1. Vector Analysis
Ming-Chun Lee

2. Spatial Analysis
What is Spatial Analysis?
Spatial analysis is a set of methods whose results change when the locations of the objects being analyzed change.
Turning raw data into useful information
Reveal things that might otherwise be invisible
What is Spatial Analysis?
Spatial analysis is a set of methods whose results change when the locations of the objects being analyzed change.
Emphasis spatial analysis is about spatial data
Location-sensitive
Select by location, location changes definitely change the selection result
Select by attribute, location changes, the distribution of the selection result may also change..
For example: select bus route passing through downtown, but some of bus routes may be moved, then your selection result chnage
Turning raw data into useful information
Reveal things that might otherwise be invisible, or say incomprehensible

3. Spatial Analysis Turning raw data into useful information
Extracting or creating new information about a set of geographic features and examining the relationships between them.
The set of geographic features used in spatial analysis could pertain to data within only one layer or within two or more layers depending upon the users needs.
Turning raw data into useful information
Extracting or creating new information about a set of geographic features and examining the relationships between them.
The set of geographic features used in spatial analysis could pertain to data within only one layer or within 2 or more layers depending upon the users needs.
Last week, we looked at how you can select data, by location or by attributes, how you can re-classify a dataset, those are all applied to a single dataset.
today, we will look at some other tools allow you to do spatial analysis on multiple layers..

4. Spatial Analysis Methods range from simple to sophisticated
Usually involves manipulations or calculation of coordinates or attribute variables with a various operators (tools), such as:
Selection
Measuring
Reclassification
Dissolving
Overlay
Buffering
Methods range from simple to sophisticated
Usually involves manipulations or calculation of coordinates or attribute variables with a various operators (tools), such as:
Selection
Measuring
Reclassification
Dissolving
Overlay
Buffering

5. Selection Can be invoked on spatial and attribute components
Selection by Attributes
Selection by Locations
Involves selective search
No new objects created
example: lots owned by foreigners (attribute)
example: lots along the substation buffer (location)
Can be invoked on spatial and attribute components
Selection by Attributes
Selection by Locations
Involves selective search - data query
No new objects created
example: lots owned by foreigners (attribute)
example: lots along the substation buffer (location)

6. Measurements Getting numerical values that describe aspect of data
Length
Area
Many tasks require measurement from maps
measurement of distance between two points
measurement of area, e.g. the area of a parcel of land
Getting numerical values that describe aspect of data
Length
Area
Many tasks require measurement from maps
measurement of distance between two points
measurement of area, e.g. the area of a parcel of land

7. Reclassification
Classification - identify a set of characteristics to group together objects.
In a vector system, classification involves addition of objects characteristics. (join a table)
In a raster system, classification involves converting or coding cell values.
Classification examples: Land parcels for housing are classed into single-family and multi-family
Classification provides new patterns/relationships
Classification - identify a set of characteristics to group together objects.
In a vector system, classification involves addition of objects characteristics. (join a table), base on additional information
In a raster system, classification involves converting or coding cell values.
Classification examples: Land parcels for housing are classed into single-family and multi-family
Classification provides new patterns/relationships
Reclassification does not create new dataset, just provide new information

8. ORIGINAL CLASSIFICATION GENERALIZED CLASSIFICATION
Reclassification
URBAN
RESIDENTIAL
INDUSTRIAL
RURAL
FOREST
AGRICULTURE
ORIGINAL CLASSIFICATION
GENERALIZED CLASSIFICATION
The way we look at the dataset different

9. Overlay Analysis Combination of different data layers
Both spatial and attribute data is combined
Produces new layers
Involves two or more data layers
You can only overlay or analyze two themes
But you can combine two into one and then deal with the third one and so one; input theme can be point/line/polygon, but overlay needs to be a polygon
All themes need to be spatially registered
Need to have same coordinate system
Combination of different data layers
Both spatial and attribute data is combined
Produces new layers
Involves two or more data layers
You can only overlay or analyze two themes
But you can combine two into one and then deal with the third one and so one;
input theme can be point/line/polygon, but overlay needs to be a polygon
All themes need to be spatially registered
Need to have same coordinate system

