GPS, biking,and trails

[Irulan]

Waterlili asked about my use OF GPS while riding.

I've got a Garmin Etrex Summit, which actually is my hubbys. He's on the skipatrol and the search and rescue group, so he's been using it for various functuins there.
I also have the National Geo. TOPO! software for WA, ID and OR.

I use it several ways for biking. First way is to "track" while I ride (think a crumb trail ala` Hansel and Gretel) which I then upload onto a map when I get home. This enables me to make an elevation profile so that I can see *exactly* how much climbing and descent I did.

I use these little maps to compile into a local map. Several of the areas I ride are riddled with trails but not mapped well. I like to see how thing connect and actual mileages vs. "guestimates", or how the GPS compares to my odometer. There will be slight variostions just due to how each device reads the terrain.

I also use the mapping software to explore... as in my previous post. I can "draw" a trail onto the map, and get teh approximate mileage and elevation gains. This is no substitute for actually riding the trail to see the condition of it. I can also mark key pointts ( waypoints) such as junctions or points of interest and then uplaod those into the GPS so we can locate them when we are out. I recall standing in a meadow last year in Idaho, we are all looking for a junction but it was so grassy and overgrown it took us 20 minutes to find it.

Here are some map samples:
Idaho elevation profile, from a trail map I drew (http://www.specialtyoutdoors.com/amb/bearpeteburgorf.jpg)

a trail I drew out to explore (http://www.specialtyoutdoors.com/amb/20miletrail.jpg)


now here are some examples of actual rides not just ones I drew out, these are tracks that I made and then uploaded into the mapping software:
Rocks of Sharon ride from my house.... (http://www.specialtyoutdoors.com/images/bike/rxsharonmap.jpg)

and the profile we uploaded after the ride:
3000' total gain, no wonder we were tired!! (http://www.specialtyoutdoors.com/images/bike/rxsharonprofile.jpg)


Whoa! this is way too much info! Waterlilli, you may be having trouble with your signal on runs if there is a lot of tree cover, or it may be how you have it set to track. These little units take a bit of practicel; I have really screwed up some of the maps I was **trying** to make.

oh, and a GPS is NEVER a substitute for map and compass skills.

Irulan

[DoubleLori]

I have two Garmin eTrex's and the mapping software too. I love them. I've found if you cover the same trail multiple times and average your tracks, you will get extremely accurate placement (the track will come out just about exactly the same as known mapped trails and roads on the National Geographic topographic map software). (I use both the Garmin software and the National Geographic software.)

[DoubleLori]

Satellite coverage does tend to be spotty at times. If you have a unit that displays the current satellite orientation, you will get a good idea of whether the tracking is going to be accurate or not. A large number of widely spaced satellites will give good triangulation and placement. If there are only a few that or close together or, worse, in a straight line, triangulation will be poor and the placement will be less precise. The deeper you are in a canyon, the worse it will get because only the satellites that are directly overhead will be in contact; you will lose the ones out on the horizon.

Sometimes the precision can change dramatically in just an hour or two. I've found many times on an out-and-back ride or hike that I will get good tracking in one direction and very poor tracking in the other direction.

The orientation of the GPS unit is very important. You have to have it out in front of you for the antenna to pick up the signals. Hanging it around your neck doesn't work. I hold it in my right hand while hiking or attach it to the bike with the bike mounts. I have both a road bike mount and a shock-absorbing mountain bike mount.

[Irulan]

hmm... I have a mesh pocket on the outside of my camelback and I have just been sticking the GPS in there. Mine doesn't have an external antenna tho.

Irulan...

DL, where are you we can trade maps!!