Raster Images in GIS

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Raster Images in GIS

• MapObjects User Group
• California Region
• Jeremy Bart
• jbart_at_esri.com

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What is a Raster Image?

• Represents geographic features by dividing the
  world into discrete units called Cells
• Grid made up of Rows and Columns
• Origin at upper left corner
• Cells contain values
• Each value stored in a band
• Used to represent thematic and spectral data, and
  pictures

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MapObjects 2.1

• Supported Image Formats
• BMP, GIF, JPEG
• ArcInfo GRID
• ERDAS IMAGINE
• ADRG, CADRG
• BIL, BIP, BSQ, RLC
• ASRP/USRP, CIB, CRP, NITF
• GeoTIFF, TIFF
• MrSID, Sun raster
• Image Catalogs

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MapObjects 2.1

• Improved output
• Export with different palettes
• Grayscale
• Web Safe (undithered)

• Export rotated transparent images
• Direct output to JPEG

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MapObjects 2.1

• Georeferenced Images
• Raster image stored in Rows and Columns
• Pixels start at upper left corner
• Image-to-world transformation
• Image coordinates to Map coordinates
• World File
• Dimensions of pixel in map units
• Rotation
• Location of upper left pixel in map units

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ArcGIS Raster

• ArcGIS core functionality
• Graphics
• Rendering
• Data conversion
• Transparency
• Selection
• On cells
• Georeferencing
• Stretch, Scale, and Rotate

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ArcGIS Raster

• ArcInfo GRIDS
• ArcSDE Raster and Raster catalogs
• Supported image formats
• BMP, GIF, JPEG, PNG
• ERDAS IMAGINE, LAN, GIS, Raw
• DTED Level 1 and 2
• ER Mapper
• ADRG, CADRG
• BIL, BIP, BSQ
• CIB, NITF
• GeoTIFF, TIFF
• MrSID
• Custom formats

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Georeferencing a Raster

• Using ArcMap
• Assign coordinate system
• Select transformation order
• Add control points to known positions in map
  coordinates (3 minimum)
• Update georeferencing to save transformation with
  the raster (.aux)

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Georeferencing Toolbar
Add Control Points
Show Link Table
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What is ArcObjects?

• Set of COM components used to develop ArcGIS
  applications
• Building blocks of ArcMap and ArcCatalog
• Object-oriented geographic data model
• Over 1500 classes in many OMDs
• Not a stand-alone product

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Raster Object Model

• Part of ArcObjects Object Model
• RDO used to
• Access raster data
• Access pixels
• Manage raster data
• Render and visualize raster data
• Convert raster data
• Work with any supported data format

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Simplified Raster Object Model
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Basic Raster Architecture

• RasterDataset abstraction of any raster format
• Is a container of RasterBands
• Is what we have
• Has static nature
• Raster vehicle to transport pixels in memory
• Is a container of RasterBands
• Is what we want
• Has dynamic nature
• RasterBand storage of pixels on disk or in
  memory
• Is a container of pixels
• Can be static or dynamic

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Accessing cells in a Raster

• The Raster object exposes a PixelBlock object.
• The PixelBlock is a container for a pixel or
  pixel array from a Raster.
• Used for query and to hook up custom analysis
  functions.

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Visualizing Raster data

• ArcObjects classes
• RasterLayer
• RasterRenderer
• Rendering rules
• Can create custom renderers

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Georeferencing a Raster

• Using ArcObjects
• IGeoReference on RasterLayer coclass
• CanGeoRef property is True
• PointsTransform method using tie points
  collection
• Register method to save transformation parameters
  and tie points to disk
• or
• Rectify method to create a new, transformed raster

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ArcGIS Spatial Analyst 8.1

• Combines ArcInfo GRID and ArcView 3.x Spatial
  Analyst
• Analysis on all raster formats
• Analysis on all vector formats
• More functions and options in UI
• Transparent data integration
• Full support of selections
• On-the-fly projections
• Calculator with Map Algebra syntax
• Better extensibility

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Spatial Analyst Toolbar
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Spatial Analyst Experience

• Select a function, select a dataset, fill in
  parameters, see the result
• Simple menu interface
• Immediate feedback
• Display and analysis integration

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Analysis

• Mathematical Operators and Functions
• Distance and Proximity Analysis
• Density Mapping
• Neighborhood and Block Statistics
• Zonal Overlay
• Interpolation and Contouring
• Surface Analysis
• Hydrologic Analysis
• Reclassification
• Geometric Transformation
• Morphological Analysis

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Spatial Analyst Object Model

• Functional grouping of commands exposed through
  COM interfaces
• Integrated Raster Analysis Environment
• Seamless data integration
• Deferred evaluation and Temporary Datasets
• GRID Map Algebra

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S.M.U.G.

• Our URL
• www.sacpublicworks.net/smug

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Using the RDO

• Easy to use COM Objects
• Format transparency
• A raster is a raster
• Read pixel data
• Output analysis results
• Add analysis results back to ArcMap