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What is the formula/equation of the average slope on a topographic map?

I was asked to find the average slope between two points on a contour. The equation that I found on the internet was: Change in elevation(in feet)/distance(miles) Is this true?

Public Comments

1. Yes. In Algebra the formula is known as rise over run or just rise/run. So, if Contour line A is 822 ft elevation; Contour line M is 201 ft. elevation; distance between A and M is 3 miles or 3•5,280 ft = 15,840 ft. The formula is: (822-201)/ 15840 = 620/15840 = 0.03914... or ≈ 3.9% slope