[Therion] Projected Elevation Reprojection

[Bruce Mutton]

Hi Footleg

Generally I have found it is better to draw each scrap specifically for the projection it is intended for.  Hence PocketTopo sketches will usually be unsuitable for projected elevations, as PocketTopo is strictly ‘extended’ as far as elevations go.

However, you can use -flip horizontal in the scrap definition to swap them around, eg;

 

scrap 06-WhiteLimeElevEXT-s1 -projection extended -flip horizontal -author 2015.04.29 "B Mutton" -copyright 2015 NZSS -scale [0 0 393.7 393.7 0 0 10 10 m]

 

ie this was a situation where I drew the PocketTopo extended elevation in one orientation in the cave, and in XTherion, and then decided that the map should project the other way around.

Try searching for flip in the old forums posts, such as;

https://www.mail-archive.com/therion@speleo.sk/msg05041.html - Multiple Elevation Maps

https://www.mail-archive.com/therion@speleo.sk/msg05484.html -specify all the same

 

You could use revise to change extended elevation scraps to projected elevations (or just hard-code the scrap definition header to be projected to the orientation you want), where, as in your case, the projection you want to use is generally perpendicular to the passage alignment.

I thought I had put an example of this in the wiki years ago, or maybe the forum, but maybe not as I cannot find it now.

If there are survey legs not perfectly perpendicular you  will probably not like the local distortions, although you could use Martin’s tip in the wiki to tidy up zig zag surveys <https://therion.speleo.sk/wiki/tips#how_to_export_correct_extended_elevation_from_zig-zag_centerline>  in otherwise perpendicular passages.

 

Bruce

 

 

 

 

 

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