I'd like to create polygon shapefiles to communicate elevation information on regional maps. I find these draped over a hill shade layer provide one of the best base maps.
I can tell some cartographers are creating these by hand by digitizing vector features over raster maps, but others are clearly created automatically.
Currently, I am using the following procedure:
- Convert contour lines from a single part to multipart
- Polygonize multipart contour lines
- Join contour data to new polygonized contours
- classify based on elevation
- simplify as required
I'm having a couple of problems creating these layers (in QGIS):
- Creating polygons from closed contour lines (not line segments) is fine, but if the line has a start and end point, it is not a feature with an area that I can create a polygon from.
- Contour interval data is dropped during conversion, so I have to join the original contour lines to the new polygons to include this information.
I think I have ways around all these problems, but I'd like a quick and easy way to do these conversions since it's a procedure I plan to do for many locations.
Does anyone know of a script that may expedite this process, or a guide demonstrating the preferred way to achieve this result?