I'm currently trying to select bridges (line features), from a shapefile containing roads, which go across water (a polygon). The problem is when i try to select features crossing or intersecting the water polygon (both in arcgis and qgis), it includes roads on piers as well. It is not possible to manually select the features, as the dataset consists of approximately 1.5 million features.
What i have noticed is the lines on piers simply intersect/crosses the water polygons, while bridges i have found goes "through" the polygon (one part of a line feature enters through one polygon boundary, but the line feature also exits either through the same boundary or another boundary).
Is there any spatial operator/plugin that can select features going through the polygon instead of intersecting/crossing the polygon? basically a double-crossing spatial operation.
- edit: the road dataset does not contain any attributes to distinguish between different road "types"
- edit: As richard pointed out, it probably needs some graphic examples. Below are some simple visualizations of the red lines only crossing the green water polygon once (left) and red lines crossing the water polygon twice. I'm trying to get the double-crossing features.