10. Overlay Analysis Until the arrival of GIS
Map overlay analysis was performed manually
Superimposing transparent map layers on a light table to identify sites simultaneously meeting a number of criteria
Overlay operations can be performed in vector/ raster-based GIS
Overlay operation is a key analytical capability of a GIS
New data can be created by combining two or more input data
Overlay is a common means doing spatial analysis, even before GIS was invented…
Until the arrival of GIS
Map overlay analysis was performed manually
Superimposing transparent map layers on a light table to identify sites simultaneously meeting a number of criteria
Overlay operations can be performed in vector/ raster-based GIS
Overlay operation is a key analytical capability of a GIS
New data can be created by combining two or more input data

11. Overlay Analysis

12. Overlay Analysis

13. Vector vs. Raster Vector Overlay Raster Overlay
URBDP 498w - Introduction to GIS in Planning
Lecture 8

14. Vector Overlay Based on geometry and topology
Vector overlay operation results in a more complex output layer
More polygons / intersections / line segments than input layers
Calculates new topology and associated attributes
More time-consuming, complex and computationally expensive, in comparison with raster-based overlay operations
Based on geometry and topology
Vector overlay operation results in a more complex output layer
More polygons / intersections / line segments than input layers
Calculates new topology and associated attributes
More time-consuming, complex and computationally expensive, in comparison with raster-based overlay operations

15. Raster Overlay
Cell by cell process which results in the combination of the two input layers
known as map algebra
operations include boolean, multiply, and algebra
Cell by cell process which results in the combination of the two input layers
known as map algebra
operations include boolean, multiply, and algebra

16. Three Types of Vector Overlay
Point-in-Polygon
Points are assigned attribute of polygon
E.g. wildlife (point) and assoc. with vegetation (poly)
Line-in-polygon
Original lines are dissected by polygon boundary
Lines will have attribute of lines and polygons
E.g. roads and soil types along roads
Polygon-on-polygon
Each new polygon will have attribute from both
E.g. elevation and vegetation or elevation and rainfall
Point-in-Polygon
Points are assigned attribute of polygon
E.g. wildlife (point) and assoc. with vegetation (poly)
Line-in-polygon
Original lines are dissected by polygon boundary
Lines will have attribute of lines and polygons
E.g. roads and soil types along roads
Polygon-on-polygon
Each new polygon will have attribute from both
E.g. elevation and vegetation or elevation and rainfall

17. Boolean Logic Determines the binary properties of features
True-false, yes-no, or presence-absence
Rather than using numbers and magnitudes of features
Reduces measures to some binary condition
Simplifies the results of overlay operations
Determines the binary properties of features
True-false, yes-no, or presence-absence
Rather than using numbers and magnitudes of features
Reduces measures to some binary condition
Simplifies the results of overlay operations

18. Boolean Logic A NOT B A A&B B B NOT A Union (A or B)
Intersection (A & B)

19. Boolean Logic

20. Buffering
Common GIS operation
A type of proximity analysis where a buffer zone is created to perform a search
Buffer: encloses point, line, or polygon at specified distance.
Search: specify a distance from a point (radius), line (corridor), area (area)
New spatial objects created
Common GIS operation
A type of proximity analysis where a buffer zone is created to perform a search
Buffer: encloses point, line, or polygon at specified distance.
Search: specify a distance from a point (radius), line (corridor), area (area)
New spatial objects created

21. Buffer Generation Buffering a Point Buffering a Line Buffering an Area
All area within one mile of a city
Buffering a Line
All areas within 100 meters of a road
Buffering an Area
All areas within 500 meters of a wetlands area.
Buffering a Point
All area within one mile of a city
Buffering a Line
All areas within 100 meters of a road
Buffering an Area
All areas within 500 meters of a wetlands area.

22. Buffer Generation
Buffering possible with raster or vector data models

23. Vector Analysis Dissolve Overlays for Merging Diverse Layers
ArcToolbox Dissolve
Overlays for Merging Diverse Layers
UNION
INTERSECT
IDENTITY
Overlays for Trimming Diverse Layer Extents
CLIP
ERASE
Combining Similar Layers with Different Extents
MERGE
UPDATE
Creating Proximity- Based Polygon Layers: BUFFER
Dissolve
ArcMap Dissolve Regions
ArcToolbox Dissolve
Overlays for Merging Diverse Layers
UNION
INTERSECT
IDENTITY
Overlays for Trimming Diverse Layer Extents
CLIP
ERASE
Combining Similar Layers with Different Extents
MERGE
UPDATE
Creating Proximity-Based Polygon Layers: BUFFER

