You are here: > ESRI Forums > arcgis desktop discussion forums > Thread Replies

ArcGIS Desktop Discussion Forums

ArcGIS Desktop - Data Editing forum

Cut Polygon Features doesn't split multi-pa...   Criterion Inc Jun 06, 2007
Re: Cut Polygon Features doesn't split mult...   Dan Patterson Jun 06, 2007
Re: Cut Polygon Features doesn't split mult...   Criterion Inc Jun 06, 2007
Re: Cut Polygon Features doesn't split mult...   Tomas Riesco GISP Jun 12, 2007
Re: Cut Polygon Features doesn't split mult...   Diane McConnaughey Jun 20, 2007
Re: Cut Polygon Features doesn't split mult...   Lisa Crowe Jun 22, 2007
Re: Cut Polygon Features doesn't split mult...   Criterion Inc Jun 25, 2007
Report Inappropriate Content • Top • Print • This Forum is closed for replies.    
Subject Cut Polygon Features doesn't split multi-parts in 9.2 
Author Criterion Inc 
Date Jun 06, 2007 
Message There is a new behavior in 9.2 sp2 that maybe someone could comment on. In 9.1 or below, you could selectively break up a multi-part polygon using the following edit session process:

1. Select a multi-part polygon
2. Choose the "Cut Polygon Features" edit mode
3. Draw a sketch line entirely around one of the component polygons making up the multi-part
(make sure the sketch line is a closed loop)
4. Finish the sketch.

This used to create two polygon features, but now at 9.2 when you try this is gives the "A polygon cut operation could not classify all parts of the polygon as left or right of the cutting line" error. No matter how one sketches this closed loop around one part of the multi-part, the same error occurs.

This operation isn't the equivalent of the Advanced Editing "Explode Multi-Part Feature" tool since doing the cut this way allowed you to selectively split off only one or two polygons of a multi-part that might have dozens of component parts, whereas Explode breaks the entire multi-part shape up.

Try this (SHP, PGDB) in a 9.2 ArcMap edit session and get the attached error message (rtf screen caps inside zip).

Why has this behavior of the "Cut Polygon Features" edit mode changed? How can I selectively break up multi-parts?


UPDATE: the screen cap in my attached rtf incorrectly shows a non-closed loop, but the error message occurs (and did not occur prior to 9.2) when you draw a sketch line that snaps to itself at its beginning vertex in a closed polygonal loop... 
  CutErr_ScreenCap.zip (opens in new window)
 
Report Inappropriate Content • Top • Print • This Forum is closed for replies.    
Subject Re: Cut Polygon Features doesn't split multi-parts in 9.2 
Author Dan Patterson 
Date Jun 06, 2007 
Message does "Check Geometry" tool in arctoolbox report any errors? 
  Geomatics, Carleton University, Ottawa, Canada 
   
Report Inappropriate Content • Top • Print • This Forum is closed for replies.    
Subject Re: Cut Polygon Features doesn't split multi-parts in 9.2 
Author Criterion Inc 
Date Jun 06, 2007 
Message Dan, thanks for your reply. "Check Geometry" produces a DBF with no rows beyond the header row. I've tried to do the closed loop Cut on numerous polygon data sets (shp and geodb), all of which worked fine in 9.1 and all of which now fail in 9.2... 
   
Report Inappropriate Content • Top • Print • This Forum is closed for replies.    
Subject Re: Cut Polygon Features doesn't split multi-parts in 9.2 
Author Tomas Riesco GISP 
Date Jun 12, 2007 
Message I have the same error traying to cut a polygon. 
   
Report Inappropriate Content • Top • Print • This Forum is closed for replies.    
Subject Re: Cut Polygon Features doesn't split multi-parts in 9.2 
Author Diane McConnaughey 
Date Jun 20, 2007 
Message I observed the same problem when trying to use the cut polygon in 9.2. My small multi-part polygons had been merged with the wrong polygon, do to fat fingers. When I tried to explode the multipart, my ArcMap session exploded instead. So I created a new polygon around the small multi-parts I wanted to split out, merged them with the appropriate polygon. My topology rules did not allow for overlap, and allowed me to select the now overlapping polygons and merge them with the correct polygon. 
   
