About analyzing raster data
There are many ways that you can work with raster data when doing an analysis—you may want to visually analyze the raster data, use it as a background (basemap) to visually analyze other data, or use it in an analysis operation.
If you're using the raster data in a visual analysis, you may be examining the results of a watershed study or looking for features in a shaded relief created from a digital elevation model (DEM). If you're using the raster data to help analyze other data, you may be examining and updating vector data, such as roads, by using up-to-date raster data as a basemap to determine the location of any missing roads. For any of these types of analyses, you are most likely concerned with the visual appearance of the raster. You should consider the types of renderers used to display the rasters (such as the Stretched or RGB Composite renderers) and may want to alter these, apply different types of stretches to the histogram to enhance specific information in the raster dataset, or even remove some of the values of the raster from the display.
For information on displaying rasters using the different types of renderers, see Renderers used to display raster data. For information on other aspects of a raster's appearance and behavior, such as faster rendering, performance tuning, enhancing the contrast, or changing the appearance of background values, see Improving the display of raster data. There are also tools to balance the appearance of multiple images to make them look like a single seamless image. For more information, see Color correction of raster data or Color correcting a mosaic dataset.
There are additional tools in ArcMap to help you in your analysis of raster data, such as the Pixel Inspector tool , which is used to view an area of pixel values in your raster dataset, or the Swipe Layer tool , which is used to interactively reveal layers beneath the layer being swiped. To learn about these tools and others, see the following:
You can also use the Identify tool to get pixel value information for a single pixel, or use the Get Cell Value tool when you're working in a geoprocessing model.
The Image Analysis window provides both processing and display capabilities for raster data. You can easily display a DEM as a shaded relief and modify the color ramp. There is also a tool to perform a difference so you can see if there have been any changes between two datasets, and you can easily merge multiple rasters into one.
One special characteristic the Image Analysis window provides is the capability of adding functions to the raster layers. You can modify these functions and perform more advanced analysis on your raster data. These functions are applied as you access the data and are saved within the layer files.
There are many ways to use raster data in analysis operations. When performing these operations, your main concern will probably be with the data represented by the values of the cells; therefore, you will be performing operations that manipulate these values. There are many tools in ArcGIS Desktop that allow you to work with raster data for data management, conversion, and transforming; however, to utilize raster data within an analysis operation, you will need one of the extensions.
There are two extensions to ArcGIS that enhance the analysis capabilities of raster data. These are
- ArcGIS Spatial Analyst—This extension provides a comprehensive set of advanced spatial modeling and analysis tools that allow you to perform integrated raster and vector analysis.
- ArcGIS 3D Analyst—This extension allows you to effectively visualize, analyze, and generate surface data and provides the tools for three-dimensional modeling and analysis.
When using the geoprocessing tools provided by ArcGIS or either of these extensions, you can automate your workflows by building models to perform your analysis. Building models allows you to chain the tools together. To learn more about building models, see What is ModelBuilder.