Extended elevation (PocketTopo) to projected elevation (SVG)
Select file to convert (Therion export from PocketTopo)
OR alternatively paste your file
Projection bearing
In degrees, eg. 0 is West-East, 90 is North-South

Intended usage

The converter is supposed to help surveyors to draw projected cave profiles from their extended elevation sketches.


The input is expected to be a Therion PocketTopo export (Export / Therion...). After a successful conversion, the program will output a SVG file.

To convert the sketch, the centerline is first projected onto the specified surface. Then, for each centerline shot the program processes a small vertical fragment of the input sketch between the two stations involved. The fragment is scaled horizontally, according to the direction the shot is 'seen' from. If necessary, the fragment is flipped horizontally (this happens when the viewing angle causes the shot to be observed 'from behind'). The processed fragment is then placed accordingly on top of the projected centerline.

Due to the complicated nature of the conversion, the resulting sketch will almost always require manual edition, probably by someone who has been at the spot. Special attention is needed when the centerline 'reverses' direction, as well as in places where elevations of a few side passages are superimposed on each other in the source sketch. In the latter case, the converter has no means of detecting which sketch line corresponds to which passage. The sketch fragments are therefore converted multiple times and stacked together. The cartographer has then to use his own reasoning to select proper lines from a bunch of nonsense.

The output scale is always 1:1000.


  1. Run PocketTopo and load your measurement data. From the menu, use Export / Therion... and save your data as text file in the Therion format.
  2. Load the resulting Therion file into this converter
  3. Enter your desired projection bearing
  4. Click Convert
  5. Open the output file in Inkscape and enjoy.