Memory Needed for a Small Section of Western North Carolina

Started by prglor, December 11, 2011, 07:17:11 AM

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Indrid Cold

Quote from: EagleBoy on December 13, 2011, 06:28:05 AM
And lastly, most vendors will ship cross border.  Even to North Carolina.  ;)
I added the US link for to your post above;););)


Thanks for the clarifications.  Pretty understandable when the terms are defined.  Like a word in a foreign language that means nothing until it's defined in your language.

I think your suggestion of going to a store and checking units out in person is a great idea.  Don't know why I didn't think of it myself except I've gotten into the habit of online shopping.  Thanks.  Will let you know what I decide to buy.


I see that eTrex 20 is available bundled with a 100K topo map.  Does this map cover the entire US?  How useful is a 100K map - I see that most maps on this site are 24K. 

Does the eTrex 20 have some form of compass or altimeter?  In reading some reviews I got the idea that this might be the case, although not as accurate as what's on the eTrex 30.


The eTrex 20 doesn't have a hardware compass or altimeter. It can figure out what direction you're heading from the GPS fix as long as you are moving. It can read your height from the GPS data also. These aren't the same thing as hardware that actually knows what direction you're pointing or what the barometric pressure is. I didn't find the compass all that useful on my 60csx, but the new triaxial compass on my Montana is very nice because it operates in any position and calibrates itself, unlike the old style Garmin compasses. I never use the altimeter, and you need to calibrate it at a known elevation if you want any accuracy.

The 100k topo's are a mixed bag. They can be very inaccurate, but it can be nice to have the whole country available when you need it. They also have DEM data that can produce shaded terrain, 3d views and provide elevation profiles for routes and tracks.

You can view them and see what you think here:


Thanks once again for the great information.  That link is super for seeing what the 100k topo map is like.  I looked up a similar topo map for the southeast 24k.  I'm not sure what advantage the 24k map has over the 100k one.  I zoomed down to the area around the fish hatchery in the Pisgah Forest near Brevard, NC which I'm familiar with and couldn't see much additional detail in the 24k map - maybe a few more marked trails. 

Interestingly, the 24k map does not show Road 475 in the Pisgah Forest which goes to the Fish Hatchery and many trailheads, whereas the 100k map does.  I learned that neither map shows POI's like the Ranger Station on Rte 276 just west of Brevard nor do they show most of the trails in the Pisgah Forest.  I can see where being able to overlay a scanned image of a map having these features on them would be immensely useful to me, so I am leaning heavily towards getting the eTrex 20 or even breaking the bank to get the eTrex 30.  What other advantages does the 30 offer besides a compass and an altimeter?  Being able to share data wirelessly with other people with similar GPS's would not be useful at this point in time.

If I were to get a bundle with the 100k topo map, could scanned images or Google Earth views be overlayed onto the 100k map?  I assume they could also be overlayed onto maps downloaded from this site or maps I create myself?


As long as they support Garmin Custom Maps it is east to DL images and georeference them to the base map.  I do this all the time by overlaying ski area maps onto the base map for my Dakota.


First, remember everything on the 100K maps are drawn at a 1:100,000 scale.  So they are not very accurate.  If you don't zoom in any more than .2 miles, they are fairly accurate.  But if you zoom in much more, they tend to be way off.  I bought the T model for the DEM data.  The maps suck but are good if you don't have anything else.  The topo maps on this site are much better-however, they tend to not have trails.

That's where My Trails comes in.  It is a transprent overlay map.  When you load it on your GPS with another map, it will show trails and POIs on top of the other map you have loaded.  In MapSource and BaseCamp, all you see is the trails.  My Trails has extremly good coverage for the Pisgah NF.  The Forest Service (who provided me all thier GIS data) has GPSed most of thier trails an they have extensive POIs like backcountry campsites.  My Trails has the Ranger Station/visitor center you mentioned (and the amptheater, bridges, info signs and campground).  It also has lots of FS roads including 475c which goes back to the fish hatchery.  If anything is missing or wrong, you can GPS it or trace it in GoogleEarth and I can add it to My Trails.


What is My Trails?

For that matter, what is the T model and DEM data?  Did you mean DAM(N) data?  :)


The T model includes Topo data.  DEM data is elevation data in a grid form, say 30m x 30m.  It can be used to generate a 3D view on your GPSr.


And My Trails?  Is that on this website or another one?


So now I'm convinced I need a gps that can handle both kinds of customized maps and has an external memory slot.  The eTrex 20 appears to be the lowest cost unit to get these features, but I'd kind of like to have a compass and an altimeter.  Let's say I can talk myself (and my wife) into my needing to lay out about $300 in order for us to hike without getting lost, is the eTrex 30 my best choice or are there other gps's in this price range I should consider?


I think the compass is really handy for geocachers and those of us who want to find other waypoints precisely.  I always forget to calibrate my altimeter.  It looks like the Etrex 30 is going for about $280 at REI, slightly less at Amazon, but if you are an REI member you get a dividend.  If you want a touchscreen you should look at the Garmin Dakotas or Oregons.


'needing to lay out about $300 in order for us to hike without getting lost'
If you need aGPSr unit for that, you should not be out there.  Always take a paper map with you and know how to use it.  An electronic device can fail at any time.


I didn't get my first GPS until I was almost 50 and managed to hike around fine without it.  :)

If you really must have the compass, I would get an Oregon 450. it is going for $260 right now at Amazon. Note that their prices can vary considerably from day to day, so you need to watch closely and be ready to buy when it drops. A more typical price has been closer to $300 at Amazon recently.