Centimetre accurate and free EOV transformation

Abstract

Most geospatial software uses the open-source PROJ for transformation between different map projections. For a long time, to calculate Hungarian EOV coordinates of the national map projection, the necessary transformation between the Hungarian Datum 1972 (HD72) and the European Terrestrial Reference System 1989 could have been completed using a single parameter set of similarity transformation, which can be characterized by pure, decimetre accuracy. Centimetre-accurate transformation is achievable by applying the VITEL 2014 procedure and their grid shift files; however, VITEL 2014 is not freely available. In 2014, we developed and published our VITEL-like, PROJ-compatible grid shift files, having practically the same results. Over the recent months, we made some minor and formal updates to our grid shift files. After completing the necessary administrative procedures, our files were published in the PROJ-data repository with a CC-BY licence.  GIS software applying PROJ v9.5.1 and the PROJ-data v1.20 or higher, like QGIS 3.40.3, computes Hungarian EOV coordinates with centimetre-accurate datum transformation.