ArcGIS is optimized to work with imagery and raster data. You can work with imagery from a satellite or aerial sensor or a raster dataset representing gravitational modeling, or a DEM. You can adjust the appearance of imagery to enhance specific features or merge an image with a hillshade. You can use it as a background (base image) to enhance the assessment or presentation of other data. You can also perform advanced analysis operations, such as finding areas of change or performing an image classification.
The Catalog window makes it easy to identify and view imagery and raster data by providing unique icons.
ArcGIS 10.1 makes working with satellite imagery easy with the new raster product. Raster products are actually raster datasets with some known associated metadata. They are standard products provided from several imagery vendors, such as satellite image products like Landsat or QuickBird. The application combines the bands to create one of several products, which makes it easier for you to add that data to your display. For example, Landsat 7 data appears with this raster product icon and, when expanded, allows you to choose a particular band combination to add to your display.
Adding imagery and raster data to ArcMap is straightforward. Navigate to the data in the Catalog window, then drag and drop it onto the display view in ArcMap. Depending on the properties of the data, ArcMap will render it accordingly.
Once added, the raster datasets appear in the table of contents, and if your raster dataset is within the extents of your display view, you will see the image. Optimized display parameters, including renderer type, stretching type, gamma, and contrast, are applied based on the properties of the data; therefore, if it's a single-band dataset, the grayscale stretch is applied. If that single band has a color map, the Colormap renderer is used. If it's a multiband image, the default RGB band combination is applied. If the input has the required wavelength information, a natural color band combination will be displayed. If it's a raster product, the bands are named appropriately. If it's a mosaic dataset, you can view the multiple layers that compose the datasets. And if it's a raster catalog with more than nine images in the display, it is displayed as polygons (a wireframe).
There are many tools on the Image Analysis window to help you improve the appearance of the image by altering how the histogram is stretched. The sliders adjust the contrast , brightness , and gamma of the image. The Interactive Histogram Stretch button is useful to help you understand the distribution of pixel values and adjust how they are stretched.
ArcGIS provides tools 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 access to 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 capability the Image Analysis window provides is adding functions to the raster layers. You can modify these functions and perform more advanced analysis on your raster data. Many of the buttons in the Processing section of the window insert functions into the layer. There is also an Add Function button to give you access to the function chain so you can pick the processing function you want applied and chain them together to create more complex analyses. These functions are applied as you access the data and are saved within the layer files.
The Image Analysis window also contains a set of mensuration tools, including tools to measure point, distance, angle, height, perimeter, and area from an image (raster dataset or mosaic dataset) with sensor information (or geodata transformation).
Mensuration is defined as applying geometric rules to find the length of lines, areas of surface, or volumes using the information obtained from lines and angles. It can also include measuring the height and absolution location of a feature.
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 for 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 ArcGIS extensions that enhance the analysis capabilities of raster data. These are
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.