Why does ArcGIS Desktop 10.2 add a "Shape_Length" field after running processes?
I'm unable to delete the field after as well. It isn't accurate either.
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2That's a system created field in feature classes. No, you can't delete it. Shapefiles do not have this field (although you can add one as a regular field). Can't speak for the accuracy. Maybe a coordinate system issue?– recurvataCommented Oct 9, 2015 at 15:17
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I've always just calculated geometry after the fact if I needed geometry and hide the Shape_Length field. Do you know the purpose of the field?– stanleykubrickCommented Oct 9, 2015 at 15:20
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The purpose is to indicate the length of the feature. As Chaz's answer says, the length units are the units of the coordinate system your layer is in, so they may be different than what you want but they are accurate.– Dan CCommented Oct 9, 2015 at 15:26
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1You can still hide the field.– recurvataCommented Oct 9, 2015 at 16:09
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1 Answer
Assuming that your data are being stored in a geodatabase the "Shape_Length", "Shape_Area", etc. fields are system fields that cannot be deleted and are maintained automatically by the geodatabase. These fields will use the spatial reference system units of the dataset (not the map document) so they should technically be correct (if not then we may need some more information to figure out why, i.e. what type of geometry?) but may not be in the units that you want.
If you do not want this field you could export to a shapefile (which does not maintain the same fields automatically and should allow you to delete). Or, you keep it in the geodatabase and just have to accept that you have an erroneous field and make your own field and calculate geometry on it to get a correct count.
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By default, geoprocessing results are stored in
C:\Users\<your username>\Documents\ArcGIS\Default.gdb, I think it's safe to say that's what happened here. One benefit to keeping your data in a geodatabase is that the Shape_Length field (and Shape_Area, if you're using a polygon layer) are automatically updated by ArcGIS when you edit the layer. So those length values will always reflect the real dimensions of your features.– Dan CCommented Oct 9, 2015 at 15:23 -
Do you know where I could check the default units its stored in? Commented Oct 9, 2015 at 15:32
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Right click the dataset in the table of contents in ArcMap or in ArcCatalog and go to the Source tab (if opened in ArcMap) or the XY Coordinate System tab (if opened from ArcCatalog) and look for the entry labeled "Linear Unit".– ChazCommented Oct 9, 2015 at 15:35
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Hmmm Angular Unit is listed but not Linear Unit. Is there any way to set the default Linear Unit to Km? Commented Oct 9, 2015 at 16:01
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2Angular Unit suggests that the data is in a geographic coordinate system rather than a projected one. You'll have to project the data to an appropriate projected coordinate system for the area. Use the Project tool in the toolbox. Commented Oct 9, 2015 at 16:13