best practices: working with raster data in arcgis agenda • varieties of raster data •...

Best Practices: Working with Raster Data in Best Practices: Working with Raster Data in ArcGISArcGIS DesktopDesktop

Amadea AzerkiAmadea AzerkiCA/HI/NV RUG 2008CA/HI/NV RUG 2008

Sacramento, CASacramento, CA

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AgendaAgenda

Varieties of Raster DataVarieties of Raster Data Raster Data StorageRaster Data Storage

Raster datasets, catalogs, data type RasterRaster datasets, catalogs, data type Raster

Raster Data PropertiesRaster Data Properties Pyramids,Pyramids, NoDataNoData settings, auxiliary filessettings, auxiliary files

Displaying Raster Data in Displaying Raster Data in ArcMapArcMap Manipulating Raster DataManipulating Raster Data Printing Tips and TricksPrinting Tips and Tricks Q & AQ & A

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Varieties of Raster DataVarieties of Raster Data

Elevation or Elevation or HillshadeHillshade

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Varieties of Raster DataVarieties of Raster Data

Aerial ImageryAerial Imagery

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OrthorectifiedOrthorectified ImageryImagery

No correctionNo correction

OrthorectifiedOrthorectified

Varieties of Raster DataVarieties of Raster Data

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Satellite ImagerySatellite Imagery

Varieties of Raster DataVarieties of Raster Data

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Scanned MapsScanned Maps

Varieties of Raster DataVarieties of Raster Data

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Inserted Pictures or GraphicsInserted Pictures or Graphics

Varieties of Raster DataVarieties of Raster Data

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Attributes of type Raster Attributes of type Raster in a feature classin a feature class

Varieties of Raster DataVarieties of Raster Data

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Specifying Raster Data TypesSpecifying Raster Data Types

Consider slow response in Consider slow response in ArcMapArcMap oror ArcCatalogArcCatalog

Numerous Raster FormatsNumerous Raster Formats DefaultDefault CustomCustom

Search ModeSearch Mode All files takes timeAll files takes time Ability to add new file typesAbility to add new file types

Minimize connectionsMinimize connections Delete connection to C:Delete connection to C: Specify project foldersSpecify project folders

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Raster Data Storage in Raster Data Storage in ArcGISArcGIS

Raster datasetRaster dataset Any valid raster format that organizes Any valid raster format that organizes

data into bandsdata into bands Includes mosaicsIncludes mosaics

Raster catalogRaster catalog A collection of raster datasets stored A collection of raster datasets stored

in a table, as rowsin a table, as rows

Assigning raster as an attributeAssigning raster as an attribute An attribute for a feature designated An attribute for a feature designated

as data type as data type rasterraster

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Raster PropertiesRaster Properties

Data sourceData source Type of file and locationType of file and location

Raster informationRaster information Pixel type, cell size, Pixel type, cell size,

format, pyramid format, pyramid information, etc.information, etc.

ExtentExtent Top, bottom, left and right Top, bottom, left and right

extentsextents Spatial referenceSpatial reference

Coordinate system Coordinate system informationinformation

StatisticsStatistics Min, max, mean, and Min, max, mean, and

standard deviation (per standard deviation (per band)band)

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Raster Properties ContinuedRaster Properties Continued

Storage PropertiesStorage Properties PyramidsPyramids NoDataNoData CompressionCompression

Display PropertiesDisplay Properties Auxiliary filesAuxiliary files Color mapsColor maps StatisticsStatistics

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Raster Properties Raster Properties -- PyramidsPyramids

Reduced resolution views of the original rasterReduced resolution views of the original raster Pixel size doubles at each levelPixel size doubles at each level Stored as an .RRD fileStored as an .RRD file

Improves display performanceImproves display performance Zoom in/out to different scalesZoom in/out to different scales

Appropriate level of resolution is usedAppropriate level of resolution is used ResampledResampled data is displayeddata is displayed

Need to create only onceNeed to create only once Adds about 33% more storageAdds about 33% more storage

to the uncompressed sizeto the uncompressed size

Pyramids are not used during Pyramids are not used during analysisanalysis

2x2 pixelblock

2x2 pixelblock

1 meter

1st (2 m)

2nd (4 m)

3rd (8 m)

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Building PyramidsBuilding Pyramids

To Build or Not to Build?To Build or Not to Build?

