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Just got a Garmin Etrex 20. What maps do people suggest for good topos for the Sierra Nevadas, National Parks, Inyo, etc in California/Nevada areas?

I've heard a bit about the Nat Geo maps, but there seem to be a few of them. Wondering if someone could suggest/clarify the "right" one(s)? The Garmin Mapsource 24k National Park ones are popular.

Second, is there a good source that describes how to properly load maps onto an SD Card? Everything I read just says "it's easy" but doesn't really explain anything.

Thanks ahead of time, looking forward to testing this thing out next weekend!

All I can offer you is that the Nat Geo 1:24K is very good and I reccommend getting it in a format you can load onto a hard drive and view with a big monitor. The Garmin mapsource stuff I have seen is less detailed/sophisticated than the TOPO (Nat Geo). I read some not so positive reviews of the SD card thing but I have NO experience myself. I know you can buy the TOPO maps already in SD card format from Nat Geo. Viewing the map on that tiny screen seems less than ideal but it could be good navigating in your vehicle. I use the Nat Geo CD rom maps at home but in operation, I am still stuck on paper maps purchased from the USGS website along with an older Etrex just to provide position. GJW

The National Geographic maps will NOT load into your gps. They are for your PC only.

go to www.gpsfiledepot.com for GOOD free topo maps of California, and all other states. These are better than what Garmin sells, and they are FREE. These maps will load into your GPS.

The only other maps I would consider are Garmins's BirdsEye maps. To get these you use Garmins free PC/mac based BaseCamp software. For $30/year you can get all the high res, color satelite photos you can download. You can also get Garmin's 24k USGS topo maps for $30/year too. These are as good as the National Geographic maps, and they will go into your gps.

Read the tutorials at GPSFileDepot

Download BaseCamp or MapSource from the Garmin site; this is how you get the maps from your computer to your GPS. Often Garmin says nothing at all about this process in the documentation for the GPS.

I have found one 24k quad from GPSFileDepot that was off by about 200'; it was an area out in the middle of nowhere. Those folks are doing the map conversion for free, and if there's a error in the data supplied by the USGS, they may not have the time to catch (let alone fix) the error.