Most premium maps sold via MyTrails are priced according to how much of the map you wish to store on your device. Within that limit, you can download the parts of the map you wish, and when you no longer need a given area, you can delete it and download a different area.
Because MyTrails allows you to use the map on different devices, just deleting the map on one device is not enough, the map needs to be unregistered on the server.
When you try to delete a an offline map you have created from a premium map, MyTrails asks whether you want to just delete the map locally (presumably it can still be used on another device) or also unregister it.
You only get the download credits back if you unregister the map. Even then, you may not get back the exact amount of credits corresponding to the area of the offline map you unregister: MyTrails keeps track of the area of all your offline maps, and computes the total area, excluding overlaps (the area of the union of your maps), which means that if the map you unregister overlaps another map, the overlapping area will not be refunded.
What happens if you make a mistake and omit to unregister it? You need to use our server to unregister it.
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if you do not yet have a FrogSparks account, create one from your device: MyTrails > Preferences > Accounts > FrogSparks > Register, which will associate the maps you have purchased from your device with your account.
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from your device or a computer, go to our self-administration server.
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once you’ve logged in, you’ll see the list of offline maps you have created, and you can unregister the map.