Transfer Maps

If you have a laptop PC, use Garmin Express and download the maps to it, then update your GPS receivers. Even though both units have lifetime updates, if I recall correctly you can't simply copy the map file from one device to another as the maps have license keys that are tied to the device they are installed to. Each device needs to have a license key generated for it using Garmin Express.

But if its the same map on both Express doesn't need to download the map files again, just other files associated to a particular device, including the unlock files, so it'll use less data and be far quicker for the second device.

So express will automatically install the new map onto the 2nd device without internet connection?

I wonder, when I update one of my devices, a map file is written to my hard drive at the path C:\ProgramData\Garmin\CoreService\Downloads\Map. The folder is just short of 7GB. I am not selecting for the update to be saved anywhere except the Garmin device.

Is the device getting a map at approximately 7 GB and my Windows 10 PC also getting a 7GB write? Comprising in total near 14 GB? Is that significantly increasing the connect time?

Express needs an internet connection to check the eligibility of the device and to download the few files that are unique to that device ... at a minimum, the .unl and .gma files for unlocking and activating the map.

No. Garmin Express is caching the 7GB download, but it uses ProgramData as the cache location, which actually isn't a bad thing. If you choose to save the map files to the PC you eliminate the need of a move operation, which even at the speed of a NVME drive may take a few minutes.

Most of the time involved in a map update comes from Garmin using - depending upon device - either USB 1.0 / 1.1 or USB 2.0 for its transfers via cable. USB 1.0 only writes at 1.5 Mbps (Megabits per second), with USB 1.1 upping that to 12 Mbps. 2.0 is much faster at 480 Mbps, but the cable is your bottleneck when it comes to downloads. Eliminating the bottleneck is why I believe Garmin included WiFi map update support in certain models.

Exactly. Something my post really didn't make clear.

I've been maintaining two Garmin 3597 units with map updates for several years. I can affirm that updating the second one goes on much faster, as it skips on through the great majority of the overhead before beginning the actual download from PC to Garmin relying on the already downloaded stuff on the PC.

I have several different models of Garmin and can confirm this as well. But you have to chose download to device and computer. That way when the 2nd, 3rd, etc devices are plugged in Garmin only needs to see they are legit and then proceeds to update the map without the need to redownload the entire mapset.

I'm pretty sure that the place Garmin Express stores the installation files during a regular GPS update is different than where it stores the map for use with Mapsource or Basecamp when choosing the "install to computer option" of Garmin Express, at least for Windows PCs. The Mapsource/Basecamp map is removable from the PC by going to Apps and uninstalling a map (or going to ProgramData/Garmin/Maps and deleting files and folder) while the GE-installed update files, which are part of the normal Garmin Express "Install to Device," need to be manually deleted from ProgramData/Garmin/CoreService if you want to recover the disk space.

If you don't plan to use maps on the computer with Mapsource or Basecamp, you don't need to "Install to Computer" to have the files available for installation to multiple GPS devices. You will save space and download time by just accepting the default "Install to Device."

Correct, the Install to computer option installs a map to your computer for BaseCamp/MapSource to use. If you simply install to device then Express downloads map segments that it can then compile to send to your device. If you select to do both then Express does both, the files are stored in completely different locations.

...and really am not paying attention to such things. But I would hope we are agreed that if choosing to install the map to both PC and device Garmin isn't sending the map twice, right? That would be highly inefficient.

I don't know the inner workings of things, nor am I worried about saving space on my PC, I have about 6 TB to use with about half of that free.

What I have experienced is when I do not download to 'PC and the device', each device takes a lot longer to complete an update by needing to redownload the entire mapset with each new device I update. Watching GE when I download the first of my devices to both and then put the next device in, the downloading of the updated map takes a few seconds and then GE proceeds with the install whereas on the first device the download could take a half hour or more.

Don't know if it's coincidence as to my observation in my last post or not, but this has been my experience.

That's not how Express works. See https://forums.garmin.com/apps-software/mac-windows-software... and the comment from ExpressCustomerCare.

In a way it is. The map sent to your device is stored in a different place and in a different format to the map required by BaseCamp/MapSource. If you don't use either of those programs you should select Install to device only

Maybe not, but that's my experience regardless.

I'll take a wild guess and suggest that to minimize the installation times for devices #2, #3, etc. that you run Garmin Express' map update on your most full-featured device first, then do the older ones. That would maximize the chance that the first download would contain what the latter devices need.

It seems likely that running your first map update on a device that only gets 49 states will require more downloading when a later device receives all of North America or if the first device updated doesn't receive the largest JCV file.

One other consideration is that on the first download, installing to device and computer will take longer than just installing to the device, especially if Basecamp needs to be installed.

If you do download to device and computer but never use Basecamp, you will accumulate a lot of versions of CNNA on the computer so you could consider a visit every year or two to Settings/Apps, then uninstall the unneeded maps.

Although space is not a concern, I do delete maps that are two versions out, in other words I keep the current one and the one before it.

I have (and update in this order) these devices;
two DS61
two 2460
one Zumo 450
one Zumo 550

I use mapsource (I know it's no longer supported I just prefer it to basecamp) to update the two Zumo's since their internal size was to small long ago. I use GE to put whatever will fit on the Zumo and Mapsource to put the entire update on an SD card.

I've never taken out a stopwatch and timed all the updates and I realize since I am downloading to the first DS61 and PC that will take longer, but the rest go pretty quick as far as the actual download goes, the install fluctuates all the time.

Well I can't explain that, but given that the data downloaded to your computer that's compiled into a .img file to place on your device is completely different to the data downloaded for BaseCamp/MapSource, and saved in a completely different location, the information given in that link is correct and is certainly my experience.

I use Basecamp, so I never use the "Device only" option.

This raises another question. Do all Garmin GPSr's use the same map? For example, the Nuvi 3597 uses a green shading to indicate topography where the Drivelux models do not. Do they use different maps or just a different set of auxiliary files?

I have noticed the download time saving when updating multiple automotive devices but it does not appear to be the case with all my GPSr's. Handhelds and RV units for example take longer to update than my automotive units even after the first update is completed using the "save to computer" option.

It should also be noted that some newer devices update via WiFi and don't involve a computer.

It's a good question. My understanding is that the different models (at least the modern ones) do use the same .img files for the main map. I know in the past, I have successfully copied the map .img file from one of my newer devices like the nuvi 3597 to one of the older devices like my nuvi 755T.

As far as the differences in color/shading between different models, it is just the way the map data is interpreted and displayed by the device software. Some of this can be changed on models that support the .kmtf theme files.

For the nuvi 3597, the "topo" shading comes from an additional (transparent, I think) img file, gmapdem.img, that displays the shading along with the CNNA routable map. I pretty sure that I remember looking at dates once and saw that the gmapdem.img file isn't regularly updated with map updates, and may never have been revised.

At least I think that's the way I think the 3597 works, not having gone to my 3597 and looked at its files to see how accurate my memory is.

The DEM file isn't regularly updated, simply because topography is pretty consistent over time. The thing I have noticed most with my DriveSmart 65 and nüvi 65LMT compared to an older device like my 1300LM is the color scheme of their map themes. For example, in the newer units the orange color that on a 1300LM was for state highways is now given to the federal highways. The red color prominent in the older units for federal highways is apparently no longer used, at least on the default Garmin map theme.

Speaking of themes, our user Narvick created a couple that some folks prefer. See:

http://www.poi-factory.com/node/52412