Acronym for rational polynomial coefficients. In remote sensing and photogrammetry, typically 3rd 5th order polynomials that are used in ratios to provide a ground-to-image transformation. RPCs are generated from physical sensor models and can be accurate to subpixel levels, provided that the input to the generator software is accurate to that granularity. They are stable for long focal length, narrow field of view sensors, such as space-borne sensors. Because they lack a covariance model, RPCs are not considered to be full replacement sensor models.