U.S. Department of the InteriorU.S. Geological Survey

Building Base Maps

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Managing large image collections

• Large images can easily exceed the 2-GB limit on file size

• ESRI offers two major ways to manage spatially tiled images– Image Catalogs– ArcSDE Rasters (has 5 ways to handle,

but beyond scope of this class)

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Raster (a.k.a Image) Catalogs

• Group of raster files covering a similar theme and sharing coordinate system

• Often same format and symbology

• Examples:–Map series (DRGs)– Orthophotos (DOQs)

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Raster Catalogs

• Display multiple rasters without having to merge them into larger rasters

• Supported very well in ArcView 3 • Supported in ArcPlot, but can’t do a

transparent NODATA• Also supported in ArcMap, but you need a

script to do transparent NODATA

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Raster Catalogs

• Format: any table with columns:IMAGE, XMIN, YMIN, XMAX, YMAX

• IMAGE is a pathname to the raster• Symbology from first raster in

catalog• ArcObjects Online sample code

exists to help in symbolizing catalogs

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Working with Image Catalogs

• Prerequisites:– Images in supported formats– Georeferenced, spatial reference

specified in ArcCatalog– All images must use the same colormap– If overlapping, need a special value for

overlaps or NODATA areas

Image Catalog Procedures:DRG Example

• Get DRGs. Best source: NRCS state offices on CD

• Decide on projection, datum• Clip_project_DRG.aml

– Project if necessary– Trim collars

• Assign spatial reference: BatchRasterSpatialRef.bas

• Use a system variable for base of paths in image catalog for portablility

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Create Image Catalogs

• Arc CREATECATALOG command• Arc ADDIMAGE command• Drgcatalog.aml does both, adds all images

in a folder to the catalog• Folder2ImageCatalog.bas works in

ArcCatalog, can do .SID files• Other AMLs:– copyimagecat.aml (copies images)– trimimagecat.aml (deletes images from disk)

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Raster Catalog Pitfalls

• Make sure all files and folders are NOT read-only

• Do NOT load into ArcMap until you are sure all paths are correct and all images have spatial references

• If you load it with a bad spatial reference you will never be able to load it correctly

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Changing Symbology for an Raster Catalog

• No Symbology tab

• There’s no way to store a transparent color in a TIFF colormap

• Must use a script to get a ‘renderer’ from one image, apply it to all

• ChangeCatalogSymbology.bas

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Other base maps

• NLCD

• Shaded relief at both 90- and 30-meter resolutions

• Precip, other layers used

• Make these TIFFs, they work better in ArcIMS