Spatial Analysis w2012

7/30/2019 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

3

3

2 2 3

2 1

2 1

3

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

3

3

2 2 3

2 1

2 1

3

1

2 2 1

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

Spatial Analysis w2012

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