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I have flown topo lines covering a large AOI. Some of these lines stretch across the whole area and therefore aren't closed while others just cut off and also aren't closed. I want to calculate the area of the lowest 5 contour lines per each basin (polygon).

I tried extending the lines and then converting them into polygons but this didn't work because some of them did not close.

How do I find the lowest 5 lines per each basin (there are about 35)?

I am using ArcMap 10.3 and AutoCAD Civil 3D. My company does not have the spatial analyst package.

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    Welcome to GIS.SE! Which software are you using? – underdark Sep 1 '16 at 18:46
  • Thank you! I am using ArcMap 10.3 and AutoCAD Civil 3D however, my company does not have the spatial analyst package. – jama Sep 1 '16 at 18:50
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    Welcome to GIS SE. Please edit the question in response for requests for clarification. It's also policy to have one question per Question. Please take the 2-minute Tour which explains how things work here. – Vince Sep 1 '16 at 19:00
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I'll answer 1 of your questions. If you only have 35 lines per basin, query by basin type, sort your table, and select the 5 lowest elevations. Done. For 35 records per basin, is it worth the effort to automate?

If you had more records to deal with, I would suggest creating summary statistics and using them to create a nested SQL query to select the 5 lowest elevations in each basin. If you're interested, there is documentation on that here:

Summary Stats: http://resources.arcgis.com/en/help/main/10.1/index.html#//00080000001z000000

Grouping with summary stats: Perform a group by query on geodatabase in ArcMap

Subqueries: http://desktop.arcgis.com/en/arcmap/10.3/map/working-with-layers/building-a-query-expression.htm#GUID-D1BFDC51-62DD-4090-B5AC-826FCF766F6A

If you need to assign the basins to the lines, use the intersect tool and set Join Attributes to ALL.

  • After researching the queries a bit more, the best solution to automate this would be a search cursor. Let me know if you're interested and I'll provide a code sample. – jbalk Sep 2 '16 at 5:51

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