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Beyond the Legitimate Dangle Impasse:
how to really share and maintain topology exceptions with the
Export Topology Errors...
Introduction
Legitimate Dangles - line feature
termini, such as cul-de-sacs
“Must Not Have Dangles”
topological rule -- he...
Must Not Have Dangles

A line from one layer must touch lines from the same layer at both
endpoints.
Any endpoint where th...
Must Not Have Dangles

A line from one layer must touch lines from the same layer at both
endpoints.
Any endpoint where th...
Case Study
•

Arapahoe County contains 4,096 legitimate dangles

•

CDOT knows there are 4,096 dangles marked as exception...
Case Study
This issue is compounded at the state scale

83,000+ miles
of local roads in
the HUTF
inventory

greater than
6...
Export Topology Errors --10.1
February 7th. 2013 ArcGIS Resources

Overview

•Exports the errors from a geodatabase
topolo...
A Perfect Solution?
“the outputs of the Export Topology
Errors tool are standard feature classes,
which enable [the user] ...
The Real Problem
topology layers are not selectable and
cannot participate in spatial queries

topology errors are not act...
The Solution
Using MS ACCESS, we can programmatically join a
topology and Export Topology Errors feature class to
update a...
The Solution
Each feature contains 2 tables:
• Attribute Table (ObjectID)
• Shape_Index (IndexedObjectId)

ArcCatalog

Top...
The Solution
1) Design a Query with the following joins:

2) Make it an Update Query with the
following expression:
3) Run...
The Solution
The topology layer is now updated with known
topology exceptions.

T_1_PointError’s Table

When you open the ...
The Solution Summary
Create Personal GeoDatabase
Create, validate, and review topology
Export Topology Errors/Exceptions
M...
Some Issues
•

In MS ACCESS, only change the values in
the tables - not the schema

•

Performance hit in ArcMap on the li...
Questions?

Grant Garstka
Grant.Garstka@state.co.us

Aaron Rhodes
Aaron.Rhodes@state.co.us
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2013 Tips and Tricks Track, Beyond the Legitimate Dangle Impasse: how to really share and maintain topology exceptions with the Export Topology Errors geoprocessing tool by Grant Garstka

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Legitimate dangles created by line feature termini, such as cul-de-sacs, are a longstanding problem for GIS professionals who regularly work with linear feature data. When a topology is validated for the rule “Must Not Have Dangles” and all dangles are resolved or marked as an exception, the new Export Topology Errors geoprocessing tool in ArcMap10.1 allows for the ability to share the topological errors and exceptions with others. Sharing a Topology Error dataset is useful for fixing errors in the base layer among co-workers, but it does not help to track known topology exceptions. Once the fixed base layer is re-evaluated against a topology, any information known about legitimate dangles will be lost and reflagged as an error. This will necessitate the reevaluation of every dangle. For the case of CDOT, we are aware of ~60,000 known legitimate dangles across the statewide local roads layer, but a county-by-county workflow results in losing information about legitimate dangles every time a new topology is created or validated. Therefore, legitimate dangles have to be continually reevaluated - a huge waste of CDOT resources. The crux of the issue is the that topology layers are not selectable because they are only graphical representations of error locations. This presentation demonstrates a way to programmatically update a new topology with known topology exceptions using MS ACCESS. The result effectively makes topology layers selectable by location in order to incorporate known topology exceptions into a new topology and eliminates the need for repeat evaluation of legitimate dangles.