24. DISSOLVE ArcMap Merges Non- Adjacent Polygons GeoProcessing Wizard
Operates on Shapefiles, Coverages
Merges Non- Adjacent Polygons ID
Color A
Purple B C
Blue D
Green E A D C B E ID
Color A
Purple C
Blue D
Green D A C
ArcMap
GeoProcessing Wizard
Operates on Shapefiles, Coverages
Merges Non-Adjacent Polygons D

25. UNION Combine Only the Common Extents of Both Layers
Preserve All Attributes
Combine Only the Common Extents of Both Layers
Preserve All Attributes
URBDP 498w - Introduction to GIS in Planning
Lecture 8

26. INTERSECT Combine Full Extents of Both Layers Preserve All Attributes

27. IDENTITY Combine Only the Extents of the Original Layer
Preserve All Attributes
Combine Only the Extents of the Original Layer
Preserve All Attributes
URBDP 498w - Introduction to GIS in Planning
Lecture 8

28. CLIP Trim the Original Layer to Only the Extents of the Clip Layer
Preserve Only the Original Layer’s Attributes
Trim the Original Layer to Only the Extents of the Clip Layer
Preserve Only the Original Layer’s Attributes
URBDP 498w - Introduction to GIS in Planning
Lecture 8

29. ERASE Trim the Original Layer to Exclude the Extents of the Clip Layer
Preserve Only the Original Layer’s Attributes
Trim the Original Layer to Exclude the Extents of the Clip Layer
Preserve Only the Original Layer’s Attributes
URBDP 498w - Introduction to GIS in Planning
Lecture 8

30. MERGE/APPEND Add Non-Overlapping Extents of Multiple Layers
Preserve Consistent Attributes
Add Non-Overlapping Extents of Multiple Layers
Preserve Consistent Attributes

31. UPDATE Add Overlapping Extents of Multiple Layers
Preserve Consistent Attributes
Within Shared Extents, Give Preference to Newer Layer
Add Overlapping Extents of Multiple Layers
Preserve Consistent Attributes
Within Shared Extents, Give Preference to Newer Layer

32. Summary of Overlay Operations
Original Extents
Original Attributes
New Extents
New Attributes
UNION
Overlap
Different
Total
All
INTERSECT
Shared Only
IDENTITY
Layer A
CLIP
Layer B
ERASE
Layer A–B
MERGE
No Overlap
Same
UPDATE
All*
* Giving Preference to Layer B when A & B Conflict

33. BUFFER
Create a Polygon Layer with Boundaries at a Specified Distance from Another Layer
Fixed Distance
Variable Distance Based on an Attribute
Series of Buffers
Create a Polygon Layer with Boundaries at a Specified Distance from Another Layer
You can make a buffer surround a point, a line, or another polygon..
Three different ways you can specify the distance for a buffer:
Fixed Distance
Variable Distance Based on an Attribute
Series of Buffers

34. BUFFER Fixed Distance Examples: Walking Distance to Bus Stops
Areas of Street Light Illumination

35. BUFFER Examples: Noise Levels By Street Type
Variable Distance Based on an Attribute
Examples:
Noise Levels By Street Type

36. BUFFER Examples: Walking Distance to Bus Stops
Series of Buffers
Examples:
Walking Distance to Bus Stops
Areas of Street Light Illumination

37. Tools for Spatial Analysis
All of these tools are found in ArcToolbox in ArcMap

38. Example of Vector-Based Analysis
Find suitable sites for a new arboretum
Site Criteria:
Within county limit
Deep, Fertile, Loamy Soils
Forested Land
More than 1 km from major rivers
Between 2 and 4 kms from major roads

39. County Boundary

40. Major Roads Clipped to County

41. Major Rivers Clipped to County

42. Buffer Rings on Roads 2-4 km

43. Buffer of Roads >2km <4km

44. Land Use

45. Forest Land Cover

46. Clip Forest LC to Roads

47. County Soils

48. Deep, Fertile, Loamy Soils

49. Clip Soils to Roads

50. Intersect Soils and LC

51. Select SOIL/LC within 1km of Rivers

52. Switch Selection

53. Site Selections