Orthorectification of prisma images

Orthorectification is one of the most important satellite imagery pre-processing applications, as it allows to use data, for example, in geographic information systems, making the most of high or medium resolution. Since May 2020, PRISMA (PRecursore IperSpettrale della Missione Applicativa) mission, a project of the Italian Space Agency, has become fully accessible to the community. PRISMA satellite integrates a hyperspectral sensor and a medium-resolution panchromatic sensor. The products are currently available with a declared geolocation accuracy of 200 m, which ASI plans to increase to half pixel in the near future by introducing geometric treatment of the images with Ground Control Points (GCPs). However, the orthorectification of PRISMA images is not a proven and validated procedure, due to the uncertainty of satellite orbital and internal orientation data provided in the metadata file and to the lack of contributions on the subject in literature. In the present work, our contribution on possible strategies for the geometric treatment of PRISMA images is shown. The results obtained by applying the Rational Polynomial Coefficients (RPC) provided with some panchromatic images show coarse rototranslations. For this reason, a procedure was developed to restore conformity between RPCs and the panchromatic image. The best results in terms of accuracy were obtained with the rational polynomials using RPF approach, achieving residuals calculated on the Check Points (CP) in the order of one pixel, better than those supposed by ASI using GCPs. Probably even better results could be obtained with more rigorous information on RPCs or orbital and orientation parameters.