimized GeoTIFF explains that difference in detail.

GeoTIFF is usually an analytical raster, not a web map tile pyramid

It is useful to distinguish a georeferenced raster dataset from a rendered map-tile service.

A GeoTIFF can preserve numeric cell values for analysis, whereas raster web tiles are usually pre-rendered images partitioned by zoom and tile coordinate for display.

A COG can bridge some of that gap by allowing efficient remote access to the source raster, but the conceptual difference remains: one is a geospatial raster dataset; the other is a publication/delivery structure.

References

OGC GeoTIFF Standard. Defines the use of TIFF tags for georeferenced and geocoded raster imagery.
OGC GeoTIFF 1.1. Approved specification for GeoTIFF metadata and CRS referencing.