Lecture 5

Question 1

What does spatial mean?

Answer 1

Where

Question 2

What does thematic mean?

Answer 2

What

Question 3

What does temporal mean?

Answer 3

When

Question 4

What are the transformation stages within GIS?

Answer 4

Real World -> Raw Data (data collection)

• > Data model (data manipulation)
• > Output data

Question 5

Primary data capture

Raster

Answer 5

Remotely sensed data
Satellite imagery
Aerial photography
Wireless sensors

Question 6

Primary data capture

Vector

Answer 6

Land Surveys

Global positioning systems (GPS)

Question 7

Secondary data capture

Raster

Answer 7

Scanning

Question 8

Secondary data capture

Vector

Answer 8

Digitising

Question 9

What is Aerial photography?

Answer 9

Snapshot of earth at a particular time
Cameras mounted in airplanes flying at low altitude
Useful for background/context or can be transformed into actual objects

Question 10

Advantages of aerial photography

Answer 10

Widely available
Cheaper than satellite images
Good for monitoring change/ sequence of events
Goof for large scale, small area projects
High spectral, spatial and temporal resolution
Can create 3D images by overlapping images

Question 11

Disadvantages of aerial photography

Answer 11

Not spatially referenced – have to be geo-referenced
Scale distortion – have to be geo-rectified
Susceptible to daily/seasonal/annual changes in features

Question 12

Primary data capture

Land Surveys

Answer 12

Primary vector data capture
Measures angle and distance from known points to establish 3-D location
Increasingly automated
Time-consuming & expensive but accurate

Question 13

Secondary data capture

Digitising

Answer 13

• Manual digitising
• Table digitiser & PC or on-screen
• Registration/TIC points
• Point & stream modes
• Time-consuming
• Requires extensive editing, cleaning & error-checking

Question 14

Digitising errors depend on

Answer 14

• Scale & resolution of source map
• Quality of equipment/software
• Skill/experience of operator
• Quality of editing process

Question 15

Data conversion

•Change in data model:

Answer 15

–Raster to vector: vectorisation

–Vector to raster: rasterisation

Question 16

Data conversion

•Change in feature type:

Answer 16

–Points to areas: aggregation

Question 17

Data storage: databases

Databases important in GIS to store, organise, analyse and retrieve data

Answer 17

Tables
Columns – attributes to be stored (fields)
Rows – values of attributes for each spatial feature
Keys – the field/attribute used to uniquely identify each feature, often used to join tables
Relations – relationships/links between tables/records

Question 18

What is Structured Query Language (SQL)?

Answer 18

• Standard language for querying databases

* Sets of logical expressions

Question 19

Structured Query Language (SQL)

Pseudo-English-language style

Answer 19

–Select land plots where owner = ‘Smith’
–Select hotels where street name like ‘High St.’ and rooms > 40
–Order by population
–Update table set population density = population / area
–Mathematical expressions: exp(), log(), sqr()
–Relational joins
•Many are now menu/wizard based e.g. MS Access

Question 20

What are spatial queries?

Answer 20

…where?
Which towns are within 5 miles of Happy Valley?
Aspatial queries … what?
How many days in the year had a temperature below 0 ºC?
GIS queries usually combine elements
of both spatial and aspatial queries

Question 21

Identify the spatial and aspatial parts of this query…

Which five-star hotels are within 5 miles of the University?

Answer 21

Which five-star hotels (aspatial)

are

within 5 miles of the University? (spatial)

Question 22

Identify the spatial and aspatial parts of this query…

What is the shortest route from Southampton to London, without using any motorways?

Answer 22

What is the

shortest route from Southampton to London, (spatial)

without using any motorways? (aspatial)

Question 23

Identify the spatial and aspatial parts of this query…

Which towns fall within land which is designated as National Park?

Answer 23

Which towns fall within land (spatial)

which is

designated as National Park? (aspatial)