Symbols can be rotated based on a numeric value, useful for showing the direction a camera is pointing, a car is moving, the wind is blowing, and more. The data must have a field containing values that will be used for rotation, typically a compass direction with clockwise values of zero at north, 90 east, 180 south, and so on.
But compass azimuths aren’t required for rotating symbols, and you can use any value that makes sense for your needs. You can set the rotation angles to be measured clockwise, or counter-clockwise, depending on how values are stored.
Note that when rotating clockwise that angles are measured clockwise from the 12 o’clock position, and when rotating counterclockwise the angles are measured counterclockwise from the 3 o’clock position.
Symbol rotation exercise
Download the sample CSV used in this example and follow along. The CSV file includes web cam locations (dummy locations, not actual locations) as well as the direction the camera is pointing expressed as clockwise compass azimuths.
Step 1 – Inspect the data.
Open the file using Excel, Notepad, or some other text editor to view the contents. Note that the file contains the lat/long location, as well as Direction, which will be used to rotate the symbol.
Step 2 – Add the data to your map.
Add the CSV data to a new map. You can drag and drop the file onto your map, or choose Add, then Add Layer from File.
Step 3 – Change the style of the locations.
When you add the CSV file in Step 2 above, Change Style automatically opens. Choose Show location only, then click Options.
Step 4 – Click Symbols to change the point symbols.
Step 5 – Choose an arrow symbol.
Choose an arrow symbol from the Arrows category. Since the rotation is stored as compass directions with zero pointing north (up), choose an arrow that points up.
Change the symbol size as desired, then click OK.
Step 6 – Rotate the symbol.
a. Check the Rotate symbols (degrees) box.
b. From the dropdown, choose the field containing the values used for rotation. In this case, the field is Direction.
c. The values are already stored in the expected clockwise format described above, so Geographic (the default) is the correct rotation option.
Save your style changes when finished.
Step 7 – View the map.
The map now displays the camera locations with the arrow rotated to show the direction of each camera.
Rotation can be applied to any feature layer in your map. Below is an example showing captured locations for inbound and outbound planes traveling from San Francisco to Los Angeles via San Diego. The layer source is a shapefile, and custom symbols were created to symbolize the inbound and outbound traffic.
This example uses a technique of stacking symbols to create a gauge and dial, and using symbol rotation to rotate the dial.
For more information see Creating dials and gauges using stacked symbols and rotation.
This next example uses Arcade to rotate a dial to show reservoir capacity. Arcade is an expression language built-in to ArcGIS Online.
For more information see Change style.
This post was originally published on January 6, 2014, and has been updated.