This is the gradient analysis program from Ian Parberry, "Tobler's First Law of Geography, Self Similarity, and Perlin Noise: A Large Scale Analysis of Gradient Distribution in Southern Utah with Application to Procedural Terrain Generation". You will need to download DEM files from the UARGRC and run the Pack program on them to create UtahDEMData.bin before the thought of using this program should even consider the merest possibility of crossing your mind. Go look in the Pack folder in this archive.

This program reads a packed elevation data file called UtahDEMData.bin and records various interesting statistics in a tab-separated text file called output.txt. It must be compiled for a 64-bit target because it uses a quite large array to store the data. Don't execute it unless you have at least 16GB of RAM (preferably 32GB). A solid state hard drive is also recommended. Otherwise it may take a very, very long time to run instead of just a long time. On a good day on a fairly recent PC that has nothing much else to do at the same time, running downhill with a tail wind, assuming that the gods are with you and your karma is good and that your computer, in its infinite wisdom, doesn't decide on a whim that it must install 128 important updates and and shut down NOW, then it should take between 15 and 30 minutes to run. Otherwise your guess is as good as mine. This program does report various interesting things to the console so you can reassure yourself that it is actually working and not just hanging around hogging system resources.