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Geographic Information Systems (GIS)in Planning and Resource Management

ENVS 6189 3.0 - lecture 7

John Sorrell

York University. sorrell@yorku.ca

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Session PurposeSession Purpose::

To discuss raster-based GIS processing, analysis and cartographic modeling as they are typically used to support geographic inquiry.

GIS in Environmental Studies

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Spatial Analysis:Spatial Analysis:

• various integrated analysis procedures for attribute and spatial data are used;

• new data layers may be derived or transformed from spatial analysis procedures;

• factors for consideration generally include: size, distribution, pattern, contiguity, neighborhood, shape, scale and orientation.

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..the process of sorting, visualizing and testing spatial data to explore possible patterns or relationships.

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Characteristics of Characteristics of the Raster Data the Raster Data Model:Model:

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Raster layers

Raster map

Vector map

Actual terrain

forest

drainage

highway

relief

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Characteristics of Characteristics of the Raster Cell:the Raster Cell:

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Cell value

Spatialresolution

Coordinate Referenceof end of point

Coordinate Referenceof start of point

Different attributesstored in different layers

Pixel

Spatial unit

Column no.Row no.

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Data Processing Operations Data Processing Operations with the Raster Data Layers:with the Raster Data Layers:

Input functions – prepare and structure raster data (resampling, compilation and editing).

Analysis functions – extract spatial relationship implicit in the source layers (geometric, reclassification, overlays operations).

Output functions – publishes output to inform decision making (graphs, stats reports and maps).

GIS in Environmental Studies

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RasterRaster--based Data based Data Analysis:Analysis:

• Local Operations • Neighborhood (Focal) Operations• Extended (Zonal) Neighborhood Operations• Regional (Global) Operations

The defining criterion for the framework is based on the use of cell configuration to group raster-based operations into categories.

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Local Operations:Local Operations:ReclassReclass -- OverlayOverlay

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Changes the Z values of input layer on a cell by cell basis to derive new output layer.

(a) Binary masking

(b) Classification Reduction

(c) Classification ranking

(d) Changing measurement scalesNominal scale Ordinal scale

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Local Operations:Local Operations:ReclassReclass –– Overlay (logical)Overlay (logical)

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A and B A not B

A or B A Xor B

Logical overlay AND to find “A” and “7” in the input raster layer

A=1Other=0

7=1Other=0

Overlay bylogical AND

Output layer

Logical overlay look for specific condition to be true.

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Local Operations:Local Operations:ReclassReclass –– Overlay (arithmetic)Overlay (arithmetic)

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Arithmetic “MULTIPLICATION” overlay to convert DEM data from Feet to Meters

Scalar: a factor that yields an output equal to the input multiplied by a constant

Scalar layer

Arithmetic overlays use + - * / and assignment operators to derive a output layer.

DEM layer

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Neighborhood (focal) Operations :Neighborhood (focal) Operations :

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Value assigned to target cell in new layeris a function of neighboring cells.

Floating 3x3 cell window of input layer.

Input layer.

Output layer.

Some uses: - determining slope and aspect- spatial filtering (spectral editing)- simple point interpolation or smoothing

Adjacent cells determine (z) value assigned to target cell.

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Extended (Zonal) Neighborhood Extended (Zonal) Neighborhood Operations:Operations:Definition of cells to include in processing is a zonal function.

Some uses: - Statistical analysis of zones (e.g., histograms)- distances, proximity and connectivity- buffering (point, line or area)- Viewshed Analysis (inter-visibility between points)

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Regional (Global) Regional (Global) Operations:Operations:

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Definition of cells to include in processing is potentially a function of regions in the raster layer.

Some uses: - clumping/parceling and reclassification - calculation of area, perimeter and shape- category-wide overlay (extracting, intersection)

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Regional (Global) Regional (Global) Operations:Operations:

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Some uses: - clumping/parceling and reclassification - calculation of area, perimeter and shape- category-wide overlay (extracting, intersection)

Air photo in the Rear of Leeds and Landsdownetownship. Northern portion of the photo indicates naturally occurring complex coniferous forest patch shapes compared to the surveyed and human modified deciduous forest plots in the south

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Prescriptive Cartographic Models Prescriptive Cartographic Models ––

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“By organizing the different primary operations for a particulardata analysis, a generalized approach to cartographic modelingmay be developed” (D. Tomlin, 1983).

• prescriptive cartographic models are solution oriented answering questions like “what should be done”;

• a cartographic model is a graphical representation of the data and procedures used in a logical sequence;

• serves as a specific project management tool and documentation tool

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Prescriptive Cartographic Models Prescriptive Cartographic Models ––Mapping a SolutionMapping a Solution

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Desirable Conditions = ”Timber” NOT (“Habitat” OR “StreamBuf”)

Simple constraint mapping cartographic model

End.