7 - Spatial data structures

Question 1

4 levels of abstraction

Answer 1

1. Real world
2. Data model
3. Data structure
4. File structure

Question 2

Spatial data model

Answer 2

Simplified representation of spatial
features or spatial phenomena on the Earth’s surface

Question 3

Topology refers to

Answer 3

The spatial relationships that exists between features in a feature layer in the vector model

Question 4

Topology is the

Answer 4

• Connection between lines,
• Shared boundaries between areas
• Inclusion of points in areas

Question 5

Digital models used to store vector objects

Answer 5

1. Georelational Model
2. Object Based Data Model

Question 6

Georelational Data Model includes

Answer 6

Geometry (spatial features)
Attributes (relational data)

Question 7

File formats in which maps are created from ARCGIS

Answer 7

Arpx & MXD

Question 8

Arpx & MXD store..?

Answer 8

• maps
• symbology,
• layout
• hyperlinks
• toolbars added,

Question 9

files required to make a shapefile

Answer 9

1. .shp,
2. .shx
3. .dbf.

Question 10

Advantages of the georelational shapefile

Answer 10

• Display faster
• Non-proprietary & interoperable

Question 11

Disadvantages of georelational shapefile

Answer 11

• Shapes can overlay
• Boundaries must be stored twice
• Very little error checking
• Data quality issues

Question 12

A coverage def

Answer 12

Georelational data model that stores vector data - contains both the spatial (location) and attribute (descriptive) data for geographic features.

Question 13

When was the coverage introduced?

Answer 13

ArcInfo in early 80s

Question 14

How many files in the coverage?

Answer 14

12

Question 15

OODM

Answer 15

Object Orientated Data Model
- treats geospatial data as objects

Question 16

Property def

Answer 16

Describe an attribute of features in layer

Question 17

Method def

Answer 17

Performs an action to layer

Question 18

Feature class def

Answer 18

Store spatial features of same geometry

Question 19

Feature dataset

Answer 19

Store features that share extent and coordinate system

Question 20

How is OODM different from Georelational Model?

Answer 20

• Feature geometry (stored in special field = BLOB) & attributes are stored in one system.
• allows spatial features to be associated with a set of properties and methods

Question 21

BLOB

Answer 21

Binary large object data type

Question 22

Feature class

Answer 22

Store spatial features of same geometry

Question 23

Feature dataset

Answer 23

Store features that share extent and coordinate system