=====Terrain Modelling=====

====GDAL utilities====
[[http://therion.speleo.sk/wiki/doku.php?id=ifl#GDAL utilities|GDAL blurb]]

====TerrainTool====
A simple java app that makes terrain models in less than a minute, designed for use with survex and therion.  

[[http://therion.speleo.sk/wiki/doku.php?id=ifl#terraintool_seems_to_be_an_easier_alternative|Terrain Tool blurb]]

====Surface Profiles====
To create surface profiles, you can string together a series of regularly spaced fixed surface points from, either a gps overland trail (lat long elev), a series of points manually extracted from Google Earth, or generated with the help of [[http://www.gpsvisualizer.com/elevation]]

To use GPSVisualizer 
  - export a kml model of your cave (or a simplified representation) with therion
  - Upload the kml file to the online GPSVisualizer tool and request plain text output (it will replace the cave elevations with ground surface elevations)
  - copy-paste the data back into therion as fixed stations
  - join the fixed stations with nosurvey legs

A hint at how to get all these fixed point into a form that looks like a survey centreline in therion...
   centreline 
   cs lat-long
   grade BCRA3

   walls off 
   mark temporary   
   flags surface 
   # station-names 4wd01 [] # to avoid name clashes if required

   fix 	1	-42.0001724	171.9024155	572.6
   fix 	2	-42.00020492	171.9022789	574.04
   fix 	3	-42.00021414	171.9021513	574.04
   fix 	4	-42.00026879	171.9020413	575.01
   fix 	5	-42.00030752	171.901925	575.01
   #thousands of these, they are decimal degrees and metres

   data nosurvey from to
   1	2
   2	3
   3	4
   4	5
   5	6
   6	7
   #thousands of these as well, a spreadsheet makes them easy to generate

   endcentreline

   #Then just select this survey along with your cave when processing