I am working on georeferencing of some old maps (before XIX century).
It seems that maps are based on `Bessel Datum Lisboa´ coordinate system but still I haven't found any software ore mathematical model to convert from this system to another one, available nowadays. So far I am trying to find ground control points (GCP,s) and to georeferenc those point to the reference map but this is not the mos accurate solution!
Looking forward for any possible solution!
Sincerely,
Hello Alban,
QGIS has a native "Lisboa_Bessel_Bonne" Datum (EPSG 102 163), did you already try it?
Also, you may download NTv2 grids and use them in QGIS. To convert from Bessel to ETRS89, among others, download grids here: http://www.fc.up.pt/pessoas/jagoncal/coordenadas/parte1.htm Other options here: http://www.dgterritorio.pt/cartografia_e_geodesia/geodesia/transformacao_de_coordenadas/grelhas_em_ntv2/
Explanation how to use them in QGIS here (in Portuguese, sorry, but find me at the university and I will help you translate): http://qgis.pt/blog/2014/07/13/transformacao-de-coordenadas-e-utilizacao-das-grelhas-ntv2-no-qgis/
Best regards,
André
Dear Alban,
Have you tried using R?
R does these datum conversions and, theoretically, any conversion in possible in R.
Best regards,
Rui
Dear André and Rui, many thanks for the significant information!
Rui do you have a relevant R script, if you have can you send to me?
Best regards,
Hey, I would suggest you to go with Python, it should be a script of a couple of lines.
https://publicwiki.deltares.nl/display/OET/Python+convert+coordinates
http://robotics.ai.uiuc.edu/~hyoon24/LatLongUTMconversion.py
Cheers
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