GEOG 328 Final Unit / Exam Prep

Question 1

What is a Binary model? What is it most commonly used for?

Answer 1

A Binary model is a model which presents explicit data, generally does not include a suitability scale but rather denotes suitable/unsuitable.

Uses a Boolean output 1 (yes, suitable) or 0 (no, unsuitable)

Binary modelling is generally used for when criteria must absolutely be met.
Commonly used for siting analysis
Example: siting a new school

Question 2

What does Map calibration consist of for multi-criteria modelling

Answer 2

Binary - apply thresholds: exclude (0), include (1)

Multiple categories - Apply thresholds: high, medium, low (figure out levels of acceptance)
Range from 0-1 (or 100) - Linear / function

Question 3

What does layer combination mean with regards to Multi-criteria modelling?

Answer 3

Combining the quantitative variables into one layer

Question 4

What does Weighted Criteria Mean with regards to Multi-criteria Modelling?

Answer 4

The process whereby each input can be weighted according to its importance or its percent influence.

Question 5

What does “constrain” refer to with regards to multi-criteria modelling?

Answer 5

It removes areas that should be excluded - keeps the output from looking strange.

e.g. Beetle infestations don’t occur in water/human illness does not occur where population density is 0.

Question 6

What is a model?

Answer 6

A model is a representation of the real world.

Question 7

What is a Spatial Model?

Answer 7

A spatial model is a representation of some phenomena and incorporates spatial data and relationships

Question 8

What steps do you need to do before modelling?

Answer 8

Before modelling, data must be calibrated, layers of data integrated and logical/spatial constraints applied.

Question 9

Before performing multi-criteria spatial modelling what must be done with the data?

Answer 9

For multi-criteria spatial modelling the data must be calibrated, layered, and constrained to aid in guiding the problem solving and analysis.

Question 10

What is terrain?

Answer 10

Terrain - Also know as “relief”, this is the third dimension (elevation) of the land surface. The “lie of the land”.

Question 11

How is terrain Expressed?

Answer 11

Expressed as elevation, slope, and aspect.

Question 12

What does Terrain influence?

Answer 12

Influences climate, water, and water flow.

Question 13

What is Bathymetry?

Answer 13

Underwater terrain.

Question 14

How is Digital terrain surface modelling achieved?

Answer 14

Elevation points are used to create models of terrain.

Question 15

T?F - Both DEM and TIN (triangulated irregular network) are considered to be digital elevation models?

Answer 15

TRUE

Question 16

Of DEM and Tin, Which is a Raster and which a Vector?

Answer 16

DEM is used to refer to raster models.

Tin is used to refer to vector models.

Question 17

What are some methods for obtaining elevation data to create DEM’s

Answer 17

Lidar-light detecting and ranging
Stereo photogrammetry from aerial surveys
Multi-view stereo applied to aerial photography.
Interferometry from radar data.
Real time kinematic gps
Topographic maps
Theodolite or total station
Doppler radar
Surveying and mapping drones range imaging.

Question 18

What are some problems with Ground survey and GPS?

Answer 18

It is - expensive, time consuming, not viable over large areas

Question 19

Problems with Stereo photogrammetry?

Answer 19

Problems due to tree cover / land cover and it is very time-consuming.

Question 20

What are some pros and cons of LiDAR?

Answer 20

Pros: Post-processing results in raster surface / Gives you millions of points of data / It can map bare earth even with vegetation.

Cons: Very Very expensive and time-consuming in post processing.

Question 21

Pro’s and Con’s of Modern Photogrammetry?

Answer 21

Pros: Advances in computing power, software and drones / Less expensive than LiDar / accuracy ~5cm possible / Results in both DEM and ocular imagery, so good for visualization

Cons: Does not do will with vegetation (>60%)

Question 22

What are some benefits of using InSAR to map DEMs (satellite)

Answer 22

Generate high quality DEM models and measurements of displacement (by comparing two images). Not affected by weather. effective for mapping large area’s

Question 23

How do you get collected data points to become surfaces?

Answer 23

Input points, whether collected by survey, photographs, LiDAR, ect, must be processed to create terrain models. Some require extensive post-structuring such as LiDAR.

The points are interpolated to create a surface with raster models (DEM), and triangulated to create vector models (TIN).

Question 24

Of Tin and DEM, which represents Gradual changes and which Abrupt?

Answer 24

Tin = Abrupt (creates a surface of triangles between collected data points and thus has the ability to represent sharp changes in values like cliffs)

DEM = Gradual (interpolated surface using all of the collected points, creates a gradual surface between values)

Question 25

What are the two types of DEM?

Answer 25

DTM (digital terrain model) a bare earth model.

DSM (digital surface model) = DTM + human made elements (buildings, roads) or natural features that are on the bare earth (Such as vegetation).

Question 26

What are Breaklines? Why are they important?

Answer 26

features on the landscape that act as discontinuities: they interrupt the surface.

important to try to help increase the accuracy of your in your interpolation. If you have an understanding of terrain and features you can include coordinates of lines or features that discounts data outside of those boundaries

Question 27

In what situation would you choose to use a TIN model? When would you use a DEM model?

Answer 27

TIN’s are generally used in smaller areas and are great with a good point cloud, they can also better represent complex terrain features. Processing time is longer + data storage is greater.

DEM (because of generalization) complex features are often smoothed out as a result. they can also include redundancy data. More visually appealing and widely used in GIS.

Question 28

How are Slope / Aspect / Ruggedness determined?

Answer 28

All three are derived using a neighbourhood analysis (looking at the input cell and the differences in the cells surrounding it)

Question 29

What is a Watershed?

Answer 29

How water is forced to move at the surface through an area as a result of the elevation.

Question 30

What are some applications of TSA applied within hydrological Modelling?

Answer 30

Sample applications: 
Flood management (climate change)
Watershed delineation
Stream delineation 
Stream networks

Question 31

What are the steps to delineate a Watershed?

Answer 31

1. Fill DEM (raster processing / pixel resolution / rounding (interpolating) can result in depressions (sinks, which are low points with no output.) Removing sinks is called “hydrological conditioning”
2. Flow direction Raster. Shows the direction that water will flow out of each cell. Uses a neighbourhood analysis to code and shows direction based on elevation/slope/aspect (like a backlink except not based on cost surface)
3. Specify pour points (essentially start point in cost distance) cells with high accumulated flow become points - everything upstream will become a watershed.
4. Delineate watersheds (use flow direction raster and pour raster as imputs)

Question 32

What was the goal of Alex Lausanne’s project?

Answer 32

To use suitability analysis to find potential archeological dig sites.

here she could use GIS tools to answer Archaeological problems.

End goal was to create a step by step guide to locate sites within a given time frame.

Question 33

What types of models did Alex Lausanne’s use to try and validate her study?

Answer 33

She first used a weighted variable model to find the highest areas of potential archaeological discoveries based on all of the sites variables. The model was also deductive (as no training data was available).

second was a decision tree to try modelling the predictive modelling. (No good)

Final model was binary decision tree (each cell went through the process and had to answer yes to each of the variables, then they would be considered high archeological potential)

Question 34

What was the result of Alex Lausanne’s study?

Answer 34

The result was a study area 23% of its original size with a roughly 80% discovery rate of archaeological finds as a result of two surveys undertaken.

Question 35

Alex Lausanne describes what a model is in her presentation. what was that?

Answer 35

A model is a representation of reality that must be interpreted by an informed researcher.