I've already got QGIS (2.18.2) to
- add an ArcGIS shapefile with polylines
- create a polygon which is a buffer region around a subset of the polylines in the ArcGIS file
- add a KML file with one polyline
- reprojected the KML file into the same projection as the ArcGIS layer.
What I'd like to do is:
- split the polyline from the KML file into two layers: one with the parts of the polyline that lie within the buffer polygon, and another with the parts that are outside the buffer polygon,
- so that I can get the total lengths of the polyline within the buffer polygon and outside.
I tried to use the QGIS Geoprocessing > Intersection tool:
- with the buffer polygon as Input layer and polyline as Intersect layer, I get a polygon virtual layer with a bunch of features that don't make sense, and
- with the polyline as Input layer and buffer polygon as Intersect layer, I get
1005 See log for more detailsin the Log tab.
I'm concluding from this that the Intersect tool is meant for finding the intersection between polygons, not polylines and polygons.
I found a similar question that involves the Process Modeler, but am new to QGIS and going through the Training Manual (in lesson 12 now — looks like the Process Modeler is covered in lesson 17), so the Process Modeler approach is beyond me as I ask this question.
If there's a straightforward way to do this with tools other than QGIS+GRASS, I'd be happy to hear about alternatives, too.
Looking ahead (in case there are alternatives which have trade-offs down the line), I'd like to be able to automate this analysis so that
- instead of manually comparing one KML file's polyline against one polygon to find the polyline lengths inside and outside,
- I'd like to compare a set of hundreds of KML files' polylines against a couple of regions to find the lengths inside and outside the regions.
