Key concepts about adding raster data to a map

When you add a raster dataset layer to ArcMap, you can choose to display a single band of data or a color composite from three bands of data.

You can also choose to add a raster dataset as a picture (map element) in the layout view. These rasters usually represent nongraphic images, such as a company logo or a picture of a house for a real estate map.

If you have data covering the same geographic area but in different coordinate systems, ArcMap uses the coordinate system of the first dataset added to the data frame and transforms any other data on the fly into this coordinate system. This applies to any feature class or raster data (including raster datasets, raster catalogs, and mosaic datasets).

For ArcMap to recognize your raster's coordinate system, it must be defined. If it is not already defined in the file format, you can modify it from the Properties dialog box or by using the Define Projection tool.

If your raster dataset does not have any georeferencing information associated with it (such as pixel size, coordinates, or a coordinate system), you can georeference it in ArcMap. See Georeferencing a raster dataset.

Raster catalogs are used to display multiple or adjacent raster datasets without merging or mosaicking them into one larger file. They appear on the Add Data dialog box in ArcMap within geodatabases as raster catalog objects (or as ordinary tables).

When displayed in ArcMap, the raster datasets in the raster catalog are drawn in order from the first to last record in the catalog's table. If there are more than nine rasters in the raster catalog, the layer will draw as a wireframe, representing the boundaries of each raster. You can change this default setting on the Layer Properties dialog box under the Display tab.

A raster catalog can contain multiple raster types, formats, resolutions, and file sizes. To create a raster catalog in a geodatabase, there are two main steps: Create the raster catalog in the geodatabase and load the raster datasets into the raster catalog. These operations can be performed with tools in both ArcCatalog and ArcToolbox.

You can also create a legacy image catalog using a table file format. Any table format can be used to define an image catalog, including text files (for example, .dbf). For these image catalogs, the table requires five columns: IMAGE, XMIN, YMIN, XMAX, and YMAX.

Mosaic datasets are a hybrid of a raster catalog and raster dataset—they represents an on-the-fly mosaic view of a raster catalog. Like raster catalogs, mosaic datasets can contain multiple raster types, formats, resolutions, and file sizes; however, when you view them in ArcMap, you can view the footprints for each raster and the mosaicked image. The method in which the images are mosaicked and displayed is controlled through the mosaic properties, such as the mosaic method.

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