I want to find a 'point of inaccessibility' from a series of points, representing towns and villages in Scotland. Using FOSS GIS tools (QGIS, SAGA, GRASS, Postgres/PostGIS ... ).
This is the point furthest from any centre of population. This would be the centre of the largest circle which doesn't contain a town, but it will have a town on its edge.
There's a raster approach, which works - the GDAL Proximity filter.
Is there a VECTOR based way to do this? One that doesn't require rasterisation?
Here's my attempt with rasters...
- Start with a point layer in a suitable projection in meters (I'm using OSGB, 27700)
- Add a field called "one", and set to integer with constant value 1.
- Vector to raster , editing command to use -a one and using GEO rather than pixel. Make sure pixels are square!
- Create contours on the proximity raster (in this case, 1 km wide)
Here's what it looks like. I drew some candidate points by hand ;-)
I thought that dissolving repeated buffers (using the Multi ring buffer plugin) might work, but I suspect I don't have enough memory for this to work.