Actually, you're not understanding correctly. Firstly you need to accept that a map image file [*.img] is the fully compiled map which can be read and used by the device. It can also be read and used [to a limited extent] by BaseCamp [but not at ALL by MapInstall -MI makes images and doesn't read or use them in any other way]. So, to install maps on a device [i.e. create an image file] only MI is used, and the data it uses to do that is in the gmap folder installed in your PC [hence the term 'PC Install version']. The gmap folder data can also be read by BC, but it cannot compile/instal/send an image to the device, to do that it invokes MI, however to a casual user although they may appear to be 2 parts of the one program they are in fact 2 completely separate stand-alone programs. You can use MI to instal maps on a device or card without first starting BC, and BC cannot do that directly it must call on MI to do that job from the PC installed gmap data.

So in essence i think you've been confusing what can be done using an image in BC, and further not grasping that a complete working image can only be compiled from the gmap folder data using MI [not BC].

Now what you need do is download a PC install version [or just the gmap folder]. Run the installer to fully instal or just place the gmap folder according to your OS. See the links given previously. At the risk of Caty & myself repeating ourselves:
Quote Originally Posted by Neil View Post
................ For a tutorial, look to [Only registered and activated users can see links. ] and scroll down to 'Have you downloaded a PC map version (.exe) for Basecamp/Mapsource?' and 'Have you downloaded a Gmap folder ?'. BaseCamp has an initial pop-up video tutorial as part of the program and very good on-board help.
Quote Originally Posted by catymag View Post
Have you installed the City Navigator in your pc?

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Quote Originally Posted by catymag View Post
Basecamp reads your .img in sd, Basecamp supposes you have this .img already in your nuvi/sd, so it's obvious you can't split it with Mapinstall and install parts of this map again in nuvi/sd.
If you want to install a map with Mapinstall, you must run CN installer on pc and once installed, you'll be able to move the selected .img to your device.

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Quote Originally Posted by catymag View Post
I suggest you read again this thread and Neil's posts.
He explained you your Eu map is too big for your nuvi: it can't read it.
So you must install the CNEU pc version, select a part of it (less than 2gb) and send it from pc Mapinstall program to your sd.

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The image file on your nuvi is too big to be seen by the device itself. It can be seen by BC but BC can't do anything with it in the way you're wanting/expecting.