Building PyramidsBuilding Pyramids Long draw time on initial viewingLong draw time on initial viewing Saves time afterwardsSaves time afterwards Requires extra storage spaceRequires extra storage space May need to delete pyramids if May need to delete pyramids if

moving datamoving data

Not Building PyramidsNot Building Pyramids Slow to draw every timeSlow to draw every time Minimizes storage spaceMinimizes storage space Preferable if rarely viewing dataPreferable if rarely viewing data

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Raster Properties Raster Properties -- NoDataNoData

NoDataNoData = Cells or pixels that have unknown values= Cells or pixels that have unknown values NoData and "0" are not the same, "0" is a valid valueNoData and "0" are not the same, "0" is a valid value Often appears black by default, can change to a color or make Often appears black by default, can change to a color or make

transparenttransparent Useful for rotated Useful for rotated rastersrasters with unwanted backgroundwith unwanted background Does not participate in statistics calculationsDoes not participate in statistics calculations

StorageStorage As a value for fileAs a value for file--basedbasedrastersrasters As a bit mask for As a bit mask for ArcSDEArcSDEand fileand file--GDBGDB rastersrasters Saves disk spaceSaves disk space

Pixels & NoData

NotStored

Pixels Only

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Raster Properties Raster Properties -- CompressionCompression

Reduces storage sizeReduces storage size

Improves overall performanceImproves overall performance

Compression type Compression type Determined by data, storage requirements and useDetermined by data, storage requirements and use LossyLossy vs. Losslessvs. Lossless

1.5 GB1.5 GB 150 MB150 MBCompressionCompression

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Raster Properties Raster Properties -- LossyLossy vs. Lossless Compression vs. Lossless Compression

ChooseChoose LossyLossy Compression:Compression: Raster data will only serve as backgroundRaster data will only serve as background No analysis needed No analysis needed For faster data loading and retrieval For faster data loading and retrieval Less storage space is neededLess storage space is needed

Choose Lossless Compression:Choose Lossless Compression: If using raster data to derive new dataIf using raster data to derive new data Perform visual or spatial analysis Perform visual or spatial analysis DonDont plan to retain the original data t plan to retain the original data Input raster data are already Input raster data are already lossylossy compressed compressed

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Raster Properties Raster Properties -- Auxiliary FilesAuxiliary Files

Auxiliary file is tagged as either AUX or AUX.XMLAuxiliary file is tagged as either AUX or AUX.XML

Created automatically when raster data is viewed in Created automatically when raster data is viewed in ArcGISArcGIS

Stores any information that cannot be stored in the raster file Stores any information that cannot be stored in the raster file itself (differs by raster format)itself (differs by raster format)

Color mapColor map Pointer to the pyramid filePointer to the pyramid file Statistics and histogramStatistics and histogram Coordinate systemCoordinate system TransformationTransformation Projection informationProjection information

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Raster Properties Raster Properties -- ColormapsColormaps

Applying a Applying a colormapcolormap Set of values associated with specific colors (RGB)Set of values associated with specific colors (RGB) Stored as part of a raster datasetStored as part of a raster dataset Defines how to render each pixelDefines how to render each pixel Used to consistently display data with the same colorsUsed to consistently display data with the same colors Capable of handling up to 8Capable of handling up to 8--bit data (256 colors)bit data (256 colors)

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Raster Properties Raster Properties -- StatisticsStatistics

To perform specific tasksTo perform specific tasks Applying contrastApplying contrast Stretching dataStretching data Reclassifying dataReclassifying data

Created using the Calculate Statistics toolCreated using the Calculate Statistics tool

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Five Types of Five Types of RenderersRenderers StretchedStretched Unique Values Unique Values ColormapColormap RGB CompositeRGB Composite ClassifiedClassified

Displaying Raster DataDisplaying Raster Data

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Raster RenderingRaster Rendering

StretchedStretched Stretches values along a color rampStretches values along a color ramp Default: Raster has more than 25 unique valuesDefault: Raster has more than 25 unique values

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Raster RenderingRaster Rendering

Unique ValuesUnique Values Uses random colors for individual valuesUses random colors for individual values Default: Raster has fewer than 25 unique valuesDefault: Raster has fewer than 25 unique values

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Ra