INTRODUCTION TO SPATIAL
ANALYSIS
Four fundamental functions of GIS fall
under the manipulation and analysis
component (Martin, 1991):
1.
2.
3.
4.
Reclassification operations
Overlay operations
Distance and connectivity measurements
Neighbourhood characterisation
Will be discussed in the next chapter.
1. Reclassification operations
• these transform the attribute information
associated with a single map coverage for
example a map of population densities may be
classified into classes such as 'sparsely
populated' or 'overcrowded' without reference to
other data.
• This function can also be used to calculate
densities of sales observations
Example: the
darker the more
dense the state
population
MAP
classification provides new patterns/relationships
URBAN
RESIDENTIAL
URBAN
INDUSTRIAL
RURAL
AGRICULTURE
RURAL
FOREST
ORIGINAL CLASSIFICATION
URBAN
RURAL
GENERALIZED CLASSIFICATION
Classification (cont.)
Classification:
• Land parcels for housing are classed into
• single storey terrace,
• double storey terrace and
• bungalow.
Generalisation:
• single storey terrace, double storey terrace
and bungalow are generalised under housing
lots
2. Overlay operations
• involve the combination of two or more maps
according to boolean conditions and may result
in the delineation of new boundaries of housing
market
An overlay of three layers of data
N
W
E
S
4
0
Ordnance Survey Crown Copyright. All rights reserved
4 Miles
Motorway12km.shp
Glasgow City Cou ncil - UKBORDERS.shp
Nb rMean of residuals - 500m.shp
-0.74 - -0.57 (greatest overestimation)
-0.57 - -0.35
-0.35 - 0
0
0 - 0.35
0.35 - 0.57
0.57 - 0.78 (greatest u nd erestimation)
No Data
3. Distance and connectivity
measurements
• include both simple measures of inter-point
distance and more complex operations such as
the construction of zones of increasing transport
cost away from specified locations.
• Distance measurement can be used to calculate
straight line and network distance.
• Includes perimeter and area measurements…
MEASUREMENT
DISTANCE
X
5 KM
Y
B
A
D
C
A- B = 20 = 40%
B- C = 20 = 40%
C - D= 10 = 20%
PARAMETER
AREA/SIZE
2
10 km
DISTANCE (STRAIGHT LINE) MEASUREMENT
A- B: Alor Setar - Kuala Lumpur
360 KM
B- C: Kuala Lumpur - Kuantan
270 KM
TOTAL: 630 KM
AREA MEASUREMENT
1765.635
1470.998
4. Neighbourhood characterisation
• involves ascribing values to location according
to characteristics of the surrounding region.
• Such operations may involve both summary and
mean measures of a variable.
• This can be used to examine positive and
negative spatial autocorrelation house price
hedonic models.
Neighbourhood analysis of mean selling prices
within certain distance of a house
N
E
W
S
4
Ordnance Survey Crown Copyright. All rights reserved
0
4 Miles
Moto rw ay12km.shp
Glasgo w City Cou ncil - UKBORDERS.shp
Mean sellin g price (£ p er sq km) .shp
20500 - 45939
45939 - 71377
71377 - 96816
96816 - 122255
122255 - 147694
147694 - 173132
173132 - 198571
198571 - 224010
224010 - 249449
No Data
Other View of GIS Functions
• Anselin (1998) proposes that GIS functions
can be classified as follows
– Selection
– Manipulation
– Exploration
– Confirmation
GIS functions
• Selection: involves boolean queries and spatial sampling. This
seems similar to the overlay operations function.
• Manipulation: may be based on attribute data, map data, or
integration of both, simultaneously. This means analysing data
in an integrated manner where various data as available in the
database can be combined in an analysis.
• Exploration: for investigation of spatial structure and
involves description and visualisation. This is relevant to
spatial autocorrelation analysis of hedonic models using geostatistical method
• Confirmation: for modelling spatial association and/or
autocorrelation. This is also more relevant to spatial
autocorrelation analysis using geostatistical method.
DATA RECALL
• can be invoke on spatial and attribute components
• involves selective search
• no new objects created
• example: lots owned by foreigners
• example: lots along the substation buffer
LOTS OWNED BY FOREIGNERS
CLASSIFICATION AND GENERALISATION
• classification - identify a set of characteristics to
group together objects.
• in a vector system, classification involves addition of
objects characteristics.
• in a raster system, classification involves converting
or coding cell values.
• classification examples: Land parcels for housing are
classed into single storey terras, double storey terras
and bungalow.
