Use comparison tools

Use the comparison tools to conduct visual analysis and find differences in imagery to complete an image-based task. The comparison tools contain features to highlight areas of interest through layer comparison and change detection.

Use the Swipe tool

The Swipe tool allows you to interactively compare two layers vertically or horizontally in the Map Panel. This allows you to see what is underneath the layer you are focused on while analyzing imagery.

The Primary and Comparison layer drop-down menus will always contain the image layers but will also display images that you selected from the metadata table. Only two layers can be compared at a time. The web map is not available as a Comparison layer and is only available as an option for a Primary layer.

To use the Swipe tool, complete the following steps:

1. Click the Tools menu in the canvas.
2. In the Comparison Tools list, click Swipe.
3. Select a Primary layer.
4. Select a Comparison layer.

   Note:

   The basemap is not available as a Comparison layer.

5. Choose a swipe bar direction.

   Note:

   The default swipe direction is vertical.

6. Click Apply.

   The Primary and Comparison layer names will be added as a label in the Map Panel to provide context as to which image is displaying.

7. Use the Swipe tool controls in the Map Panel Header to change the swipe direction or to reset the tool and start again.

Note:

If the Map Panel is not visible, the Swipe tool is unavailable.

Use the Flicker tool

The Flicker tool is used to visually compare images. The Flicker tool allows you to display multiple layers underneath other layers by quickly turning it on and off automatically based on a defined rate. This can be useful for temporal change detection, data quality comparison, and other analysis you want to see between layers.

The Flicker tool is accessed from the Tools menu under Comparison Tools. The Map Panel must be visible to use the Flicker tool. The Web Map and Image Layer options are always available to you. The images you select from the metadata table are the images that will appear in the drop-down menu to apply to the Flicker tool.

The default and minimum flicker interval rate is half of a second (500 ms), while the maximum rate is five seconds (5000 ms). To use the Flicker tool:

1. Click the Tools menu in the canvas.
2. In the Comparison Tools list, click Flicker.
3. Select at least two layers to be applied to the Flicker tool.
4. You can use the Move Up or Move Down buttons to set the order of how the images will be displayed when they are played.
5. Click Apply.
6. Choose a rate.
7. Click Play.

   As the tool plays, the active layer name will be added as a label in the map panel to provide context as to which image is displaying.

   The imagery layers are locked once Play is clicked.

8. Use the Flicker tool controls in the map header panel to play or pause the tool, jump to the start or end of the images, or to reset the tool if you want to use another tool at the same time as the Flicker tool.
9. Click Pause to halt the Flicker tool or to choose new images to compare.
10. Click Reset to return to the default settings of the tool.

Use the Detect Change tool

The Detect Change tool conducts automated pixel-based comparisons between two images selected in the image metadata table. This tool detects image change using multiple raster functions.

The tool must be run against two different raster IDs from a single image service that is query and search enabled. Once these images are selected, you can define the area of interest that the tool will run against. Results are returned as in-memory graphics that you can use for immediate visual comparison or in Excalibur project reports.

To use the Detect Change tool, complete the following steps:

1. Click the Tools menu in the canvas.
2. In the Comparison Tools list, click Detect Change.
3. Choose an image for Input Image 1.

   If no images are selected in the image metadata table, a message will show in the view.

4. Choose an image for Input Image 2.

   You cannot choose the same image as Input Image 1.

5. Click Sketch Area of Interest.
6. Draw and define an area of interest. Click Clear and Reset Drawing to close the tool.

   If the area of interest is drawn outside of the selected image extent, an error notification will display.

7. Optionally, adjust your transparency and threshold using the sliders.

   You can also change the color of your detection when it appears.

8. Click Run.

   Results are dynamically returned as graphics on the image.

9. Click Reset to clear the results, selected images, and the drawn area of interest.

Note:

The tool is unavailable if the active image service is non-query enabled or not an ArcGIS imagery layer. If there is only one image in the image metadata table, the tool will also be unavailable as a minimum of two selected images is required to run the tool.