Ok. So it looks like the geoprocessing functions really don't work correctly. In a typical GIS system, one can perform a Difference operation on a polyline shapefile and a polygon shapefile. I do this routinely in QGIS. However, the Difference function in MapWinGIS produces an unreliable result that does not reflect the true "difference".
If I have a road network of polylines, and I want to overlay this with a set of polygons and perform a Difference. The result should be a set of new polylines that have the sections overlayed by the polygons clipped from the lines. This is useful if you want to create a new road layer that shows where a viewshed polygon overlay impacts the ability to see certain segments of the road.
It's really too bad. Geoprocessing functions are central to a GIS system, and an inability to perform these functions reliably is regrettable.
If I have a road network of polylines, and I want to overlay this with a set of polygons and perform a Difference. The result should be a set of new polylines that have the sections overlayed by the polygons clipped from the lines. This is useful if you want to create a new road layer that shows where a viewshed polygon overlay impacts the ability to see certain segments of the road.
It's really too bad. Geoprocessing functions are central to a GIS system, and an inability to perform these functions reliably is regrettable.
