Newbie question re DRGs

[gatoruss]

Hi, I am new to this site, digital maps and GPSr.  I am about to pull the trigger an purchase a Garmin GPSr - Oregon/Dakota or Colorado - but that decision is a topic in an unto itself!  

I am planning a trip at the end of the month to the US VI - St John to be exact.  I plan to travel around the island and to do some hiking, etc.  I thought it would be a good idea to see what maps are available for St. John.  On this site, I found this list of maps http://www.gpsfiledepot.com/maps/country/vi.

The "US Virgin Islands Topo" looks promising.  If I understand the information correctly, I can download this map and load it on my Garmin thru MapSource.  But according to the features matrix, this map does not have trails.

The "United States territories & protectorates" indicates that it does show trails, but the information page states that:

These are USGS Digital Raster Graphics (DRGs) of the United States territories and protectorates plus the British Virgin Islands. For use with Global Mapper, MapWel, Moagu or any other GIS program.

Can someone explain what I would need to do with the downloaded file in order to use it on my Garmin - or point me to a link/tutorial that would explain the process.  Note, I understand that may likely be an involved and complex process, so if that is the case please excuse my ignorance - it is not my intention to waste anyone's time

Thanks!

[Seldom]

The US Territories and Protectorates Zip file appears to be scans of USGS quadrangles.  You could print it on paper or incorporate it into a raster based map (Beyond the scope of this answer). Windows will unpack the Zip.  Then use something like 7Zip to unpack the RAR. 

[gatoruss]

The US Territories and Protectorates Zip file appears to be scans of USGS quadrangles.  You could print it on paper or incorporate it into a raster based map (Beyond the scope of this answer). Windows will unpack the Zip.  Then use something like 7Zip to unpack the RAR. 

Could I use something like Garmin Custom Maps or Moagu/G-Raster to convert into a raster based map?

[Boyd]

Yes, the Garmin custom maps feature is intended for raster based imagery. I have a few examples here: http://www.gpsfiledepot.com/maps/byuser/282/

The format is limited in terms of size however. My own experiments have shown that the largest area you can cover with a USGS 24k topo is about 19 miles x 19 miles. This assumes imagery sampled at 10 feet per pixel. When sampling at lower resolutions you can cover larger areas, but map details become hard to read.