4d. Managing topology

1. Introduction

2. Setting up your project

3. Creating data (first steps)

4. CREATING AND EDITING DATA

4a. Loading data and the Editor toolbar

4b. Creating points

4c. Creating and editing lines

4d. Managing topology

5. Creating polygons

6. Preparing a print-quality map

4d.  Managing Topology

As you are creating your lines, open up the Topology toolbar: Customize –> Toolbars –> Topology.  Here’s the topology toolbar, in all its glory:

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If you mouse over the icons, a small dialog will pop up telling you what these tools do.  The ones that you’ll be concerned with here are the “Validate Topology In Specified Area”, “Validate Topology in Current Extent”, and “Fix Topology Error Tool”.  As you’re creating your lines, it’s good to manage the topology and fix errors as you go along.  Here’s how that is done:

1.  Zoom to a spot on your map where you have multiple lines that don’t intersect.

2.  In the Topology toolbar, click on “Validate Topology in Current Extent”.  This looks for any errors in the current extent of the view in ArcMap.  Or you can simply “Validate Topology…” as you go along.

3.  Errors will show up as pink boxes.  Use the “Fix Topology Error Tool” to select the errors you want to fix.  Once selected, the pink boxes will turn black.

4.  Right-click on one of the black boxes to bring up a menu that will give you options on how to fix the error(s).

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Depending on the error, there will be different was of fixing it.  I’ll let you figure these out by trial and error- the same fix doesn’t always work every time for every person/ topological error.  One thing of note though:  If you “Snap” your lines together while fixing topology, a “Snap Tolerance” window will pop up.  The tolerance is basically a radius (in map units) that Arc will look around the error to find other vertices to snap the line to.

5.  One thing worthy of note- ArcMap does not like closed loops (a polygon loop that is a singular line).  If you have any closed loops, the ends of the line will show up as topology errors, but with no way to fix them.  Simple fix- Go to the Editor Toolbar and select the “Split” tool.  Click on the loop line to split it into two separate lines.  Now you can fix the topology error.

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6.  Continue this process of creating lines and managing your topology until all the lines on your geologic map have been digitized.

7.  Editor –> Save Edits.

8.  Editor –> Stop Editing.

9.  SAVE YOUR PROJECT. 

You have been remembering to do this all along, right?

NEXT:  Creating Polygons

Previous: Creating and editing lines

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