11: Vector I Flashcards Preview

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Flashcards in 11: Vector I Deck (17)
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1
Q

LINE GENERALISATION

A

reduction of level of detail in data as to gain clarity in information

  • reduce data noise, enhance relevant patterns
  • reduce volume of data without adversely affecting its use
  • make things as simple as possible but not simpler (Albert Einstein)
2
Q

SPATIAL QUERIES

A

simples operational capabilities of any GIS

immediate answer to a map/database query:

  • how many X are within Ykm of this point?
  • which is the closest X to Y?

Two typical types of GIS queries:

  • spatial queries by geometry
  • spatial queries by data attribute selection

GIS can answer these questions because of geometry and topology

3
Q

BUFFERING

A

based on concept of proximity

separates a map into two areas:

  1. within specified distance of selected map features
  2. not within specified distance of selected map features

buffer zone - area within the specified distance

selected map features for buffering may be points, lines or polygons

4
Q

LIST MAP MANIPULATIONS

A
ways to manipulate each map layers
Clip
Eliminate
Split
Dissolve
Append
5
Q

POLYGON OVERLAY

A

layers can be combined to produce new layers through geometric intersections

find polygons formed by the intersection of two (or more) polygons

a layer produced by an overlay will contain both the spatial data and attribute data of the input layers

can overlay points, lines or polygons

6
Q

Spatial data query methods

A

Structured Query Language (SQL)

used to query the map layer
results can be mapped or presented in a conventional data table and / or directly in the map
useful to produce maps with subsets of the data (filters) or by theme/interest

7
Q

Spatial data query method

A

Structured Query Language (SQL)

code language used to query the map layer
results can be mapped or presented in a conventional data table and / or directly in the map
useful to produce maps with subsets of the data (filters) or by theme/interest

8
Q

Uses for buffering

A

sphere/zone of influence of a geographic object

zone of protection (which keeps undesirable geographic objects away from other objects)

9
Q

Clip

A

extracts input features contained within a clip feature

basically clip a study region to certain shape

10
Q

Clip

A

extracts input features contained within a clip feature

basically clip a study region to certain shape, doesn’t change the information inside

11
Q

Split

A

split layer into multiple new layers based on smaller areas/zones

not common to use

12
Q

Dissolve

A

aggregate smaller zonal units into larger zonal units based on a specific common attribute, type of generalisation

careful about spatial analysis due to modifiable unit problem

13
Q

Append

A

merge multiple map layers at edges into one bigger new layer

opposite of split

14
Q

Polygon overlay methods

A

if the input map has a different area extent that the overlay map, then the extent of the output may vary depending on the overlay method used

three common methods:
Union
Intersect
Identify

15
Q

Union overlay

A

preserves all map features from the input and the overlay maps

adding layers together with different extents, but retain all features of both

16
Q

Intersect overlay

A

intersect method preserves only the area common to the two input themes in the output

17
Q

Identity overlay

A

identity preserves only map features that fall within the area extent defined by the input map