Slopes vs elevation

Slopes vs elevation

Elevation lines 🙁

While I was struggling with contour lines to figure out about the topography of a quarry, here is what I found…

The “Contour lines” is the representation of lines at the same elevation.

The lines correspond to regularly spaced levels. The contour lines and elevation map will give you some information about the topography and the slope, yet it could be improved… it is not precise since there is still some room for human interpretation.

Missleading information?

Look at this picture, would you be able to identify and “quantify” (!) exactly the areas where the slope is higher than what you can tolerate?

A critical slope is actually defined by its angle combined with its length. The elevation contour lines approach is not always suitable when you need to be sure and precise.

Mapping the slopes?

Look at this picture, the slopes are displayed with a palette of color going from blue to red. The yellow and red means “high slopes” angle, while the green is representing a lower slope angle and the blue would even mean “no slope”.

From my point of view, the advantage is clear. It is possible to identify the higher slopes, localy, and more than that, we can give a value and differeciate the slopes according to their respective value. There is no room for interpretation of contour and elevation lines.

Counting the “slopes of interest”

Now that we know the slopes map, – yes, I said “slopes map”, not “height map” 🙂 – it is possible to threshold that map in order to select the zones of interests. A basic threshold can be applied directly on it, thresholding the Z axis in order to keep the strongest slopes. In that case, the Z axis unit is a ratio where 0 is flat and the maximum slope is 1.

… and much more actualy.

Let’s go deeper with topography analysis

Having the right tool will definitely allow you to do just what you want, and more. So I am open to discuss with you if you have any questions regarding a tricky analysis.