Week 1-3: GIS concepts

Question 1

Types of GIS q’s + e.g’s

Answer 1

Location. Where is the nearest shop?
Patterns. Where do high concentrations of students live?
Trends. Where are glaciers retreating in the European Alps?
Conditions. Where is the flat land within 500 m of the highway?
Implications. If we build a theme park here, what will be the effect on traffic flows?

Question 2

Types of GIS architecture

Answer 2

1. Desktop (stand alone desktop with GIS files)
2. Centralised desktop (Desktop sharing files to other PC’s over LAN)
3. Client-server (data base to be accessed by PC’s only via WAN)
4. Centralised server
   - GIS app server accessable on PC’s Browsers, Devices, Web
   - For multinational companies

Question 3

continuous and discrete GIS data e.g

Answer 3

continuous: distance to classes
Discrete: bus timetable

Question 4

Data model simply is

Answer 4

-set of constructs for representing objects and processes (geographical features) in the digital environment of a computer

Question 5

Data model components

Answer 5

Reality–>Conceptual model (Partially structured model e.g buildings in a campus)–>Logical model (Diagrams and lists e.g buildings connected to roads)–>Physical model (GIS representation: tables with compiled data, legend)

Increasing level of abstraction from human orientated to computer orientated.

Question 6

Digital ELevation model is ___ data

Answer 6

contin

Question 7

watersheds, streams and waterbodies are ____ data

Answer 7

discrete

Question 8

Raster data is most useful for representing:

Answer 8

continuous fields:

e.g elevation, temperature, soil type, land use

Question 9

Vector data is most useful for representing

Answer 9

discrete objects:

e.g property lines, political boundaries, transportation.

Question 10

Vector data models consist of ___, ___ and ___

Answer 10

Points, lines and polygons (shape files)

Question 11

raster data model is based on ___

Answer 11

a grid of cells

cells values are represented as numbers in a database, each number defining a land use (for e.g).

Question 12

Attribute data

Answer 12

-link spatial attributes with thematic attributes (non-spatial)

Question 13

Vector is more accurate than raster T/F?

Answer 13

True

- raster cell size is bigger than exact vector location

Question 14

e.g raster data sources

Answer 14

-remote sensing (LANDSAT, SPOT), scanned maps, DEM

Question 15

e.g vector data sources

Answer 15

• census data (tabular)

Question 16

does changing raster to vector data increase accuracy?

Answer 16

no because it the vector is simply joining the center of each cell.

Question 17

Modifiable Areal Unit Problem (MAUP)

Answer 17

• Effect of geographic unit size and shape on geographic patterns:
  1. Scale effect
  2. Zoning effect

Question 18

Three elements of topology

Answer 18

Adjacency, connectivity and containment (enclosure)

Question 19

Adjacency

Answer 19

when two polygons share the same boundary

Question 20

Connectivity

Answer 20

multiple lines are connected at one point (node)

Question 21

Containment

Answer 21

one polygon contained within another poligon

Question 22

Geographic coordinate systems

Answer 22

• defines unique points on the earth’s surface
• Longitude and latitude
• referenced to a datum

Question 23

which type of latitude requires knowledge of the earth’s shape (ellipsoid)

Answer 23

Geodetic

standard ellipsoid datum: WGS84

Question 24

Projected coordinate systems

Answer 24

-transforms a 3D Geographic Coordinate System to a flat coordinate system

Question 25

Secondary data:

Answer 25

- OpenStreetMap - Digital globes (nearMap) - online datasets - Remote sensing (LiDAR)

Question 26

GIS question example: Nuclear Waste Disposal a) what data? b) where data (primary+secondary) c) Data model used and why

Answer 26

a) -geology of the region so that nuclear waste is not stored near potentially reactive materials or unstable rock types or near minerals that could potentially be mined in the future. - transportation routes: to identify where there is sufficient transport routes to waste site -population: ideal site should be away from pop. centres - conservation areas: top avoid -watershed: no radioactive waste to enter water course. b) roads-->openstreep map/AURIN population-->census conservation--> Qspatial geology--> qld gov primary data-insitu vector data capture--> chosen site measuring angles and dists. from known points c) Vector data analysis. Find intersection of suitability criteria i.e geology type, adequate trnasport infrastructure, outside conservation areas, away from pop.

Question 27

Primary Data

Answer 27

In-situ data capture - GPS - Ground Surveying ( - Location based service - Digitizing (on screen)

Question 28

Remote sensing- resolution

Answer 28

Spectral resolution

Question 29

Secondary vs primary data

Answer 29

- primary more expensive | - secondary is vast and readily available

Question 30

resolution in remote sensing

Answer 30

spectral resolution: colour spectrum spatial: size of each pixel corresponding to the real ground temporal resolution: intervals of scanning Radiometric resolution:

Question 31

types of transformation in georeferencing

Answer 31

-Affine: 3 points needed -second order polynomial: 6 points needed third order polynomial

Question 32

Root mean square error

Answer 32

assess "goodness-of-fit" to control points but NOT non-control point distrotion

Question 33

types of measurement errors

Answer 33

1. Positional accuracy 2. attribute accuracy 3. logical consistency 4. completeness

Question 34

positional accuracy

Answer 34

expected difference in the measured geographic location of an entity from its true ground position

Question 35

Absolute accuracy (within positional accuracy)

Answer 35

accuracy with respect to a coordinate system

Question 36

Relative accuracy (within position accuracy)

Answer 36

accuracy with respoect to position of geographic entities relative to each other

Question 37

attribute accuracy

Answer 37

of non-spatial attributes of geographic features (e.g land classification: grass where buildings are)

Question 38

logical consistency

Answer 38

faithfulness of the data structure. Spatial data inconsistencies: incorrect line intersection, duplicate lines or boundaries or gaps in lines.

Question 39

completeness

Answer 39

e.g holes in data, unclassified areas.

Question 40

metadata

Answer 40

data about data: -how, when, where and who collected data - scale of data - coordinate system - data quality and accuracy

Question 41

data quality: scale--> extent and resolution

Answer 41

extent is size of study area | resolution is size of geographical units (cell size)

Question 42

data sharing requirements

Answer 42

- strict metadata standards - standard data formats for transferability among platforms - data sharing agreements - portals for access and storage of data

Question 43

2 classes of GIS Questions

Answer 43

-Normative (practical or decision-making/design applications). e.g where to site a nuclear plant - Positive (Discovery or the Advancement of Science). e.g where is global warming impacting most