I didn't have any luck with the importing instructions for assembling and converting Open Street Maps.
But this method does work, and is easy. There are pre-built maps available to download:
* Get a 4GB sdhc memory card. The Garmin manual says 2GB is the maximum, but it's been increased.
(You might be able to fit the 500mb map on your original 705 drive if there's enough empty space. I haven't tried it.)
* plug your 705 in as a usb device. You'll have two mapped drives. One is the Garmin itself, the other is the sdhc card. Create a folder on the 4gb drive named "GARMIN". I added a text file named "4gb card.txt" just so I know which mapped drive I'm looking at.
* determine your latitute and longitude. Google "latitude and longitude" and pick your location off a map. For instance, Ohio is about -84 west and 39 north.
* daveh generates installable maps every few months, in different sizes and areas.
* see the daveh readme on selecting which map. He says his 2000mb maps will fit on a 2gb card, but they don't quite fit. The 1000mb ones will fit on a 2gb card easily, and the 2000mb on a 4gb card.
* The 1000mb -82 to 158 covers West Virginia east to Europe. The 500mb -93 to -85 covers Kansas City to Indianapolis for example.
To locate a longitude, use itouchmap.com/latlong.html
, and at the "Show Point from Latitude and Longitude" enter latitude 40, longitude -83 to see where the 1000mb -83 to +158 map starts, for instance.
The maps all have the same detail, just a larger area on the bigger maps. And they all seem to be the same speed for panning and zooming.
* download the map you want, and save it on your computer. It'll take a while. You should try the 500mb map for your area if you are in a hurry.
* copy it onto the GARMIN folder on your 705 4gb card. This is really slow for me, it takes a few hours to copy a 2000mb map. Copying files to the Garmin 705 is way, way slower than copying to a separate sd card reader.
* rename it to be gmapsupp.img. You can have other maps downloaded on the sdhc card, but only the map exactly named gmapsupp.img is usable by the 705. You can rename the current gmapsupp.img back to 1000mb--etc and rename a different map to gmapsupp.img if you want different coverage or to try a different map.
Keep the gmapbmap.img where it is already, on the 705 mapped drive. This base map is used if you zoom out too far, or pan off the edge of your downloaded map. And keep all your tcx and gpx files on the 705, too. The 4gb card is only for the maps.
* I like to click the "Safely Remove Hardware" icon on the Windows Tray before unplugging the 705.
Boot your 705 and see the maps!