Ten-foot contour lines on a uniform fill slope of 20:1 would measure how far
apart on a map with a scale of 1" = 40'?
1. 1.50 in
2. 5.0 in
3. 6.0 in
4. 7.00 in
The answer is 2. I'm confused. The way I see it, for every 20 feet of elevation change there
would be 1 foot of horizontal change. Therefore, an elevation change of 10
feet (ten-foot contour lines) would occur every 0.5 feet. I don't understand how 0.5 feet would
measure 5.0 inches with a scale of 1" = 40'.
I'm not confused anymore. I had 20:1 backwards. It's for every foot of elevation change there
would be 20 feet of horizontal change. I feel embarrassed! I was thinking rise over run, but
20:1 isn't the same as 20/1.
Carpenters doing a roof and surveyors doing roads use opposite notations for slope. Very confusing.
English units, slope ratios are expressed horizontal:vertical (20:1)
Metric slope ratios are expressed vertical:horizontal (1:20)
At least that that is typical around here.
Of course, none of this matters at all, since to an excavator, if there is a slope, it is a 1:1 slope, because "Your 20:1 slope only works on paper..."
