For this example, I'll be using a basic outline of London's Hyde Park as an overlay. This is a PNG file, however many file types are supported (full list of supported image types here) but the basic rule of thumb is to keep your file sizes small.
This overlay is transparent to better show how it's sitting on the map for this demonstration.
I've also created a new event and added markers to the South West and North East corners of the event area on the map. These markers not only act as the corners of the grid, but also as the corners of the overlay image we're about to place on top.
If you are unfamiliar with creating an event, please read the Create Event help article.
To upload an overlay, first select 'Choose file' from the overlay section in the event editor.
In the finder window that appears, navigate to the overlay file on your computer and click 'Open'.
With your file selected, click 'Update Event' to upload it.
Once your overlay has uploaded, you should now have the image displayed over the map section.
As you can see, this overlay has been placed in not quite the right size and position, so now we need to do a little fine-tuning to get the overlay sitting correctly on the map.
To reposition/resize the map, we'll need to move the corner markers. To do this, simply drag and drop the marker to your desired position. You will need to refresh the page every time you move the marker to update the overlay image.
This process will take a little patience and finesse to get right, so don't feel bad if you don't get it right first time. Moving in small increments is advisable.
This corner is now in the correct position - time to check on the other corner!
Again, moving the marker in small increments, refreshing after every move to see where the overlay sits until it fits.
Use the landmarks marked on your overlay to help position the map correctly (note the edge of the lake lining up with the satellite photo).
Once both corner markers are in the correct position, your overlay should now be correctly situated on the main dispatch map. You are now ready to use this overlay to better inform your dispatch operators and terminal users in the field about the lay of the land.
Please note: This overlay will only be displayed on the map of the event you have attached it to. It will not display on main dispatch and to use it in other events will require going through this process again for each event.
If you have completed this process and are unable to see the overlay map when exiting edit mode, it is likely because you are not viewing the event you assigned it to.
See also: For more information on creating and editing events, see Creating Events.