2

I'm new with QGIS and GRASS so I'm sorry if there is a straightforward answer for this question but I can't seem to get it done.

I've imported a point cloud into QGIS from a datafile. Now I'd like to plot these data points into 3D by using GRASS.

First of all, I couldn't import the QGIS file into GRASS. What is the type of file I need to save the point cloud in QGIS, in order for it to be imported into GRASS?

Second, is it possible in GRASS to add multiple layers in order to create a 3D point cloud?

I really tried everything but the way I'm doing it doesn't quite seem to work.

  • Micha, First of all thank you for answering my question. Secondly, does the r.in.xyz command actually create a 3D "volume" like image? Or like with LIDAR data, create a surface? I would like to create an actual cloud with a lot of "borehole"-like data. So in other words, all of the 2000 (x,y) coordinate data will have about 10 to 50 different z values for the same x and y value. So the result I am aiming for is a real 3D image, not a 2.5D result. – Tom Mar 16 '15 at 14:01
  • If you have a new question, please ask it by clicking the Ask Question button. Include a link to this question if it helps provide context. – John Powell Mar 16 '15 at 14:19
2

If your original pointcloud data is an ascii x,y,z formatted text file, then GRASS has the module r.in.xyz for this kind of data. The steps are simple:

First run the module with the -s flag, which scans all the input data and give you the full extents of the data (min,max X and min,max Y).

Now set the region using g.region with the extents from above. You must be careful to set also the resolution to some value such that each cell will have at least 1 point from the point cloud. So, for example, if you data has at least one point per square meter, then you can set the resolution to 1 meter.

Next import the point cloud into GRASS, r.in.xyz using method=mean. This sets the elevation for each cell to the average of the point cloud values withing that cell.

Now for visualization, use the nviz module. And yes, you can "drape" other layers over the terrain raster created from your point cloud. More information on nviz here.

Your Answer

By clicking “Post Your Answer”, you agree to our terms of service, privacy policy and cookie policy

Not the answer you're looking for? Browse other questions tagged or ask your own question.