Cannot unlock maps

[Jimchance]

I have not used maes from here as a while. I got a new gps and moved my memory card into it. MY old GPS File DEpot maps show up on my map list, but the two I just loaded do not. The maps I tried to add are on the memory card as I can see them in File Manager. My GPS gives me a message "Cannot unlock Maps" on start up.

[Boyd]

The free maps on this site do not require "unlocking". There are, however, some maps that are listed here but you must go to another site to actually download. Some of them could be locked. If so, that would likely mean they could only be used on the first device on which they were installed, or only from the original memory card the map was provided on.

So... "it depends" on exactly what maps you're talking about. All of Garmin's own recent maps are locked in the same fashion. So perhaps the problem maps are actually commerical products from Garmin or a third party that have this kind of copy protection? For example, if you had a Garmin 24k topo on your old GPS and moved it to the new one, you'd get this sort of error message.

OTOH, it could also just be a bug in Garmin's software... it wouldn't be the first time for that. 

[Jimchance]

One is the New England topo and the other is My Trails. I believe the New England Topo was down loaded from this site. Less sure about "My Trails". IT seems to be some sort of overlay that you put on top of an existing map.

[Jimchance]

pulled the card out and loaded the topo map on internal memory. No problems.

[Boyd]

Cool.  MyTrails is a free map available on this site. It's just an overlay that must be enabled at the same time as another map.

How many maps are on the card? There's a limit to the number of "segments" that Garmin devices can access - these are the small "tiles" that make up the full map. This limit is reached long before you run out of space on a SD card. Impossible to be specific because it depends on the exact maps and GPS, but my experience has been that you will likely hit the limit with 4gb or less of map files. If you go over this limit, strange things may happen on the GPS. This is something Garmin really has not documented very well.

A limit of 4000 map segments is typical, with old devices only allowing about 2000 and a few new premium (ie: expensive) models supporting something like 10,000 segments.