Ask A Cartographer

Calculate area between contour lines on conical features?

June 29 2011 | 0 comments
Categories: Map Data

Thanks for answering my earlier Q. However, I spoke too soon and my issue is not exactly resolved.

The previously described method ( I think would work on non-conical features. However, I am working with mountains. The attached image shows contour lines ranging from 300-600 meters depth around a conical feature. You'll notice that the polygon (which Arc gives me the area for) includes the area above 300 meters depth. I need a way to calculate the area of just the space between 300 and 600 meters. Is there some way to bound the upper contour? Or calculate the area of the terrain above 300 meters and just do simple subtraction?


Mapping Center Answer:

Ahh... line features that have coincident start and end points.  

So, I just tried this, but unlike the image you included, I processed all of the contours higher than the minimum value in the range I was interested in--just to make sure I was getting a polygon for each interval; and I did. 

So for your case, you just need to select the 300 and 600m contours and then run the feature to polygon tool and then select the outer polygon, which will contain the area.

That said if you get into an area of multiple peaks, just use select by location where you select the 700m contour to select the polygon that you don't need (or the 500m contour to select the polygons you do want).

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