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Raster Images in GIS

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Used for query and to hook up custom analysis functions. 15. Visualizing Raster data ... Can create custom renderers. 16. Georeferencing a Raster. Using ArcObjects: ... – PowerPoint PPT presentation

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Title: Raster Images in GIS


1
Raster Images in GIS
  • MapObjects User Group
  • California Region
  • Jeremy Bart
  • jbart_at_esri.com

2
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

3
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

4
MapObjects 2.1
  • Improved output
  • Export with different palettes
  • Grayscale
  • Web Safe (undithered)
  • Export rotated transparent images
  • Direct output to JPEG

5
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

6
ArcGIS Raster
  • ArcGIS core functionality
  • Graphics
  • Rendering
  • Data conversion
  • Transparency
  • Selection
  • On cells
  • Georeferencing
  • Stretch, Scale, and Rotate

7
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

8
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)

9
Georeferencing Toolbar
Add Control Points
Show Link Table
10
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

11
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

12
Simplified Raster Object Model
13
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

14
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.

15
Visualizing Raster data
  • ArcObjects classes
  • RasterLayer
  • RasterRenderer
  • Rendering rules
  • Can create custom renderers

16
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

17
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

18
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19
Spatial Analyst Toolbar
20
Spatial Analyst Experience
  • Select a function, select a dataset, fill in
    parameters, see the result
  • Simple menu interface
  • Immediate feedback
  • Display and analysis integration

21
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

22
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

23
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24
S.M.U.G.
  • Our URL
  • www.sacpublicworks.net/smug

25
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
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