Hello @Bochen ,
Thank you for providing your DEM! After a careful review of your DEM and a review of the source code of our slope function, I conclude that slope is, in fact, being calculated correctly. However, the definition of S_i for which you provided a screenshot, has been slightly updated.
The reason I think the slope value is being calculated correctly is that the range of allowable slope values is (0, \infty). The slope values represented here are percentage slope. A 45-degree incline represents 100% slope. A 71.6 degree incline would be 300% slope. A slope value of 440% is allowed, and it represents that there are places where there is an approximately 75-degree incline. There are several places on your landscape where the difference between two neighboring pixels is very, very large: >50m elevation gain over only 12.5m change in distance! 50m change over 12.5m would represent a percentage slope of 400%.
So, I do not think there is an issue with the slope calculation.
The updated S_i definition in the user’s guide is:
Hope this helps, and please let us know if you have any further questions.
James