Hi Nick,
Nick Whitelegg wrote:
Sometime, perhaps over Easter, I'd like to do something I've been meaning
to do for a while, and that is create "pseudo-Landranger" maps by combining
OS Vector Map District, contours from OS Landform Panorama, and OSM footpaths.
I will naturally be interested to see what you come up with!
The amount of data involved is large. I did mine on about 20 medium
Amazon EC2 instances, and it took a couple of days IIRC. This was with
my own code to parse the OS data and a renderer based on AGG.
One issue that I would like to look at at some point is how to "heal"
the contours. The lines in the OS download are truncated on steep
ground where they would be too close together on a printed map. (I
think that the 50m contours are always continuous.) I'd like to
"thread" these broken contours between their neighbours. I have some
vague ideas about how to do this; maybe something like:
- Make a Delaunay triangulation of all the points in all the contours.
- For each edge in the triangulation, if the ends have a height
difference of more than 10m, insert additional points equally spaced
along the edge.
- Re-triangulate including the new points.
- Discard all edges whose ends have different heights.
- The remaining edges are the new contours.
Has anyone here ever tried to do anything like this?
Regards, Phil.
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