Trust Refining Points (PRFs)

Representation of the points for which the coordinates have been identified during aerophotogrammetric return.In order to complete the GRP network, and to make the distribution of known points uniform, especially in high mountain areas (average altitude above 1 500 m) or heavily wooded, a number of photogrammetric refinement points (PRFs) have been established, determined by aerial triangulation or in any case by numerical return. They are made up of photographic details certainly identifiable on the ground and of appropriate finesse (bivi and crossroads, poles and masts, etc.). The PRFs are marked on the paper by a circle with wings.The representation is associated with the monographs of the dots in PDF format. Not all monographs contain numerical coordinates, but they are still reported in the database.