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2013 Tips and Tricks Track, Beyond the Legitimate Dangle Impasse: how to really share and maintain topology exceptions with the Export Topology Errors geoprocessing tool by Grant Garstka

  1. 1. Beyond the Legitimate Dangle Impasse: how to really share and maintain topology exceptions with the Export Topology Errors geoprocessing tool GIS in the Rockies 2013 October 9th Presenters: Grant Garstka • Aaron Rhodes
  2. 2. Introduction Legitimate Dangles - line feature termini, such as cul-de-sacs “Must Not Have Dangles” topological rule -- helps to identify the location of all dangles While the rule finds dangles, a user must determine if each dangle is an error or legitimate dangle
  3. 3. Must Not Have Dangles A line from one layer must touch lines from the same layer at both endpoints. Any endpoint where the line does not touch another line is an error.
  4. 4. Must Not Have Dangles A line from one layer must touch lines from the same layer at both endpoints. Any endpoint where the line does not touch another line is an error.
  5. 5. Case Study • Arapahoe County contains 4,096 legitimate dangles • CDOT knows there are 4,096 dangles marked as exception and their location, we do not want to have to ever revisit them. • Yet, if we create a new topology for this county’s layer and re-validate all 4,096 legitimate dangles will be flagged again as potential errors • This is the legitimate dangle impasse - a huge waste of CDOT resources.
  6. 6. Case Study This issue is compounded at the state scale 83,000+ miles of local roads in the HUTF inventory greater than 60,000 legitimate dangles statewide
  7. 7. Export Topology Errors --10.1 February 7th. 2013 ArcGIS Resources Overview •Exports the errors from a geodatabase topology to the target geodatabase. •All information associated with the errors and exceptions, such as the features referenced by the error or exception, are exported. http://blogs.esri.com/esri/arcgis/2013/02/07/exporttopology-errors/ •Exported feature classes can be accessed using any license level of ArcGIS. •The feature classes can be used with the Select by Location dialog box or the Select Layer By Location tool •Can be shared with other users who do not have access to the topology itself.
  8. 8. A Perfect Solution? “the outputs of the Export Topology Errors tool are standard feature classes, which enable [the user] to select the error shapes interactively or through a query, use those geometries for subsequent spatial queries, and share the errors with other users” “For example, [the co-worker] can... resolve a Must Not Have Dangles line error by snapping lines properly. After she finishes her edits, I can reintroduce the updated feature classes into the main geodatabase and use my Standard or Advanced license to rebuild the topology, check for remaining errors, and repeat the sharing process as needed” This sounds like the answer to all of our problems -From ArcGIS Resources announcing the new tool (February 7th, 2013)
  9. 9. The Real Problem topology layers are not selectable and cannot participate in spatial queries topology errors are not actually features, but rather graphical representations of error locations the Topology Exception feature class created from the Export Topology Error tool cannot be used to create a selection set in the topology Tool is geared toward resolving errors and not managing and tracking exceptions
  10. 10. The Solution Using MS ACCESS, we can programmatically join a topology and Export Topology Errors feature class to update a new topology with known topology exceptions What you will need -Personal Geodatabase containing a) Linear Feature Class b) New Topology c) Feature Class from Export Topology Errors -MS ACCESS The result effectively makes the topology layer selectable by location
  11. 11. The Solution Each feature contains 2 tables: • Attribute Table (ObjectID) • Shape_Index (IndexedObjectId) ArcCatalog Topology’s Shape Index Table ACCESS Objects - Tables
  12. 12. The Solution 1) Design a Query with the following joins: 2) Make it an Update Query with the following expression: 3) Run!
  13. 13. The Solution The topology layer is now updated with known topology exceptions. T_1_PointError’s Table When you open the layer in ArcMap again, only valid topology errors will display!!
  14. 14. The Solution Summary Create Personal GeoDatabase Create, validate, and review topology Export Topology Errors/Exceptions Make new topology or use Co-workers topology Open .mdb in MS ACCESS Join based on X,Y and ObjectID/IndexedObjectID Run Update Query on “isException” Re-open ArcMap
  15. 15. Some Issues • In MS ACCESS, only change the values in the tables - not the schema • Performance hit in ArcMap on the linear feature, not the topology? • CDOT was moving towards File GeoDatabases and away from Personal GeoDatabase.
  16. 16. Questions? Grant Garstka Grant.Garstka@state.co.us Aaron Rhodes Aaron.Rhodes@state.co.us

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