Under Raster Layer, on the Appearance tab, you will find all of the essential raster functionality to adjust the display and appearance of your imagery.
Use the In Beyond and Out Beyond menus to limit the visibility of a raster to be between specific scales. Choose from one of the preset options in the drop-down menu or enter a different scale in the text box. Use the Clear Limits button to remove the visibility settings.
The Effects options enable you to compare two overlapping rasters. Use the Transparency slider to reduce the opacity of the selected raster. Doing so will make the underlying raster visible. The selected raster needs to be the uppermost layer that is enabled in the Contents pane in order for you to visualize the transparency. You can also use the Swipe tool to peel back the raster on top, revealing the raster that's under it. To deactivate Swipe, on the Map tab, click the Explore button.
The Rendering options enable you to control the display of rasters and imagery by adjusting the Symbology, Stretch Type, Dynamic Range Adjustment (DRA), Resampling Type, Band Combination, and Masking.
The Symbology button is the principle interface for managing the display controls. The lower portion of the icon is a drop-down menu that offers you a selection of renderers specific to the type of data you are working with. If you hover over the icon, the part of the button that is active will turn blue. Clicking on the icon will open up the Symbology pane, which gives you access to all of the parameters related to setting symbology, including the Stretch Type, Dynamic Range Adjustment (DRA), Resampling Type, and Band Combination, including quick access directly from the ribbon.
The Symbology options are as follows. For more information, see change the symbology of your imagery.
- Stretch displays values along a color ramp.
- RGB Composite displays the bands comprising the dataset as red, green, and blue.
- Classify assigns a color for each class or group of values.
- Unique Values assigns a color for each value.
- Colormap applies the color map associated with the dataset.
- Discrete applies a new color for each unique value until you reach the Number of colors specified; then the unique values start at the beginning of the color scheme until it reaches the Number of colors specified again. This rendering process continues until all the unique values have been displayed. This is helpful for rasters with a lot of unique values, where you do not need a legend.
You can control how the range of values is displayed with the drop-down list on the Stretch button. You can also control the range for each band you have displayed in an RGB composite.
The Stretch options are as follows:
- None displays the values on a scale from the potential minimum and maximum values. For example, if you have an 8-bit dataset, the values would be stretched from 0 to 255, regardless of the actual distribution of pixel values. None is a good choice if you will be examining multiple rasters and want to standardize the display.
- Minimum Maximum displays the values on a scale from the actual minimum and maximum values. For example, if you have an 8-bit dataset, but the values range from 20 to 225, the display is stretched from 20 to 255. This increases the ability to see differences in values throughout the dataset.
- Percent Clip cuts off a percentage of the highest and lowest values. This will reduce the effects of outliers and other noise in the datasets.
- Standard Deviation displays the values between a specified number of standard deviations.
- Esri stretch uses a modified Sigmoid stretch that uses an S curve to find the mean, which helps to prevent pixel values to be stretched to the extreme. This method is used to provide a good overall stretch to imagery.
Dynamic Range Adjustment, (DRA), is a feature that automatically adjusts your contrast stretch as you navigate around your image based on only the pixel values in your current display. You can turn this on or off by toggling the DRA button.
Alter the Resampling Type with the choices in the drop-down list. Nearest Neighbor retains the original pixel values, whereas the other resampling techniques produce a smoother image by interpolating values.
The Resampling Type options are as follows:
- Nearest Neighbor assigns the value from the closest pixel. This is appropriate for spectral analysis and classification because it preserves the original radiometry. It is also applied to qualitative data, such as land cover. The tradeoff with Nearest Neighbor is that you may see artifacts over linear features where the realignment of pixels is obvious.
- Bilinear interpolates the value from the neighboring 4 pixels. This is appropriate for continuous datasets, such as elevation.
- Cubic interpolates the value from the neighboring 16 pixels. This is appropriate for continuous datasets used for visualization purposes only. It produces a very smooth output, but it changes the values of the pixels more than Bilinear.
- Majority assigns the most popular value from the surrounding 4 pixels. This is appropriate for resampling categorical or integer data, such as land use, soil, or forest type. Majority resampling acts as a type of low-pass filter for discrete data, generalizing the data and filtering out anomalous data values.
Within the Band Combinations, there are defaults for natural color and a false color infrared, which will highlight vegetation on most sensors.
If you have a raster product or an image service selected in the Contents pane, you will see all of the band combinations associated with that data in the drop-down menu. Other popular band combinations are available depending on sensor type and bands. Below is an example from Landsat 8. You also have the option to create custom band combinations.
To do this, select Custom and load the bands you want into each color. When you click Add, you will be able to select it from the drop-down menu.
The Masking button allows you to choose a feature class in the Contents pane to mask out the selected raster. This is helpful if you already have a feature class of the area that needs to be masked out.
Adjust the display of a raster dataset using the sliders for Contrast, Brightness, and Gamma settings. Move the sliders accordingly or type in the desired values. To reset the sliders, click their respective icons.
When working with high-resolution imagery, shadows on tall buildings can become disorienting, and it can be easier to analyze imagery if buildings are facing upward. When your imagery has the necessary metadata, ArcGIS Pro will use that information to rotate the imagery so buildings are pointed toward the top of the image, using Top Up. To revert, you can use the North Up button.