Spatial Analysis w2012
Transcript of Spatial Analysis w2012
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Border around
project area
Everything else
is hardly
noticeable but
its there
Big circles
and semi-
transparent
Color
distinction is
clear
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Introduction to GIS Yoh Kawano
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Spatial analysis refers to theformal techniques to conductanalysis using theirtopological, geometric, orgeographic properties.
In a narrower sense, spatial
analysis is the process ofanalyzing geographic data.
Types of spatial analysis youhave already been doing:
Buffering Select by location
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Layers can be
overlaid - placed
one over the other
based on a shared
geographic
reference
allowsanalysis of the
relationships
between layers
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Raster analysis is one method of Spatial Analysis.
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Why do we have to use raster data?
Vector data (points, lines and polygons) are limited to only certainspatial analyses
+ Point in polygon (which points are within
+ Line intersections
Vector data only knows about the space it occupies
Raster data covers the entire region Provides a more powerful format for advanced
spatial and statistical analysis
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A matrix of cells
Rows and columns(grid)
Examples: aerial
photographs, digitalphotos, scannedmaps
Examples in spatial
analyst
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As basemaps
As surface maps
As thematic maps
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Grid size is defined by extent, spacing and no
data value information Number of rows, number of column
Cell sizes (X and Y)
Top, left , bottom and right coordinates
Grid values Real (floating decimal point)
Integer (may have associated attribute table)
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Numberof
rows
Number of Columns
(X,Y)
Cell size
NODATA cell
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derive new information from your existing data, analyze spatial relationships,
build spatial models, and
perform complex raster operations.
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Find suitable locations
Model and visualize crimepatterns
Analyze transportationcorridors
Perform land use analysis
Conduct risk assessments
Predict fire risk Determine erosion potential
Determine pollution levels
Perform crop yield analysis
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Step 1: State the Problem Find the most suitable location for a new long-term care facility in Long
Beach
Step 2: Identify the Parameters and Weight Supply: needs to be far from existing facilities (weighted by number of
beds in the facilities) (25%)
Demand: number of persons over 65 (50%)
Access: close to major streets (25%)
Step 3: Prepare Your Input Datasets Long Beach Facilities (point) Census Tracts Age>65 (polygon)
Major Streets (line)
Step 4: Perform the Analysis
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ArcCatalog: Make sure all your layers are in the same projection (eg: UTM Zone 11N)
ArcMap:1. Load all your layers, double check that you are on the right projection
and units (eg: miles)
2. Turn on Spatial Analyst Toolbar
3. Set the Environment (very important, ensures that raster layers have
the same cell size!)4. Load your indicator layers
5. Rasterize your layers (Ex: Kernel Density, Feature to Raster, EuclideanDistance)
6. Reclassify
7. Apply weights
8. Generate final raster
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Step 1
Ensure that each layer in your
project has the SAME projection
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Step 2
Check the map units
*Even if you change the display units,spatial analysis will be conducted using
the map units
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Step 3
Access ArcToolbox Environments
Right click
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Step 4
Set the environment
1. Processing Extent
Usually set this to the
extent of your project,
or the largest layer
2. Raster Analysis
Cell size and Mask
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Best site for
new facility
Kernel
Density on
Number of
Beds
Feature to
Raster on
Age>65
Euclidean
Distance
Long Beach
Facilities
Long Beach
Census Tracts
Long Beach
Major Roads
Far from
existing
facilities
Close to areas
with high
numbers of
senior citizens
Close to major
streets
25% 50% 25%
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Spatial Analysis Tools > Density > Kernel Density
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Spatial Analysis Tools > Distance > Euclidean Distance
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Conversion Tools > To Raster > Feature to Raster
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Long Beach
Facilities
Long Beach
Census Tracts
Long Beach
Major Roads
Kernel
Density on
Number of
Beds
Feature to
Raster on
Age>65
Euclidean
Distance
Reclassify:
3 most desirable
1 = least desirable
Reclassify:
3 most desirable
1 = least desirable
Reclassify:
3 most desirable
1 = least desirable
3 3
1 3
3
2
1 1 2
1 1
1 2
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2 2 3
2 1
2 1
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1
2 2 1
Spatial Analysis Tools > Reclass > Reclassify
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3 3
1 3
3
2
1 1 2
1 1
1 2
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2 2 3
2 1
2 1
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Long Beach
Facilities
Long Beach
Census Tracts
Long Beach
Major Roads
.75 .75
.25 .75
.75
.5
.25 .25 .5
.5 .5
.5 1
1.5
1.5
1 1 1.5
.5 .25
.5 .25
.75
.25
.5 .5 .25
1.75 1.5
1.25 2
3
2.25
1.75 1.75 2.25
Spatial Analysis Tools > Map Algebra > Raster Calculator