for me the question is where is the gradient data coming from? Just seems to me that it is unrealistic for accurate info to be for all kinds of roads. I admit this sort of detailed planning doesnt appeal, but I just wonder how accurate things are, and how much time spent doing this compares to using other resources.
As pointed out earlier, Contour maps can show detailed info including gradients. Once you learn to read them it's as easy as pie. They're available on line to look at, but you have to pay for hard copies. The only issue is scale. If you're doing a long ride, you'll need to piece together a bunch of maps.
OTOH, you might reserve contour maps for those places you have a reason to believe might feature steep hills.