GENERAL: Garmin claims you can create Custom Maps in five easy steps (HERE). 'Your mileage may differ,' but using Google Earth to create Custom Maps was a time-consuming pain for this reviewer. For those interested in the highest-possible resolution aerial photo maps for Garmin's Custom Maps, the tool of choice is Global Ozi (about $20). This program will automatically download Google Earth maps and register them with .map files for Ozi Explorer, .mcx files for GPSDash, and .jgw (world) files for ArcView .tfw and Global Mapper .kmz maps. Unfortunately, G-Raster doesn't at present support GoogleOzi images.
Custom Maps are supported only by Gamin models: Oregon, Colorado, Dakota.GPSmap 62, and GPSmap 78 hand-held units.
The opening screen in GlobalOzi is centered in the Eastern Hemisphere.
To re-center the map to a location of interest, there are three position formats to choose from.
For North America, select "NW".
'Check & convert' will change the other two positions to agree with
The opening screen will only convert to 'close' to your input, since it moves in about 9Km desecrate steps.
-Also, if you want the opening screen to remember your position, check "Restore last position".
Notice that once you move to a selected position, the screen resolution changes from 27,608m/px to 34.7m/px (meters/pixel).
Also, the drop-down menu shows that the download resolution will be 2.17m/px -or about 18x18km.
Placing the cursor near the edge of the frame allows one to pan a half-frame at a time for additional downloads.
For example in Laramie, Wyoming, only a resolution of 0.51m/px is available.
Placing the cursor near the edges allows one to pan the frames a half-frame at a time. Download up to ten frames.
Each download will produce a .jpg map image, a .map file for Ozi Explorer, an .mcx files for GPSDash, and a .jgw (world) file to register the .jpg file for Global Mapper to create .kmz map images for Custom Maps.
NOTE: It is best to download frames into simple rectangles to prevent creating unnecessary pixels causing the Custom Maps to lose resolution in the Garmin units.
Since Garmin says the limit of Custom Maps is 100 tiles of no larger than 1024x1024pixels (104,857,600 pixels), theoretically only one GoogleOzi image of 8192x8192pixels (67,108,864 pixels) can be created without loss of resolution. However I've been able to create a .kmz file from 10 GoogleOzi high-resolution images without any noticable loss of resolution in a GPSmap 78sc. But this may be the limit.
WORKING WITH GLOBAL MAPPER:
Helpful Hints: Before loading the .jpg files into Global Mapper, it's best to run them through Photoshop Elements for Color Correction, Brightness (increase it by about 40% to make them more visible in the units (and Google Earth). It's also helpful to use Filter, Sharpen, Unsharp Mask (about 30%). Save the jpg images with the original filename.
In Global Mapper, open all the .jpg images at one time. Under GPS, select Send Raster Maps to Connected Garmin Device (and check Display on Top of Roads and Trails). At this point, I suggest you give the .kmz file a logical name and store it in a folder. Then you can upload the .kmz file to the unit at your convince.
Global Mapper creating a .kmz file from 10 GoogleOzi images
Now don't get lost out there -youall!