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GIS Lectures > Module Review > Flashcards

Module Review Flashcards

1
Q

What are the 6 core components of a GIS?

A
  1. Network
  2. Software
  3. Data
  4. Procedures
  5. Hardware
  6. People
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2
Q

How can you define GIS?

A

“a system for capturing, storing, checking, integrating, manipulating , analysing and displaying spatial data from the real world for a particular set of purposes.”

“a set of tools for collecting, storing, retrieving at will, transforming, and displaying spatial data from the real world for a particular set of purposes.”

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3
Q

3 types of GIS systems

A

GIS
GIScience
GIStudies

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4
Q

What is spatial data?

A

Data that defines something about a location.
Location = where?
Attribute - what?

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5
Q

What is vector data?

A

A representation of the world using points, lines, and polygons.
Vector models are useful for storing data that has discrete boundaries, such as country borders, land parcels, and streets.

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6
Q

What are attributes?

A

A database or table linked to each vector feature

Can contain only an identifier or a large amount of additional data

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7
Q

What are spatial queries?

A 
What is at A?
A can be 
- A single feature 
- Features defined by distance 
- Features within areas
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8
Q

What are attribute (aspatial) queries?

A

Where is B true?
Query attribute data
- Structured query language
- Raster attribute table can be called reclassification
- Create new raster data set from results

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9
Q

What is topology?

A

Looks at geometric characteristics and relationships.

  • connectivity
  • adjacency
  • containment
  • distance
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10
Q

What is raster data?

A

Useful for continuous data

A grid of pixels or cells where each cell has a single numeric value.

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11
Q

What is the resolution of raster data?

A

refers to the area/ size of the cell/pixel

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12
Q

Examples of raster data?

A

Scanned maps
Aerial photography
Surfaces (elevation, house prices)

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13
Q

Raster precision/ resolution

Higher precision =

A

…smaller cell size
More cells required for same coverage
More detail
More processing power

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14
Q

What are data layers?

A

Each layer references a dataset and specifies how that dataset is portrayed using symbols and text labels.
Location and attribute
Layers can be combined visually
Information can be extracted from attributes based on location

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15
Q

What are map projections?

Why?

A

Method to represent the surface of the earth.

Creates maps and enables easier measurement

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16
Q

Different types of map projections?

A

Cylindrical
Azimuthal
Conic

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17
Q

What is a tangent projection?

A

A projection whose surface touches the globe’s without piercing it.
At the point or line of tangency, the projection is free from distortion.

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18
Q

What is a secant projection?

A

Two lines of minimal distortion creating parallel secant lines.

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19
Q

Why is there no distortion in tangent/secant projections?

A

Scale at tangent and secant lines.

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20
Q

What is a transverse mercator?

A

Transverse cylindrical projection.
Distances are only true along the central meridian
Accuracy reasonable within 15 degrees of the meridian
Used for national to large scale mapping.

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21
Q

Spatial referencing

Geographic co-ordinate systems

A

Latitude and longitude

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22
Q

Spatial referencing

Cartesian co-ordinate systems

A

OS National grid

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23
Q

Spatial referencing

Geocodes

A

Postcodes (descriptive/ text location)

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24
Q

Raster symbology

A

Interval and ratio data
Colours/ shading = progression
Reinforced with legend

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25
Q

Two main types of map

A

Topographic- reference maps with lots of different types of information
Thematic- relates to a topic e.g crime

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26
Q

Representations of spatial data

A

3D visualisation
Cartograms
Schematics

27
Q

Key elements of a map output

A 
Reference grid 
Map body 
Title 
North arrow
Legend
Scale 
Inset map
Map metadata
Copyright acknowledgment
28
Q

Large scale features

A

Covers small areas
Large amount of detail
1:1000
1:25000

29
Q

Small scale features

A

Covers large areas
Small amount of detail
1:250,000
1:1,000,000

30
Q

Types of scale

A

Ratio: Units do not matter as long as they are the same
Verbal (nominal): 1 cm = 1 km
Graphical

31
Q

Types of generalsiation

A 
Simplification 
Enlargement 
Displacement 
Combination
Selection (elimination) 
Classification
32
Q

Measurement of length

A

Pythagorean
Great circle
Manhatten

33
Q

What is the pythagorean measurement of length?

A

Straight line (euclidean) distance between two points on a flat plane

34
Q

What is the great circle measurement of length?

A

Gives the shortest distance between two points on a spherical globe given their latitudes and longitudes

35
Q

What is the manhattan measurement of length?

A

Linked to raster data

The sum of horizontal and vertical components when measuring a diagonal.

36
Q

What is an issue with vector length measurement?

A

Length of a true curve us almost always longer than length of poly line.

37
Q

What is the raster measurement of area?

A

Area = no of cells x cells area

38
Q

What is an example of a vector measurement?

A

Buffers

39
Q

What is an example of a raster measurement?

A

Euclidean distance

Each cell gives a distance to the closest source cell.

40
Q

What is reclassification?

A

Creation of new output later based on values in input layer.

Input: may be categorical or continuous
Output: Generally categorised

41
Q

How to to reclassify something.

A

Spatial analyst > reclass > reclassify

42
Q

Vector overlay

A

Comparison of layers which occupy same space
Select by locations (select features)
Used to create new data (geoprocessing tools)

43
Q

Types of vector overlay

A

Clip
Intersect
Union

44
Q

Basic cartographic modelling

Simple case

A

Input layer -> Single operation -> output

45
Q

Basic cartographic modelling

Complex case

A

Multiple input layers -> multiple operations -> output

46
Q

Data conversion

Raster to vector:

A

Vectorisation

47
Q

Data conversion

Vector to raster:

A

Rasterisation

48
Q

Data conversion

Change in feature type:

A

Points to area: Aggregation

49
Q

Why are data storage: data base important?

A

For storing, organising, analysing and retrieving data

50
Q

Types of data errors

A

Positional accuracy (precision- probable location e.g +/- 5m)
Attribute accuracy
Representations of reality

51
Q

Errors in data collection

A 
Sampling mistakes (technical difficulties, incorrect operation recording)
Sampling bias
52
Q

Remote sensing

Shadow =

A

Cloud distortion

53
Q

Accuracy

A

The extent to which an estimated data value represents its true value
Consists of two components:
Precision
Unbiasedness

54
Q

Precision

A

Specificity (e.g number of decimal places or significant features)
The dispersion of a measured or predicted value

55
Q

Bias

A

Any systematic difference between the true value and the measured or predicted value.

56
Q

Three key types of accuracy in GIS

A

Positional
Attribute
Topological

57
Q

What is positional accuracy?

A

Are features in the right place?

58
Q

What is attribute accuracy?

A

Do features have the correct value (continuous/ categorical)

59
Q

Benefits of GIS

Direct

A

Savings
Increased effectiveness
Brand new products

60
Q

Benefits of GIS

Indirect

A

Improved information sharing
Greater understanding
Better justification
More competitive

61
Q

Costs

Direct

A

Hardware/software
Data
Human and administrative costs

62
Q

Costs

Indirect

A

Increased reliance on computers

Higher skilled workforce required

63
Q

What is ecological fallacy?

A

Falsely attributing characteristics of a zone to individuals on the basis of their membership to that zone
Very common problem in the social sciences
Can lead to wrong conclusions about causality

64
Q

Geovisualisation

A

What3words
Traditional maps- limitations
Cartograms
Other visualisations

GIS Lectures (10 decks)

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