Planet supplies Rational Polynomial Coefficients (RPCs) for Pelican Basic imagery, consistent with SkySat and PlanetScope products.

RPCs provide a mathematical relationship that maps 3D ground coordinates (latitude, longitude, elevation) to 2D imagery coordinates (row, column pixels) and vice versa. This mapping enables accurate feature geolocation and removes geometric distortions caused by sensor geometry, terrain relief, and satellite attitude during acquisition.

How RPCs work

RPCs use polynomial ratios to approximate a physical sensor model, providing forward (ground to imagery) and inverse (imagery to ground) transformation coefficients derived during geometric processing.

Because RPCs represent an approximation of the rigorous physical sensor model Planet uses for Pelican orthorectified imagery products, user-generated orthorectified imagery may not match Planet-delivered orthorectified imagery exactly. RPCs are generated for individual tiles, which can introduce discontinuities at tile boundaries.

Working with Basic imagery

Planet delivers RPCs alongside Basic products for workflows requiring custom geometric correction:

• Uncorrected source data: Basic products are not orthorectified or terrain-corrected by Planet.

• Orthorectification requirements: You can apply geometric corrections using standard GIS tools alongside a Digital Elevation Model (DEM).

• Delivery format: For Pelican, RPCs are provided as text (.txt) files and embedded directly in the TIFF header of the Basic product.