Lecture 30/01/2017

Question 1

What are the 3 Geographic Entities?

Answer 1

1. Points
2. Lines
3. Areas

Question 2

What geographic entities best represent vector and raster file formats? Which is continuous, which is discrete?

Answer 2

1. VECTOR (point, line, area)
   •discrete
2. RASTER (grid/pixels)
   •continuous

Question 3

What does a vector model use to store the location of geographic entities?

Answer 3

Cartesian (i.e., x,y) or geographic coordinates (i.e., lat/long).

Question 4

What are lines?

Answer 4

A string of coordinate points that are connected by:

1. Nodes;
2. Vertices; and
3. Arcs.

Question 5

What are polygons?

Answer 5

1. A closed string of coordinate points that are connected by nodes and vertices and arcs.
2. Polygons also have size and perimeter properties.

Question 6

If you had to represent a small area with a big scale, would you use a point or a polygon?

Answer 6

point

Question 7

If you had to represent a small area with a large scale, would you use a point or a polygon?

Answer 7

polygon

Question 8

Provide an example of when a workgroup might require different geographic entities of the same geographic features?

Answer 8

A regional planner vs. an urban planner or traffic engineer require different resolutions of information at different scales (e.g., roadway details).

Question 9

Vector data models fall into 2 categories:

Answer 9

1. Topological

2. Non-Topological

Question 10

What is topology?

Answer 10

Topology is the geometric relationships that exist between entities located in space. It can be thought of as the study of how entities are organised relative to one another, whether they are: connected; adjacent; or contained.

Question 11

What does topology help us to do with spatial data?

Answer 11

Topology helps to detect errors in spatial data; topology is correct where lines connect with other lines, all polygons are closed, and no space should exist between adjacent polygons.

Question 12

What are the 3 aspects of topology?

Answer 12

1. Adjacency is the information about the neigbourhoods of different entities (e.g., properties which border each other)
2. Contained is the information about entities that enclose other spatial features (e.g., the boundaries of a water body).
3. Connected is the information about the links between entities (e.g., streets, roads, and highways).

Question 13

What detects slivers generated by digitizing?

Answer 13

TOPOLOGY!

Question 14

What’s the difference between Non-Topological Vector Data Structures and Topological Vector Data Structures?

Answer 14

Topological Vector Data Structures calculates the relationships that each geographic entity has to one another, where as Non-Topological Vector Data Structures are relative only to themselves.