Two lucky factors let us navigate onward without having to painfully backtrack:
- Although we were out of mobile network range, my Google Maps app on my phone had cached some Terrain View tiles. (This is luck, unlike the regular base map layer, you can't intentionally download Terrain layer maps)
- In many areas Google's Terrain View derives its images low-resolution topographic maps, but in parts of Oregon and a few other places it uses LiDAR, a high-resolution elevation mapping technique. The LiDAR image (on the left above) revealed the topography of the real Corral Mainline so we were able to bushwhack up to it and get back on track.