Error in Min. Bounding Geometry results

Question

I'm getting consistent, weird results from using Minimum Bounding Geometry to make circle polygons. I'm not sure if a datum issue, but I'm leaning more towards something wrong with Minimum Bounding Geometry tool. Here's the situation:

Goal is to acquire diameter in meters from minimum bounding polygon circles.

Python script works as follows:

• Import Lat/Lon values with MakeXYEvent Layer (setting GeoCoordSys to D_North_American_1983)
• Copy Features
• Project points (to North America Albers Equal Area Conic)
• Create Min. Bound Polygons around groups of points (ranging from 2 to over 50 points in a group).

Results seem reasonable for most polygons, however there are a good portion that the resulting circles wrap the globe. In several cases the points are clearly grouped in a small area off the coast, and the polygon is covering an enormous area of land, not even overlapping points. This in combination with "inconsistent extent" error makes me think it's a datum/project issue.

Troubleshooting efforts so far include

1. Points used to create the erroneous min bound circle outputs do not appear to have unusual lat/lon values.

2. Running Min. Bound Polygon to create a convex hull on points that were consistently creating crazy circles. Convex Hull created seemingly reasonable results.

3. Using convex hull polygon as input for min bound circle, and created same enormous circle.

Have you seen this before? Is this a case of choosing the wrong projection/datum? An error in Arc? An error in Min Bounding Geometry tool?

Thanks for input!

Sharon

Answer 1

If you need the minimum area bounding circle, then look at this link (Bounding Containers). Make sure you are using projected coordinates. Shapefiles are supported, and it has been tested in ArcMap 10 but should work in 10.1. The fundamental python code for other platforms is included within the zip file.