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Splitting contour lines

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#1
Mike Boruta

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What are some ways of splitting contour lines so that they can be colored to reflect a change in land cover (ex. blue contours over glaciers)? I've tried doing this in Illustrator's pathfinder but have had no luck. Cutting the the lines manually is not an option. (I'm also working in ArcGIS and Photoshop, if those tools might help.) Any tips?

#2
frax

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You could try to play with masks. Duplicate the contours and create a blue layer with everything, except the glaciers, masked out. And do the opposite on the main contours layer.
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Matthew Hampton

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Another method you could use is to prep the data on the GIS side first by intersecting the contour lines by landcover. Before you export to Illustrator classify/symbolize the contour lines by land cover (you can "select by color" in Illustrator and change to the appropriate color of choice).

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Mapper_Mac

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What are some ways of splitting contour lines so that they can be colored to reflect a change in land cover (ex. blue contours over glaciers)? I've tried doing this in Illustrator's pathfinder but have had no luck. Cutting the the lines manually is not an option. (I'm also working in ArcGIS and Photoshop, if those tools might help.) Any tips?



In ArcMap you can add a field in the attributes database, (call it something that makes sense to you) then select all of the contours that you want a different color and label them in the new column you made (something that makes sense to you). Then all you have to do is choose categories in the symbology tab of the layer properties and add the newly created attribute field to the list and symbolize it any way you want. You have to start an editing session in order to do this.

#5
sitesatlas

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You might have some success using blend modes and opacity (here's a tutorial). Blend modes control how colors interact with the colors on layers beneath them. It sometimes takes a lot of experimenting to get the right result, but it may be worth a try.
Michael Borop
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#6
Mike Boruta

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Thanks everyone! Matthew's method worked best for my purposes. I did most of it in ArcGIS (with spatial analyst.) Here's my procedure, in case anyone else could benefit:

1. Reclassified my land cover data to isolate the category I was interested in (reclassing it to "1" and everything else as "0").
2. Used "Raster to Polygon" tool to convert the land cover raster to a vector layer
3. Used "Intersect" tool to intersect the contours with the land cover vector layer
4. Changed the symbology of the resulting contour layer to category/unique values, using the "gridcode" in the value field so that I could select different colors for the "0" contours and the "1" contours (the ones that overlapped the land cover)
5. Exported this contour layer to Illy and adjusted the colors by using "Select Same - Stroke Color"




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