shrug-l: Close Contour Polyline's and edge

Greg Mauldin MauldinG at
Thu Mar 6 10:15:24 EST 2014

Hi Bret,

If you have Spatial Analyst, I would recommend using the DEM for your analysis rather than the contours. If you need to use the contours, and your analysis requires an area dimension, you will need to close the contours off and convert them to polygons. To do this, you could generate them using a wider area DEM, convert them to polygons and clip them to your area of interest, or you could snap them endpoint-to-endpoint at the edge of your existing DEM.

Generally, for topographic analysis over an area, a DEM works best because the Zvalues are recorded cell-by cell as a cohesive surface, which preserves to full detail in your elevation data. If you are working with polygons, you can only have one Zvalue per polygon, thereby losing whatever variation in elevation that may be present within the polygon boundary. This often results in highly generalized elevation data.

Feel free to call if you want to discuss.

Cheers, Greg

Greg Mauldin, GISP
GIS Project Manager
Tallahassee-Leon County GIS
Leon County Courthouse
301 S Monroe St, Room P313-F
Tallahassee, FL 32301
maulding at

"People Focused. Performance Driven"

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>>> Bret Whiteley <bretwhiteley at> 3/6/2014 9:51 AM >>>

Morning Shruggers,

This list has been very quite for some time - hope its still working. 

I generated contour lines from a DEM, and the lines are not closed where the contour reached the edge of the DEM. See the Graphic below which illustrates this, for one contour interval. I need to convert these polylines to polygons to continue with my analysis. To do this I need to "close" these lines so that are continuous. Is there an tool, or script that can do this for me? We have ArcINFO 10.2, with extensions. I feel like in the old days ArcSCRIPTS would have had the solution to this. 

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