Import IMG files

You can't "import" .img files with BaseCamp; this has never been possible. You can put this file on the Montana, in the folder "Garmin".
Maps for the computer (to be used with BaseCamp) have a different format than the ones for on the device.
BaseCamp can however use maps from the device (when connected to the computer ofcourse), but only when they have the "visible" bit set somewhere in the file. These files haven't... That can be changed with JaVaWa Device Manager: http://www.javawa.nl/jdm_en.html

No, you can't import IMG (map) files into BaseCamp.

Many 3rd party IMG files (maps) are only intended to be used on a device.

That said BC can display IMG's (maps) on a device. If you don't want to leave your unit connected you can copy IMG's to a \Garmin folder on a removable drive (USB stick, flash card etc).

GMapTool allows you to add Family/Product ID's :)

Cannot find any settings on my Montana governing USB.

See http://garminmontanagpsr.wikispaces.com/Mass+Storage+Mode

I downloaded the first IMG from the page you linked to in your first post, put it on an SD card in my PC, and BaseCamp 4.3.3 didn't see it. It could be a Family/Product ID issue. I'm not sure.

PS: I have other 3rd party IMG's on the card that work fine.

Is this perhaps due to the Family ID? Do you know if there's a way to browse the MicroSD card from the Montana to be sure its reading the card correctly?

Almost certainly an Family ID/Product ID issue (is the SD card FAT32 formatted?). The Montana detects the maps on your SD card automatically; you don't need to/can't browse the SD card from the Montana.

Regarding the ID's: load the .img in GMapTool, pick a random number below 65536 for the Family ID (but not 2041 or an ID of one of the other maps you have), and set the Product ID to 1.

It could be a Family/Product ID issue.

Guess so, but it's also a visibility-bit issue.

That said BC can display IMG's (maps) on a device. If you don't want to leave your unit connected you can copy IMG's to a \Garmin folder on a removable drive (USB stick, flash card etc).

You can also use a SD card emulator. Make sure the emulated drive is indicated as "removeable". This avoids having to remove the microSD card or using the slower USB connection.

http://www.ltr-data.se/opencode.html/

I just checked some OSM maps I have and both FID and PID are 0 so that, by itself, is not an issue. I do see that the MS (MapSource) bit is set to 1. That needs to be 0 for BassCamp to recognize the maps. That said a device shouldn't care.

GMapTool doesn't alter the MS bit but JaVaWa Device Manager will.

I don't know about the "FID mismatch" error. I'll play some and see if I can make it work.

PS: These kind of issues aren't unusual with 3rd party maps. Garmin hasn't released the format of IMG files but over time some smart people have figured out enough to make them work. There are lists of Garmin map product FID/PID codes on the internet but they're likely to be incomplete. Garmin creates those codes so they're the only ones with a complete list.

Ok, I set the MS bit to 0, with JavaWa Device Manager 3.6, in atv_class1_trails_with_poi.img and BC now sees the maps. I get the same "FID mismatch" error with GMapTool 0.8.186.