Originally Posted by
I-Like-To-Bike
An 813 foot hill over 7.8 miles of horizontal distance would be a 1.975% elevation grade. The graph you posted shows no elevation close to 813 feet; are you adding up all the climbs, ignoring the descents, to come up with the 813ft. number? It may represent how many feet you climb overall, but does not represent the elevation grade of the hills.
The only place in NJ with a 47 percent grade may be from street level and up a 6" curb to the sidewalk.
Take a look at the picture again, and let me get you some math.
The starting point of that hill is 82 feet. The peak of it is at 194 feet. The total length of the rise is .05 miles, which is 264 feet.
(194-82) / 264 = 112 / 264 = .424, or a 42.4% grade.
arctan (.424) = 22.98 degrees.
Would you like more examples?