id summary reporter owner description type status priority milestone component version resolution keywords cc 56 Sort out handling of geoid Olly Betts Olly Betts "Currently the altitude of GPS fixes and hence of cave entrances attached to them doesn't match the altitude of terrain from DEM files very well - the difference seems to be a few 10s of metres. Newer versions of proj have support for geoids, which should solve this: https://trac.osgeo.org/proj/wiki/VerticalDatums I think proj >= 4.8.0 is needed - the release announcement for it includes ""Added preliminary vertical datum support"". That was released 2012-03-14, so shouldn't be an unreasonable requirement. It would be good to coordinate how vertical datums are handled with therion, but they didn't respond to my email to their list about doing so." defect closed major 1.4.0 aven 1.2.18 fixed