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

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

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.

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.

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.

Case Study

83,000+ miles

of local roads in

the HUTF

inventory

greater than

60,000

legitimate

dangles

statewide

This issue is compounded at the state scale

Export Topology Errors --10.1

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.

•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.

February 7th. 2013 ArcGIS Resources

http://blogs.esri.com/esri/arcgis/2013/02/07/export-topology-errors/

A Perfect Solution?

“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”

-From ArcGIS Resources announcing the new tool (February 7th, 2013)

“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”

This sounds like the answer to all of our

problems

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

Using MS ACCESS, we can programmatically join a topology and Export Topology Errors feature class to update a new topology with known topology exceptions

The result effectively makes the topology layer

selectable by location

What you will need

-Personal Geodatabase containing

a) Linear Feature Class

b) New Topology

c) Feature Class from Export Topology

Errors

-MS ACCESS

The Solution

The Solution

Each feature contains 2 tables:

• Attribute Table (ObjectID)

• Shape_Index (IndexedObjectId)

ArcCatalog

Topology’s Shape Index Table

ACCESS Objects - Tables

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.

When you open the layer in ArcMap again,

only valid topology errors will display!!

T_1_PointError’s Table

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

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.

Questions?

Grant Garstka Grant.Garstka@state.co.us

Aaron Rhodes Aaron.Rhodes@state.co.us