geographic information systems (gis) in planning and ... · prescriptive cartographic models –...
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Geographic Information Systems (GIS)in Planning and Resource Management
ENVS 6189 3.0 - lecture 7
John Sorrell
York University. [email protected]
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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.
GIS in Environmental Studies
..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:
GIS in Environmental Studies
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:
GIS in Environmental Studies
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.
GIS in Environmental Studies
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Local Operations:Local Operations:ReclassReclass -- OverlayOverlay
GIS in Environmental Studies
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)
GIS in Environmental Studies
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)
GIS in Environmental Studies
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 :
GIS in Environmental Studies
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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GIS in Environmental Studies
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:
GIS in Environmental Studies
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:
GIS in Environmental Studies
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
GIS in Environmental Studies
Desirable Conditions = ”Timber” NOT (“Habitat” OR “StreamBuf”)
Simple constraint mapping cartographic model
End.