[Therion] Survex Terrain model problem

Olly Betts olly at survex.com
Thu Mar 24 14:50:19 CET 2016


On Thu, Mar 24, 2016 at 03:36:04PM +0200, Владимир Георгиев wrote:
> Hmm, you seem to be talking about the original Survex data file. I see the
> format is similar to the .th files, but I meant producing a 3D file
> exported from Therion.
> 
> In the Therion data I have a CS command and a fixed station, but maybe this
> is not exported to the 3D file for consuming by Survex.

I suspect therion hasn't yet been updated to include coordinate system
information when it exports a .3d file.

It should be fairly easy to update - just call img_open_write_cs()
instead of img_open_write() and pass in the PROJ4 projection string for
the output coordinate system as an extra parameter.

> Most of the 3D file looks binary and I can't find out whether it
> contains this info or not.

You can see if you use the "dump3d" tool - it'll include a "CS" line in
the header section if the coordinate system is specified, e.g.:

CS +proj=utm +ellps=WGS84 +datum=WGS84 +units=m +zone=33 +no_defs

Or look for a string starting "+proj" near the start of the file itself.

But if aven says there's no coordinate system specified, it's just
checked that for you.

Cheers,
    Olly



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