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Data Acquisition and Management�Unit 5 – Topology� � �

Empowering Colleges:

Growing the Workforce

Based upon work supported by the National Science Foundation under Grants DUE 1304591, DUE 164409, DUE 1700496, DUE 1937177, Due 1938717 DUE 1937237, 2030206 and 2015927. Any opinions, findings, and conclusions or recommendations expressed in this material are those of the author(s) and do not necessarily reflect the views of the National Science Foundation.

Author: Wing Cheung

Title: Professor, Palomar College

Assistant Director, GeoTech Center

Email: wcheung@palomar.edu

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Source: Esri

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What is topology?

“…a collection of rules and relationships that, coupled with a set of editing tools and techniques, enables the geodatabase to more accurately model geometric relationships...”

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Source: (Zeiler, 2010)

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Why topology?

  • Preserve spatial integrity
  • Increase editing speed and efficiency
  • Identify and fix data errors

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Source: Esri

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How does it work?

  • Topological data model
    • Topological primitives
    • Spatial relationships
  • Topological editing
  • Locational queries

Sabi, & Muhammed, N & Zakari, S & Khalil, Muhammad. (2015). Vector Data Model in GIS and How It Underpins a Range of Widely Used Spatial Analysis Techniques. Dutse Journal of Pure and Applied Sciences 1(1) June 2015. 1. 122 - 132.

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Types of topology

  • Map topology
  • Geodatabase topology

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Map topology

  • Shared-edge editing
  • Quick and temporary
  • Use cases:
    • Modify the edge shared by water and land
    • Modify the edge shared by two fields

Source: Unsplash

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Geodatabase (GDB) topology

  • Choose from many topological rules
  • Stored in the geodatabase
    • Participating features must be in the same feature dataset
  • Use cases:
    • Check for gaps in congressional district polygons
    • Check for overlaps in zip code polygons

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What’s in a geodatabase?

Geodatabase

Feature Dataset

Polygon Feature Class

Geodatabase Topology

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See the entire poster at

https://tinyurl.com/esritopology

Source: Esri

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Examples of GDB topological rules

  • Between features in a layer
    • Lines must not self overlap
  • Between features from different layers
    • Polygons in one layer must not overlap with polygons in another layer
  • Between different geometries in different layers
    • Points in one layer must be covered by lines in another layer

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Source: Esri

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Properties of a geodatabase topology

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Properties of a geodatabase topology

Topology Name:

Name of the topology object to be created in the feature dataset in the geodatabase

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Properties of a geodatabase topology

Cluster Tolerance:

All features in the map should be at least this far apart from each other.

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Properties of a geodatabase topology

Ranks:

Controls feature movement when a discrepancy is identified.

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Properties of a geodatabase topology

Participating features:

Only feature classes in the same feature dataset as the topology object can participate.

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Properties of a geodatabase topology

Rules:

Can be enforced across different features, subtypes with one layer or across multiple layers.

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Error identification

  • Validate topology tool
    • Dirty areas
  • Errors identified in topology layer

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Error resolution

  • Show and fix errors with Error Inspector
  • Use suggested fixes or manually edit

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The geodatabase topology process

Build topology

Validate

Review errors

Fix errors

Created dirty areas

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Summary

Geodatabase Topology

Map Topology

Created and permanently stored in a geodatabase’s feature dataset

Created in a map and not stored anywhere

Only works on layers in the feature dataset

Works on layers stored anywhere

Can choose from a variety of rules

Mainly for shared-edge edits

Checks occur when running validation tool

Checks occur when editing

Fixes occur after validation

Errors prevented during editing

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See GeoTech Center website (https://geotechcenter.org) �for additional Model Courses and other curriculum resources. �This Model Course Is Licensed Under Creative Commons CC BY-SA ����� By: https://creativecommons.org/licenses/by-sa/4.0/ ��Note: some content is a derivative of other CC authors���

Author: Wing Cheung

Title: Professor, Palomar College

Assistant Director, GeoTech Center

Email: wcheung@palomar.edu

​