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I have mapped a lot of cirque glaciers, using polylines to mark the shape of them.

Now I need to Close these polylines, but I do not know how to do that.

I have tried converting them to polygons (which is what would be the best thing to do for me) but since my polylines are not closed, it does not work. Since I have over 70 cirques mapped, I can not close them all by adding more vertexes to each one. (That would take some time!) I am hoping there is a way to just automatically draw a straight line between each polylines two endpoints...

Can anyone help me?

I use ArcMap 10.2.1, and am a beginner.

Picture of the polylines that I need to close

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    Can you include a graphic to show an example of a polyline you are trying to close? Commented Apr 12, 2014 at 20:51

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When you digitize polylines if you want to make polygons from them is to make sure that they are crossing or activate the snapping environment (or directly draw polygons).

If it is too late, you can still clean your polylines using the Extend tool but you need standard or advanced licence to use this tool. If you don't, you can try with integrate, which will snap vertices within a given tolerance. WARNING Make sure that you work on a copy af your dataset if you use integrate, because of large tolerance can have unexpected "side effects"

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  • Integrate is very useful but can be dangerous. As you said, do it on a copy then check the results against the original. Most of the lines wont move but can be significantly displaced where there are intersections or near intersections and in the end you will probably need to fix a handful manually. Just remember, it's a copy so go hard, remember what parameters you used and delete the bad ones so you don't get confused later. Commented Apr 13, 2014 at 5:18
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After some testing, the fastest way I can find to do what you want is to digitize your blue lines as new polylines. All you need to do is snap to the endpoints of each cirque line to close off the areas that you want. It can be one continuos new line in cases like the bottom of your image, but if you don't want that middle cirque in the upper part of your image as a polygon you can't close off that area. The lines themselves don't have to be closed, just the regions you want as polygons. This should be faster than editing all 70 shapes individually to close them off. Once you've closed the areas, make sure you have a polygon feature in your map that is editable, select all of the lines, and use the Construct Polygons tool on the Advanced Editing toolbar (wrench icon). This should create polygons out of all of your closed regions.

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