TIFF is an open file format that is widely used for raster imagery and aerial photography. A GeoTIFF file is a georeferenced TIFF, which means it can have geographic information such as map projections embedded within the header file of the TIFF itself.
This means that a GIS application can position the image in the correct location, which makes it more useful than earlier file formats, such as GeoJPEG.
Strictly speaking, GeoTIFF is a metadata format, but the TIFF format enables both the data and metadata to exist in the same file.
Common uses for GeoTIFFs
GeoTIFFs are commonly used for a range of raster data, including:
- remote sensing & aerial photography;
- satellite data;
- grids; and,
- cartographic representations, such as georeferenced topomaps.
GeoTIFFs are also often supported by GPS units.
We export GeoTIFFs using LZW internal compression. These are tiled and pixel-interleaved. This allows for a lossless export, which means you can access your chosen data at full resolution.
As mentioned above, the projection information and other metadata for each GeoTIFF is included in the header file. However, because some older software applications are unable to process this header file, we include an additional .tfw file per GeoTIFF download. This provides coordinate information for each pixel, which enable GIS software to correctly process the file.
We support the import of both GeoTIFF rasters and grid data, and will automatically determine whether your data is grid or raster during the import process.
We support a range of compressed GeoTIFF types, as well as uncompressed GeoTIFF files.
NoData and Alpha
For most raster exports, we preserve any existing Alpha bands, and add an Alpha band to mark where data is and is not (noting that Alpha represents transparency). This means that most raster exports will be RGB(A).
There are two exceptions. First, exports of data that preserve the original projection can be RGB, if the source data did not contain an Alpha band. Second, grid layers do not support Alpha bands, so grid exports will get a NoData value instead.