Garmin sat-navs. encrypted IMG file

I heard that some Garmin sat-navs will only work with an encrypted form of IMG file, and so the usual OSM + sendmap instructions won’t work. Does that problem ring any bells with anyone? By “garmin sat-navs” we must be talking about the nüvi range I guess, although there is also the discontinued streetpilot range and zumo for motorbikes.

I notice that there’s a few discussions about OSM maps on nuvi’s here on this forum (and not all complaining that it doesn’t work) so maybe it’s entirely untrue. Or maybe encryption is only a problem on some models.

Well I hope they aren’t encrypted or we not being able to cope with the encryption, because I just told someone it’s no problem to buy a Nüvi and use it with OSM. o_O

I think you messed something up here. There are reasons why a given map will not necessarily work on a particular device, but this does not imply that an entire range of sat-navs will be barred from using free maps. Here are some facts:

*** Locked maps** This is the type where the term “encryption” is most appropriate. Most commercial maps are locked and require a product key to work. This key is derived from the map id and serial number of the unit so that a given product key can unlock only one map for one specific device. If locking is not enabled, the map will work on any compatible sat-nav. There have been some commercial maps like Garmin’s MetroGuide which were sold unlocked.
*** Compatability** Sometimes a newer and better map format is defined that will (of course) not be supported by older units. One example is the NT format of City Navigator: These maps use a better compression and therefore require less memory. The newer sat-navs all support NT maps and are also backward compatible so that they can also load older non-NT maps.
*** Capability** Even if a map can be loaded successfully on a sat-nav, not all features might be available. For instance, some newer nüvis can display a shaded relief if available on a topographic map or 3D buildings that come with newer City Navigator versions.

Garmin has not published its .img format but some clever guys have reverse engineered most of it and made the information available. This is actually the reason why we can make custom maps for our Garmin units at all. Since it’s the old non-NT format and (hopefully) all current Garmin units are backwards compatible, they should work on all of them.

I use a (discontinued) StreetPilot c510 and this runs fine with Radomir’s maps. Currently, the limitations are not with the sat-navs, but with the availability of good Garmin OSM maps. But I know that quite a lot of people are working on the required tools.:slight_smile:

Good info :slight_smile:

Yes thanks for that. I guess it was probably confusion about locked maps which started that rumour then. So it’s reasonable to hope that an IMG file generated by mkgmap would be usable on the full nuvi range.