This is tangential, but a cool tool/technique for map geeks nonetheless:
-Did you know you can estimate slope angles from topo maps? Like, more than "that's steep and that's not", more empirical even. If you've got maps printed at 1:24000, there's a slope meter inside the cover of this otherwise very cool book from
AIARE (American Institute for Avalanche Research and Education) You just match up the gap between the lines and read your slope angle. Careful reading and field checks show accuracy to 2-3 degrees. (disclosure: I teach AIARE courses, so kind of work for them)
-We scratched our heads for a while on how to deal with the 20m contour interval in parts of the Eastern Sierra (which, rumor has it, dates to the efforts on the 90's(?) to get the whole country metric)
-We found that, in older versions of National Geographic Topo, one can choose the scale at which one wants to print his or her maps. And in Europe apparently a common map scale is 1:25000 with 20m contours. We can print from Topo at 1:25000 and this tool from
Brooks Range Mountaineering has a scale to estimate slope angles on the maps that result. I find it all pretty cool!