SiRFstar III reception under dense canopy

My wife and I went on our weekly mountain bike ride today, and of course we took our GPS receivers along for the ride!  I was kind of excited about it; we were going to ride a trail in dense redwoods that I had never been able to map due to poor satellite reception. But today I had my Garmin 60CSx along, which has the SiRFstar III chipset on board.

Now when I say dense, I do mean dense. Redwoods are actually a low biodiversity plant community; very little grows on the forest floor due to their dense shade. I've heard it said that native Americans here didn't like the redwoods -- that they are downright spooky. More likely it was just the lack of game and edible plants, but you get the idea.

The trail we rode, Manly Gulch, is as challenging as it sounds -- narrow and technical, with steep dropoffs. The photo at left is of me coming around a tight curve between two redwoods. The trail section pictured is a narrow perched run set between a cut redwood stump on the upper side and a retaining wall on the lower side.

But to make a long story short, the 60CSx and SiRFstar III performed admirably, as can be seen in the map posted at right. I've seen my 60CSx get a lock inside, and I knew it had greatly improved reception over the 60CS, but it was still nice to see it all work so well where it counts.

Comments

[Dan]

What sort of mount did you use for the 60CSx? I've been eyeing one to replace an ancient etrex, but the garmin bike mount looks like a loosey-goosey cradle instead of the clamped-on back the etrex series uses.

[Rich Owings]

Dan-

I used a RAM mount. Their catalog is hard to navigate by the way. I got mine from GPS City, which makes it easier to figure out which one to order. Also, if you have 31.8 mm handlebars, RAM mounts are harder to deal with. I had to use the Garmin mount on my wife's bike, and yes, it isn't as solid as the RAM. More info here...
http://gpstracklog.typepad.com/gps_tracklog/2006/07/bike_mounts_for.html

[Dan]

Wow, they make a lot of mounts. It looks like for mountain biking, you have a choice between the huge motorcycle version, and the "light duty" bicycle mount. Which did you end up with? Does yours have that big pivot ball, or do they have a more direct mount of any sort? Extra pivot points seem like a bad idea on the bike.

I may hold off a bit and see if there aren't any sirf-based etrex announcements at that trade show this week before I pull the trigger.

Thanks for your help!!

[Sam Curren]

I've been drooling over the 60csx since I first ran into it..

Anyway, that tracklog would make an excellent addition to a new trails site I'm working on: ActiveTrails.com
It's free, and will generate elevation profiles, topo maps, and a 3D trail view in Google Earth.

[Rich Owings]

Dan-

It's the light duty mount, which is rock solid IMHO. