joincto

Add Geometry Attributes in Arc Catalog Fails

Discussion created by joincto on Sep 7, 2015
Latest reply on Sep 10, 2015 by Dan_Patterson

I swear that every day I use ArcGIS I seem to find a new problem. Here is the latest.

 

Preamble

Running ArcGIS basic 10.3.1 on WIndows7 VM under parallels on MAcbookPro.

I have a feature class  that was created from Business Analyst BDS

Demographic Layer of Census Block Groups (CBG) by removing many of the fields

which were not of interest and by limiting the CBGs to only those in 3 states (spatial join).

As a result of this data reduction two new fields are added: Shape_length and Shape_Area.

I was puzzled that the values in Shape_Area did not remotely agree with a BA field named

Land Area, not did the ratio between them seem to be any sensible conversion ratio

like SqMiles/SqMeters. So I used a tool in ArcCatalog,

Tools=>Data Management Tools=> Features=>Add Geometry Attributes

which enables me to calculate something called the Area Geodesic.

I choose as units square meters, it calculates the result, which indeed did

not agree with the existing Shape_Area field.

OK. So just to check I thought I would just run the tool once more. I delete

the field just calculated and invoke the tool again. Now the tool dies.

 

Questions

1. Whenever one selects a subset of features  from a data source and exports those features

    to a new feature class (mine are all in a file geodatabase), new fields are added. In my case

    the features are polygons, and the new fields added are Shape_Area and Shape_Length.

    Why? If I wanted those fields I could use tools to calculate them.

2. What is Area Geodesic anyway? Is it more or less the same as the area assuming flat earth?

    (for a small region, say the size of a census tract or block group)

3. The values in these fields did not appear to be correct. Because quite a bit of time has elapsed

    since this feature class was created I cannot remember details such as whether the layer

    was re-projected to a different PCS or GCS. But how could the values be incorrect?

    Do they change if the PCS changes?

4. It is impossible to remove these fields. The "delete" button is greyed out. Why?

    I don't want them, and aren't they available as the "hidden" geospatial parameters

    in a feature class anyhow?

5. If one takes the newly created feature class and make a further selection,

    select by location, and export that new subset of feature, those special fields

    Shape_Area seem to be created a second time. So now I have two of them!

6. The Add Geometry Tool is now failing after working the first time

    I have screen captures of the results from this tool on the first (successful) invocation

   and the second (and all subsequent) failing invocations. They are attached.

 

PS

In the last 3 weeks or so I think I have posted to GeoNet every two days.

People must be fed up reading my stuff. (Thank you all for nonetheless

helpful suggestions) Is it just me? I can't believe I

am really doing things which put me at the bleeding edge of GIS.

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