Moving right along....
This distance between these two spot elevations is 50 right?
Let's assume that the elevation of the two spot elevations is 88.9 and 76.9 OK? Subtract 76.9 from 88.9 and what do you get? 12.0 right?
Now subtract 80 (the contour interval you are solving for) from 76.9 and what do you get? 3.1 right?
Are you with me so far or do we have to take a break?
bracken2: A quicker response would definitely speed things up here don't you think?
Continuing at a frenetic pace.The distance (d)has to be solved for. This is the distance from the spot elevation of 76.9 to our 80 foot contour. It goes like this:
12.9166 or (rounded off) 12.92
Measure north 12.92 and put the symbol for your contour interval at this location.
Do you follow this or not?