Limit contours to a maximum radius from topo point

[gdt]

When one's data is irregular, the plugin will draw contours in all regions which are between topo points, even if that is not sensible. An example is a set of points every 4m or so along a driveway, on both edges. The result mostly makes sense, but in one particular case, given a gentle curve, there is a crescent-shaped area about 50m long and about 10m wide, and contours are drawn in it. I realize everyone's density and desires are different, but I'd like to see a "max radius" setting, that I could set to say 10m, meaning do not try to do anything in areas that are > 10m from a topo point. The plugin seems to not go outside a convex hull. I'm basically suggesting the max length of line to be considered for convexity, sort of like the enclosed bay rule in maritime boundaries.

On the other hand, interpolation between the driveway edge and topo points from a single line more or less 10m away look reasonable even if they are oblivious to actual intermediate heights. (Obviously I need more points, but this issue is about reasonable output with not enough data.)

One suggestion, offered without a lot of thought, is to have a setting for the max distance between points that a TIN edge will be drawn, on the theory that believing anything about what's in between doesn't make sense. The other is not to generate contour line points outside of a buffer from the topo points. I don't think it matters much - whichever is easier.

This is not really the same as #56, which is about "don't draw lines in buildings" rather than "hallucinate a bit less".