Report Inappropriate Content • Top • Print • This Forum is closed for replies.    
Subject Re: Cut Polygon Features doesn't split multi-parts in 9.2 
Author Lisa Crowe 
Date Jun 22, 2007 
Message Thanks for submitting this issue to technical support, if you wish to track this issue the nimbus number is NIM009849. Currently there is a developer sample called 'Convert part to feature'
This sample converts a selected part to its own feature. For example, if a feature has ten parts, a particular part can be removed from the original feature and turned into its own feature. The sample is available in VB6, as well as the .net languages in Visual Studio 2005
For the .net version see the following link,
http://edndoc.esri.com/arcobjects/9.2/NET/0360665a-35c2-4b7e-948e-c9bceadae3ac.htm
For VB6,
http://edndoc.esri.com/arcobjects/9.2/CPP_VB6_VBA_VCPP_Doc/COM_Samples_Docs/Editing/Edit_Sketch_Context_Menu/Convert_Part_to_Feature/c8745ca2-eea3-4733-b3da-0697ff212706.htm

Thanks,
Lisa Crowe
ESRI 
   
Report Inappropriate Content • Top • Print • This Forum is closed for replies.    
Subject Re: Cut Polygon Features doesn't split multi-parts in 9.2 
Author Criterion Inc 
Date Jun 25, 2007 
Message Lisa, thanks for your reply.

To bring anyone following this thread up to speed, I'll relay the responses I've received directly from ERSI tech support.

This was their first response from 6/14:

"The behavior that 'worked' at 9.1 and earlier was unintended; the Cut Polygons task was not designed with this workflow in mind. We changed the implementation of Cut Polygon Features at 9.2 to address some problems with supported workflows, which inadvertently changed the behavior documented here.

The issue is an example of a workflow that worked incorrectly or not by design. During this time, some users have become accustomed to this workflow. When the issue had become fixed and resolved for ArcGIS 9.2, some users misunderstood the original behavior of the function.

Currently, the Cut Polygon Features is working correctly and as designed for ArcGIS 9.2."





Given that their opinion was that this workflow for selectively splitting off polygons from a multi-part was, in effect, "doing it wrong", I then asked them to explain what they thought was the way to "do it right". This is when NIM009428 was created. Before Lisa's response above was submitted, tech support sent me this message on 6/21:

"As a result of the change in functionality at 9.2, I've created an enhancement request regarding this issue. It details the prior functionality, what changed, and the current workaround which is less then ideal. Please use the following enhancement request to track this issue -> NIM009849.

I would also encourage you to touch base with your ESRI sales rep in regards to the importance that issue be addressed.

The only way we can see to go about this via the GUI is to do an explode on the multi feature, then a merge the polygons back together that you didn't intend to split away.

Something like this could also be done through code, however, management of the attributes would have to also be managed. Please let me know if you need any help getting started with this."




This reponse correctly identifies the problem with Lisa's developer sample workaround: field management using attribute domains. Lisa's developer sample code simply uses a boiler-plate loop for copying field values verbatim from the existing multi-part feature to the newly created feature. The user is made to become responsible for manually managing any Split/Merge policies defined in a personal geodatabase domain and applied to a feature class field. This renders Split/Merge domain policies ineffective: if they only work on actions which respond to the IFeatureEdit::Split method, and we're being asked to use an alternative to IFeatureEdit::Split in some situations, then attribute domains are unreliable for handling edits in our geodatabases.


I guess it's not surprising that a similar issue came up in the implementation of Topology editing tools:

http://forums.esri.com/Thread.asp?c=93&f=1741&t=198483&mc=2#msgid592604


This is a step backward. The workflow used before 9.2 for splitting multi-part polygons ensured that attribute domains successfully managed field values in the broken up parts. However ESRI is telling us this workflow was wrong. If their solution is to have us use a workflow that does not allow any attribute domain to perform its function, are we not also being told that we shouldn't be using attribute domains? Have attribute domains themselves "become fixed and resolved for ArcGIS 9.2" since their usefulness in 9.1 and below were "an example of a workflow that worked incorrectly or not by design"?

If not, many users out there could use generic, polymorphic sample code for manually managing field updates such that attribute domains are looked for and obeyed if present. I'll take that sample and overhaul the code in my polygon feature class editing events to handle this situation manually until the "enhancement" (which is a return to the way things were before 9.2) request is fulfilled.