Difference between !shape.area! and Calculate Geometry > area

18488
35
05-18-2016 05:46 AM

I have a shapefile with 62.000 polygons.

I have created two fields (Double) AREA1 and AREA2 with identical properties.

On AREA1 I have calculated the area of polygons with Calculate Geometry > area process.

On AREA2 I have calculated the area of polygons with Field calculator and the command: !shape.area!

When I compare the difference between the two fields ([AREA1] - [AREA2]), I find 30 polygons with no zero difference less than 0,01 square meters.

Is there a different algorithm for these processes?

Does anyone know why is this happening?

35 Replies
DanPatterson_Retired
MVP Esteemed Contributor

does the file have a defined coordinate system?  problems in calculating shape geometry arise when there is no know coordinate system.  This is well documented on this site.

The shapefile has a coordinate system defined (Greek Grid).

I tried yesterday after publishing my question to calculate with and without defined Projection and the result was the same.

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DanPatterson_Retired
MVP Esteemed Contributor

Two things to check

  • the dataframe and file are in the same coordinate system
  • run a repair geometry on the file to correct any unseen geometry errors

The check geometry found no errors but I run Repair Geometry.

The dataframe in on the same coordinate system.

The difference remains!

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DanPatterson_Retired
MVP Esteemed Contributor

Pagagiotis.... export and post a  sample, I would be interested in seeing this vagrant shape set since I am interested in computational geometry issues.

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JoshuaBixby
MVP Esteemed Contributor

What version of ArcMap are you running?  It always helps to know the versions of software we are discussing.

I am using ArcMap 10.3.1 on Windows 10 Pro.

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DanPatterson_Retired
MVP Esteemed Contributor

any chance on the sample geometry?

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I will provide it tomorrow.

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