Exporting horizons from OpendTect to QGIS

This is a how-to for exporting horizon data from OpendTect to QGIS, for example for gridding.

Import (x,y,z) points into QGIS
Make sure you have the Add Delimited Text Layer plugin enabled in Plugins > Manage Plugins:



Make sure you have Interpolation plugin too, while you're there.

Find the plugin and click on its icon to start it. Fill out the form, being sure to select the right delimeters, and setting the X and U fields appropriately.



Set the CRS
There's a good chance the data do not appear, as you need to set the CRS for the layer. Right-click on the new item in the Layers menu (left in main window) and select Set layer CRS. The one you want is probably under Recently used coordinate reference systems at the bottom of the dialog.

When you have selected the correct one, the data points should appear on your map.



Grid the surface
If you want a complete surface, you need to interpolate.


 * 1) Be sure you have the plugin: QGIS > Plugins > Manage Plugins...
 * 2) This time, look for Interpolation plugin
 * 3) Start the plugin
 * 4) Set the vector layer to the newly imported points
 * 5) Set the Interpolation attribute to the data example that matches your Z column (the one that doesn't look like an X or Y)
 * 6) Click Add and ensure the Type is Points
 * 7) On to the Output... I get best results from Inverse Distance Weighting. By 'best results', I mean that TIN crashes QGIS.
 * 8) Click on the wrench to change the weighting parameter if you want. You will probably want to run a few versions to pick the best.
 * 9) The number of columns and rows are probably wrong. The easiest thing to do is probably just to ignore them and set the Cellsize paramters (which will be your bin size, unless you interpreted on decimated data in OpendTect)
 * 10) Provide an output file in a sensible place (you can't hit OK if it doesn't recognize the location)
 * 11) Make sure everything looks OK
 * 12) Hit OK
 * 13) Fix whatever is broken
 * 14) Hit OK for realz
 * 15) It will add the result, but you might need to fix its CRS, as you did for the points. This seems odd, I am probably doing something wrong
 * 16) The surface is probably grey — right-click on it in the Layers list and choose Properties; then you can choose a new colormap (Style > Color map > Whatevs)