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I am working with a set of LAS data which is irregularly shaped, picture a starfish as the point coverage, surrounding the starfish may be water on one side, may be more land elsewhere but no points were collected for it. In fact most of the areas around this starfish of points is land without points collected, and inside the starfish shape is a little lake.

I want to make a DEM of just the area where points were collected, and there are many ways of doing this, but most will interpolate all the no-point areas inbetween "arms" of the starfish data point pattern. Making the DEM by using a Terrain Dataset allows for the input of a bounding shape, to theoretically omit no-point areas from being interpolated and only geoprocessing inside of the boundary shape.

However, I have difficulty coming up with a precise bounding polygon of the outside edge of the starfish to use as my geoprocessing limiting extent.

I found a process online in a blog by Clayton Crawford which was picked up by ESRI and used as their help file for the process of turning LAS to DEM's, but it involves downloading a custom VBA script and several steps which went a bit over my head.

So I am wondering if anyone out there has a suggestion on how to get that starfish pattern of LAS datapoints inside a bounding starfish-shaped polygon, without the use of VBA, or alternately if there's a way to go right from LAS to DEM raster with no-point areas end up as NoData.

I'm using ArcGIS 10.1 for Desktop. Any suggestions on this are appreciated.

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How to create the Concave Hull around an irregular point cloud in Arc10:

  1. You have an input point cloud (for better performance > MULTIPOINT).

  2. Create a TIN: 3D Analyst > Data Management > TIN > Create TIN.

  3. Delineate TIN data area with a max_edge_length as parameter (this depends on the distance between your input points, e.g. I'm using 10m) and parameter "PERIMETER_ONLY": 3D Analyst > Data Management > TIN > Delineate TIN Data Area.

  4. Use the tool 3D Analyst > Conversion > From TIN > TIN Domain to save a polyline or polygon item outlining your TIN.

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If you have an Advanced level license of ArcGIS for Desktop then you could try using the Feature Outline Mask tool as suggested in this posting by Ask A Cartographer in response to:

I have a point dataset with about 17,000 points. I'm looking to create a footprint of the outer most points. I see one can create a convex hull, but my points form an irregular shape and the convex hull doesn't follow the path of the outer most points. Is there a way to do this?

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    @AndreSilva For this answer I'm only working off the documentation and web because I do not have access to an Advanced level license to test. The help says that the input is a layer so I think it would be worth trying direct on a LAS dataset layer first. – PolyGeo Sep 2 '14 at 23:26

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