The new Garmin handheld GPS units with the “x” designation now offer removable microSD cards for map storage. Among the models with this capability are:
|GPSmap 60CSx||GPSmap 76Cx||GPSmap 76CSx|
|eTrex Venture Cs||eTrex Vista Cx||eTrex Legend Cx||eTrex Vista HCx|
|eTrex Legend HCx||Astro Dog Tracking||Rino 520 HCx||Rino 530 HCx|
The first four are very similar in their electronics and capabilities; I own the first on the list (the 60Cx), and it’s fantastic! The SirfStarIII chipset allows fast position acquisition with incredible sensitivity – I can get fixes in heavy tree cover and mountainous terrain that gave my old Garmin eMap fits. The HCx models also use the SirfStar III chipset. While not geodetic-quality, if you use any of the SirfStarIII units with some care it’s possible to achieve 1-2 meter real-time positional accuracy repeatably. And the microSD (aka TransFlash) memory cards allow for lots of room for Garmin’s uploadable maps, like the Garmin USA Topo or City Navigator series. I’ve seen 1 GB microSD cards for less than 15 dollars, and Garmin says that their units will support 2 GB cards (but not SanDisk Ultra II cards). Added 6/22/2009: Recent hardware upgrades to some Garmin units may have increased this to 4 GB, but there are apparently issues with some cards. But there are two drawbacks to these large-capacity microSD cards:
1. It appears as though the USB connection used for uploading map data is USB 1.1 at 12 Mbps, not USB 2.0 at 480 Mbps. Maximum transfer speed for a standard microSD card is on the order of 80 Mbps, well below USB 1.1’s speed. While not a big deal for the default 64 MB microSD card that comes with most of these units, filling up a 512 MB card using USB 1.1 can be time-consuming. For example, I have a set of 1300 MetroGuide and Topo maps that cover much of the western US and take up about 470 MB of space. Uploading these into my Garmin with a 512 MB card, even with USB, takes about 50 minutes: 10 minutes just to put together the map set index and data, and 40 minutes to upload the data to the GPS unit. If you were to upload a full 2 GB of data, it could take as longer than two hours! The read-write speed of a microSD card is 80 Mbps, which is about 6.5 time faster than USB 1.1, but about 1/9th the speed of USB 2.0, so it could benefit from a USB 2.0 connection.
2. There’s a limit of 2025 individual maps in a map set. For some map sets, like MetroGuide, you can cover the whole US easily without coming anywhere close to this limit. But combine that with a set of Garmin Topo maps, or some other map sets, and you could hit that limit easily. 2/08/2008: If you use a card reader, you can load more than 2025 individual maps, but your Garmin may not be able to read them all, leaving gaps in the coverage.
There’s an easy and fairly cheap solution to the upload speed problem. When you buy a new microSD card, it usually comes with an adapter that allows you to use it as a standard-size SD card (Garmin doesn’t supply one with its units, though). You can buy a USB 2.0 card reader capable of reading/writing to such a card for less than $10 shipped; just make sure it’s fully USB 2.0 compatible, and can take SD cards. If you don’t already have a large-capacity microSD card, you can get a 2 GB card from Amazon along with a compact USB 2.0 card reader for less than $25:
If you plug the microSD card into a card reader, Garmin’s MapSource software will recognize the card reader as a legitimate destination for uploading, and allow you to send mapsets to the card at a speed limited only by the USB 2.0 port and the read/write speed of the microSD card. In my case, using such a card reader to upload data cuts the total time, including indexing and creating the map set, from 50 minutes down to less than 15 minutes – nice!
But once you’ve created and uploaded such a mapset, and you want to use it again in the future, there’s an even faster way to get it onto your microSD card than using MapSource. The microSD card will show up as a removable drive in My Computer in Windows; open this drive and you’ll see one folder called “garmin”. Open that folder, and it will contain a single file called “gmapsupp.img”; this is the file that contains all of the combined map data that’s been uploaded. You can copy this file to your hard drive, and save it for future use. The next time you want to use this map set, just open up that “garmin” folder again on your microSD card, delete the old gmapsupp.img file, and copy the gmapsupp.img map set file you want to use into the “garmin” folder. When you put that microSD card into your Garmin and turn it on, it will take a few seconds for it to index the data, but then you’ll be ready to use that map set data. Copying over the gmapsupp.img file I created above from my hard drive to the microSD card took only about 4 minutes, because there was no need to run MapSource to index and assemble the map set. Double nice!
But you can also use this capability to increase the total number of maps stored on your microSD card to more than the 2025 map limit, although you’ll still only have access to a max of 2025 at any one time. First, break up the maps into multiple sets, each with less than 2025 maps. Upload one set to the microSD card, then open up the microSD card and change that mapset’s name to something else other than gmapsupp.img. Upload another set, and change its name to something else as well. Keep doing this until you run out of mapsets, or out of space on the microSD card. To enable your Garmin to use and display and of those mapsets, change the name of the mapset you want to use to gmapsupp.img. You can access these files to change their names either through the SD card reader, or by putting your Garmin into USB Mass Storage mode (available from the Interface screen in the Setup section) while it’s hooked up to the computer through the USB connection to make the Garmin act like an SD card reader.
One caveat: I’ve tried this only on Garmin map data that doesn’t require an unlock code. It should work on lockable map sets as well, as long as you upload them to the unit they’re unlocked for, but I can’t swear to that; let me know if there’s a problem with those.
All in all, handling the Garmin data in the microSD card this way could save you lots of time and effort.
Finally, if you haven’t updated your unit’s firmware recently, you should do so. The original units had a limited memory capacity for saving track data, but the updated software allows you to save track data directly to the microSD card, so you’re only limited by the amount of free memory available on the card. You can set this option in the Tracks => Setup Data Card Setup section; check the box next to “Log Track To Data Card”. Tracks logged here will *not* show up either on the display, or in the Track list, and you can’t download them using EasyGPS or other standard GPS utilities. They’re saved as date-stamped GPX files on the microSD card, so you’ll have to open up the microSD card directly from the computer and copy them over; either plug the microSD card into a card reader, or put your Garmin into USB mass storage mode to access these files, copy them over to your computer, then delete them on the microSD card to free up space for new tracks.