Custom Query (95 matches)

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.

Currently the calibrate adjusts for the offset then multiplies by the scale factor, which works for a stretched tape with the end missing *calibrate tape 0.05 0.752

But of things like mounting a DistoX in a waterproof case the offset will be measured with another device so will not want scaling

Suggestion is to allow the addition of units to the offset if the scale factor should not be applied, this should allow the original format to continue to work while adding functionality.

if not units

real = ( reading - offset) * scale

If units eg *calibrate tape -0.05m 0.752

real = reading * scale - offset

If you use aven to export a GPX file and just tick 'entrances', then the resulting file has a </gpx> at the end, but does not have a <gpx> tag at the start. Programs will refuse to import it as invalid (QGIS and viking tested).