Generally, geoTIFF files containing RGB/RGBA or elevation data contain a header which describe the coordinate system which the file content data is georeferenced in. For many files that are in a local or arbitrarily defined coordinate system, however; the geoTIFF header does not contain the complete coordinate system definition — and may only contain a string such as "LOCAL CS". Therefore we require a supplementary definition in order to correctly process these files.
If a site has been set up with a local site calibration, it is possible to upload local GeoTIFF files for processing through the Create new dataset flow, choosing the Pre-processed data option.
In the Choose files to upload screen as below, tick "This file is in the site's local system" for each file to which it applies.
Note that this option will not be shown if the selected Site does not have a local calibration.
Ticking this option tells us that we should use the Site coordinate system definition (local calibration) instead of the TIFF file's header — which is likely to define only the system's underlying projection (without the affine / geoid adjustments in xy and z).
How to know that your file is in a local system
- If you know that your file is in a system which includes a shift in XY and/or Z from the underlying projection
- If you use a software that requires that you define a coordinate system (such as a DC/CAL/JXL file in Trimble products, or a GC3 file in Topcon products)
- More technically — if the file system cannot be defined by a WKT string or PRJ file.