I am currently using QGIS to try and prepare a series of equally spaced -- along the terrain slopes -- sampling points within various NVC (National Vegetation Classification) sites in the UK. I am using a NVC vegetation dataset which is in vector form; allowing me to select the individual vegetation sites I want to produce points grids for. Previously I have been using the 'regular points' tool however this appears to only create a grid of points in 2D, horizontally. I am however interested in the movement of small mammals across the land and hence want to create a grid of evenly spaced sample points measured across, up and down the terrain; specifically the elevation, to produce a 3D grid of sample points. On the ground, the 'regular points' tool is fine on flat land, but in the hills the points are no longer evenly spaced. I have access to a lot of the OS vector and raster data but I am not sure exactly how best to approach this problem.

closed as unclear what you're asking by whuber May 18 '15 at 20:28

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  • I'm not sure this is technically possible as stated, unless your terrain only undulates along one axis. For example, take a piece of graph paper and try to bend it in two directions. – phloem Nov 25 '14 at 21:47
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    Welcome to GIS SE. Is NVC = National Vegetation Classification? What are NVC vectors? What does "create a grid of evenly spaced sample points that takes into account the lay of the land" mean? Please clarify your question using the edit button. – Martin F Nov 26 '14 at 5:44
  • Do you want the slope distance (as opposed to the horizontal distance) between adjacent grid points to be fixed? Why? I agree with @phloem, i think it is only possible in one grid direction, not both. – Martin F Nov 26 '14 at 17:15
  • I reworded the question quite a lot. Sorry if it's too much, but i found it hard to understand what you were trying to ask. It's a very unusual question. – Martin F Nov 26 '14 at 17:36
  • Did you ever work out how to do this? I have a very similar problem. – user52251 May 17 '15 at 10:05

Poisson disc sampling via dart throwing ought to work for an arbitrary surface although so far I've only used it on planes and spheres myself. It's fairly slow though.

You generate random points over the surface retaining those which are at least some minimal distance from the others that have been accepted. Stop when you've had some large number of repeated failures.

I'm not aware of any QGIS plugins for this so you would probably have to implement it yourself.

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