CFR 250/590 Introduction to GIS, Autumn 1999 Raster Analysis I © Phil Hurvitz, 1999-2000raster1.ppt...

© Phil Hurvitz, 1999-2000

CFR 250/590 Introduction to GIS, Autumn 1999

raster1.ppt 1

Raster Analysis I

Overview

• Grid themes

• Setting grid theme and analysis properties

• Projections and grid themes

• Grid function types

• Performing grid analysis

• Map Algebra



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Raster Analysis I

Grid themes

• Overview

• Grid theme types

• Grid theme properties

• Adding grid themes to views

• Displaying grid themes

• Examining cell values in grid themes

• Managing grid theme files



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Raster Analysis I

Grid themes: Overview

• Grid themes are ArcView’s implementation of the basic raster data model.

rectangular tessellation of square cells



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Raster Analysis I


• Grid themes are ArcView’s implementation of the basic raster data model.

•each cell has a numeric value

cell values are

displayed in the

legend



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Raster Analysis I


• Grid themes are good for representation of phenomena that vary gradually over space

such as elevation, wind speed and direction, or slope



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Raster Analysis I

Grid themes: Grid types

floating-point

integer

only integer grids have theme tables



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Raster Analysis I

Grid themes: The spatial analyst

•All grid theme functionality occurs through the spatial analyst extension.



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Raster Analysis I

Grid themes: Grid theme properties

name disk location

cell size

rows

&

columns

type

status

bounding coordinates



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Raster Analysis I

Grid themes: Adding grid themes to views

updated theme list

new Data Source Type choice



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Raster Analysis I

Grid themes: Displaying grid themes

usually numerically classified



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Raster Analysis I

Grid themes: Examining cell values in grid themes

histogram shades match theme legends



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Raster Analysis I


histograms can be createdfor polygonal zones



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Raster Analysis I


integer grid



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Raster Analysis I


integer

grid



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Raster Analysis I

Grid themes: Managing grid theme data files (and shapefiles)

new menu choice



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Raster Analysis I

Grid themes: Managing grid theme data files (and shapefiles)

delete

rename

copy

sourcetype

datasourcename



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Raster Analysis I

Setting grid theme and analysis properties

• Spatial extent

• Cell size

• Masking

Analysis properties determine grid theme properties for all output grid themes



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Raster Analysis I

Setting grid theme and analysis properties: Spatial extent



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Raster Analysis I

Setting grid theme and analysis properties: Cell size



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Raster Analysis I

Setting grid theme and analysis properties: Masking



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Raster Analysis I

Setting grid theme and analysis properties: Masking



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Raster Analysis I

Projections and grid themes

ArcView cannot project grid themes on the fly as it projects feature themes.

• Do not view unprojected grid themes with projected vector themes.

• View projected grid themes with unprojected vector themes by setting view projection properties.

• If you need to project a grid theme to match projected vector themes, use ARC/INFO.



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Raster Analysis I

Grid function types

• Global functions

• Zonal functions

• Focal functions



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Raster Analysis I

Grid function types: Global functions

Global functions apply one calculation to all input grid cells.

global sine



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Raster Analysis I

Grid function types: Zonal functions

Zonal functions apply one calculation to all input grid cells within each zone.

zonal sum



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Raster Analysis I

Grid function types: Focal functions

Focal functions apply one calculation to all input grid cells within a “focus.”

focal mean



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Raster Analysis I

Performing grid analysis: Map algebra (or “How it works”)

• multiple grid themes share the same X, Y coordinate space

• cell values are calculated across multiple grid themes



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Raster Analysis I

Performing grid analysis: Map algebra

map algebra calculations are performed with GUI tools

grid themes(layers)

operators

expression box

operator classes



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Raster Analysis I

Performing grid analysis: Map algebra (or “How it works”)

grid themes may be used in algebraic functions

output_data_set = function (input_data_set(s) {,arguments})slp_grid = slope (dem, percentrise)

grid themes may be used in algebraic expressions

output_data_set = input_grid1 operator input_grid2 . . .

slp_dem = slp_grid * dem

CFR 250/590 Introduction to GIS, Autumn 1999 Raster Analysis I © Phil Hurvitz, 1999-2000raster1.ppt...

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Transcript of CFR 250/590 Introduction to GIS, Autumn 1999 Raster Analysis I © Phil Hurvitz, 1999-2000raster1.ppt...