Week 6- Vector Analysis

Question 1

Vector data operations

Answer 1

1. Data transformation/projection
2. Attribute query
3. Classification and generalisation –
   reclassify, merge/split, dissolve
4. Measurement functions
5. Map overlay
6. Proximity analysis

Question 2

Data involved in GIS Analysis

Answer 2

1) Single data layer (Interpolation of point
data into contour lines)
2) Map pair (Clipping (“cookie cutter”) of one map by another map)

Question 3

1. Data transformation/projection

Answer 3

• Coordinate transformation –e.g. scale, orientation, shift

* Map projection –e.g. UTM to AMG

Question 4

2. Attribute Query

Answer 4

SQL to select objects

that are of interest and produce maps

Question 5

Kind of Joins:

Answer 5

Match – only include matched items only
All – allow combinations where no match
found, i.e. leaves blank fields

Question 6

logical operators ___ multiple attributes

Answer 6

combine

Question 7

Reclassify

Answer 7

areas by a single attribute or some combination

Question 8

3. Reclassify, merge/split and dissolve

Answer 8

• to group features
• to identify trends / clustering
• to simplify information

Question 9

Merge

Answer 9

polygons into large objects by recording the sequence of line segments that connect to form the boundary and assigning new ID numbers to each new object. Split is opposite to merge.

Question 10

Dissolve

Answer 10

dissolve boundaries between areas of same type (i.e if an attribute is similar in both polygons)

Question 11

Aggregation operation

Answer 11

• dissolve (spatial summary)

- Table summary: Simplify and summarise data to reveal overall trend (e.g region sum of housing approvals)

Question 12

Dissolve

Answer 12

Spatial aggregation (same as table summary though visual (geometry is merged))

Question 13

Data disaggregation operation

Answer 13

split:
- divide data to analyse data relationships
-integrate data
(e.g. Number of people renting by age intervals derived from separate data on
peoples age and dwelling ownership status)

Question 14

4. Measurement Functions

Answer 14

distances between two points
• lengths of lines or strings
• areas of polygons
• perimeters of polygons
• area of a single or group of classes
• volumes of cut and fill
• slope and aspect
• angles or directions of features; and
• cross-sections

Question 15

5. Overlay Functions (+draw)

Answer 15

Overlay analysis:

• all layers to be registered to same coordinate system
• Intersection (overlapping area of combined attributes)
• Union (boolean OR operation- keeps areas from both data layers)
• clip (cookie cuts)
• Update (feature replaces overlapping areas)
• Identity

Question 16

spatial join

Answer 16

• relate features based on spatial relationships:

- intersect, contains, distances within

Question 17

Overlay analysis Limitations

Answer 17

• ecological fallacy: assuming 50/50 population if you evenly split QLD in half
• sliver polygons (different versions of boundaries creating over or under shoots)

Question 18

6. Proximity Analysis

Answer 18

-to highlight or determine areas of influence of certain
features or phenomena (e.g How many X features are within 5km of feature Y)
–>buffering: (polygon or a region
created around a point, line or area)
–> nearest function