Topology Flashcards
What problem inspired the development of topology?
Seven Bridges Puzzle
What is topology in a GIS?
A way to model spatial relationships to show how features share coincident geometry.
What is ArcGIS topology?
A set of rules used to manage spatial integrity of features.
Who developed concepts of topology?
Leonhard Euhler
What does topology rules do in a GDB?
Define and constrain how features hare coincident geometry.
What are topological primitives?
Nodes, edges, faces are fundamental entities with spatial relationships represented in a topology
Describe 4 main spatial relationships that topology can check:
adjacency, connectedness, containment, proximity
Two reasons why topology is important:
1) understand how locations relate to one another 2) manage data integrity
What are slivers?
small gaps or overlaps that can be created during GP operations.
What are the two types of topology?
Map topology and GDB topology
Where is map topology stored?
In an AGP project file.
Where is GDB topology stored?
In a FDS.
Does shapefile data format support GDB topology rules?
No.
Can shapefiles be managed using map topology?
Yes.
Know similarities and differences between Map and GDB topology:
- Map topology works with all levels of ArcGIS software, & works with shapefiles and FCs, don’t have to be in a
FDS, but only allows coincident features to be moved or edited & no topology rules, no validation is supported. - GDB topology stores rules, topology errors and exceptions as features. Rules define how features can interact and
can be validated to determine if any errors are present.
Where should all FC reside in a GDB topology?
In a FDS.
Can a FDS store multiple topologies?
Yes. But a FC can participate in only one GDB topology at a time.
Why is a GDB topology added to a map?
To view errors.
What are errors called when they persist in a topology?
Exceptions
What is a vertex?
Is located along an edge, defines the shape of line and polygon features, and can be edited.
What is XY cluster tolerance?
Distance range where all vertices are considered identical. When topology is validated,
the cluster tolerance is used to move coordinates of lower accuracy (if ranked) to locations of more accurate coordinates
within that tolerance.
How does ranks work in a topology?
If a FC is assigned a high rank (ex .1) the less the feature will
move during validation if two or more vertices fall within the cluster tolerance. If a FC is assigned a low rank (ex. 5) then
features within the cluster tolerance will move instead of a higher ranked feature.