• classification provides new patterns/relationships
• generalisation: single storey terras, double storey
terras and bungalow are generalise under housing
lots
Housing Age
Legend
Before 1900
1901-1930
1931-1950
1951 to 1999
Map showing classification of buildings according to age
URBAN
RESIDENTIAL
URBAN
INDUSTRIAL
RURAL
AGRICULTURE
RURAL
FOREST
ORIGINAL CLASSIFICATION
URBAN
RURAL
GENERALIZED CLASSIFICATION
...
• vector data
– converting attribute values for polygon, line and
point
• raster data
– converting attribute values of group cell
MEASUREMENT
• measurement functions includes distance, parameter
and area
• example: land parcels larger than 5 hectares
• example: shortest distance from KLCC to Pudu bas
station
MEASUREMENT
DISTANCE
X
5 KM
Y
B
A
D
C
A- B = 20 = 40%
B- C = 20 = 40%
C - D= 10 = 20%
PARAMETER
AREA/SIZE
2
10 km
DISTANCE MEASUREMENT
A- B: Alor Setar - Kuala Lumpur
360 KM
B- C: Kuala Lumpur - Kuantan
270 KM
TOTAL: 630 KM
AREA MEASUREMENT
1765.635
1470.998
... MEASUREMENT
• vector data
– area and parameter is obtained from coordinates
of the polygon nodes
– distance is derived from coordinates of
starting/ending nodes
– is more accurate than raster data
SEARCHING
• determine values against target object according to a
neighbourhood characteristic
• three parameters need to be identified
– targets
– neighbourhood around the targets
– applied neighbourhood function for resultant
values
• example: total of households within 1 km of proposed
shopping mall
– target-shopping mall
– neighborhood-in the radius of 1 km
– function-total residential units
... SPATIAL SEARCH
• operated as additional points in polygon, line in
polygon and polygon in polygon
• vector data
– point, line or polygon analysed with
neighbourhood polygon using coordinate nodes
– involves complex calculation with overlapping and
out-of-boundary neighbourhood
• raster data
– perform as overlay operations
NEIGHBOURHOOD
• represents ‘distance’ between map features
• ‘distance’ unit can be in measurement units or other
units like travelling time, noise level, visibility distance
etc.
• requires 4 parameters
– target location - schools, highways, etc.
– ‘distance’ units - meter, dB, ppm, etc.
– function for calculation on distance, perimeter,
travel time
– location to be analysed
... NEIGHBOURHOOD
• used to generate buffer zones
• example: a 2km zone along a proposed transmission
line alignment; zones exceeds 50dB around the
airport
• neighbourhood is most often complex and involves
data from various layers. For example, more than
50dB from noisy roads AND more than 1km from
factories AND 15 minutes walking time AND ...
R
Buffering a Point
eg. All area within one mile of a city
Buffering a Line
eg. All areas within 100 meters
of a road
Buffering an Area
eg. All areas within 500 meters
of a wetlands area.
OVERLAY
• Involves two or more data layers
• Produces new layers
• Two types of overlay operation
– arithmetic overlay
– logical overlay
• Arithmetic overlay involves mathematics operation
such as addition, subtraction, multiplication, etc.
MAP ALGEBRA (MULTIPLICATION)
OVERLAY BY MULTIPLICATION
DISTRICT
CROP AREA
1
2
3
4
X
OVERLAY
1
=
B
B
1 2
3 4
OVERLAY BY MAXIMUM VALUE
3
3
4
0
1
0
2
4
6
+
4
5
4
2
5
1
2
5
1
=
4
5
4
3
5
4
RAINFALL :
RAINFALL:
RAINFALL:
1980
1981
1980 - 1981
4
5
6
... OVERLAY
• vector data are sometimes more efficient than raster
data if data are not dense.
– vector data - operation based on the selected data
only
– raster data - operation on all cells - even null
values
Soil Type
+
Crops Production
(tons/hec)
Overlay Analysis
Overlay Result
GIS Technology: Relationship between Land use and Crop
Productivity
Jalan Hamzah
Noise Zone Map
Jalan Datuk Malik
Jalan Raja Uda
Jalan Hamzah
Jalan Datuk Malik
Sewerage pond
Sewerage pond
Area Map For Areas Outside Sewerage Services
Pan Malaysian
Plastic
Jalan Hamzah
Jalan Datuk Malik
Jalan Raja Uda
Industrial Buffer Zone Map