- Use object placement tool to put an object on each corner of the river’s origonal course, then save the xml placement file.
- Open the xml in notepad, open Google Earth as well.
- Open Google Earth, under Tools>Options set Show Lat/long to Universal Transverse Marcator
- Put placemarks in the same co-ordinates as the objects, Copy & paste the corordinates from the xml file. In this case, I had to place 6 objects.
- Draw the river’s polygon so that it ended at the placemarks.
- Complile the KMl to bgl as normal.
This has worked well apart from a road that crosses the river, as well as a ridge in the water that stubbornly refuses to dissappear. I have noticed other ridges further upstream in Miicrosoft’s own river polygons; so maybe there is another fault not of my making.