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If you have land tenure mapping, and you're only interested in the areas for which there are no polygons in a region, is there a way to query these areas out and create a shapefile from them.

A tangible example using Mining Claim Mapping:

Various forms of land tenure are represented for an area. These areas are captured with polygon geometry. Areas include Mining Claims, and various forms of Patented Mining Lands (ie - Surface rights only, surface & mineral rights, 11 year lease, etc, etc).

In this example, If I'm ONLY interested in the areas that are not captured (which would be Crown Land), how do I go about extracting that data (data which is "NOT THERE") without manually digitizing? Is there a way to do this with a select by location query? The only thing I can come up with is to use the bpoly command in AutoCAD, but this would be a bit time consuming and would also lend itself to the possibility of oversights/errors on the part of the user.

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    Is there a larger polygon for the region/area as well or is it composed of many smaller polygons? – Emily Aug 16 '11 at 15:09
  • @ Emily - It is composed of smaller polygons. The data are downloaded from an online site. I could very easily encase the study area with a large polygon if this solves the problem. Would it be feasible to paste the land tenure to the "Big Polygon Shapefile" then just use the cut tool? Does that make sense? – Dano Aug 16 '11 at 15:13
  • +1 Emily - I think your question prompted my brain to figure this out Emily! That's the way to do this isn't it? Just use the tenure to cut a hole in a bigger shapefile. – Dano Aug 16 '11 at 15:17
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    ok .... in all fairness, Emily was the first to respond, so I'll give it to her (but I plus-oned all of you). Sorry to have posted a question with such a simplistic answer too everyone. – Dano Aug 16 '11 at 15:46
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    Kudos to @Dano for upvoting all acceptable answers. We should all do that. Think about it: if someone makes an effort to research and answer your question, and any aspect of their contribution is useful (and not incorrect), doesn't it at least deserve that minimal recognition from you? – whuber Aug 16 '11 at 18:56
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What should be done, if you don't already have a larger study area polygon, is to create one. Then, clip/erase using the other tenure data the larger polygon to create the smaller polygons of your unused land.

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    +1 If you're still using ArcInfo workstation with coverages, you might be able to use the outside polygon to do the erase instead of creating a study area polygon. More modern geodataset formats, however, do not maintain a notion of outside polygon. – Kirk Kuykendall Aug 16 '11 at 16:47
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    @Kirk That's the merit of Emily's response: she points out one should already have a study area polygon, if only as a way of stating "my data end here." Sooner or later it becomes useful for processing or analysis, as this thread nicely illustrates. – whuber Aug 16 '11 at 18:59
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As @Emily was inquiring about, if you have a bounding polygon or as you call a region you can use this layer to come up with the difference to create the Crown Land polygon layer. To do this you could use the Erase tool to erase away your region layer against the land tenure features leaving the Crown Land layer.

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The only way I can think of is to create an averlaying single polygon (which covers all the area of interest).
Then perhaps the erase command using the big polygon as input and the smaller polygons for the erase layer.

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You can use the autocomplete polygon tool. Suppose there is a donut shaped feature, and you want to make another feature from it's hole in the middle. Select autocomplete polygon, click on one point of the inner circle, and then click on the same point (double click basically), it will follow along existing points and make a feature of that shape.

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I used the helpful suggestions on this page for an exactly similar situation I encountered: I had a pervious cover for a county which had gap areas for the impervious areas and I needed all the impervious area polygons. This is how I got what I needed:

  1. I created a bigger boundary shapefile and used the Erase tool (in ArcToolbox, go to Analysis Tools/Overlay) to obtain the impervious area polygons (i.e. gaps in the pervious data set). There was one issue with this resulting shapefile: all the polygons were in a single part and I needed them to be multipart so I could, for instance, calculate individual areas.
  2. I then used the Explode tool in Advanced Editing toolbar - Start editing session, select the single part impervious polygon and click the Explode icon. Now you have individual polygon parts for the impervious areas.

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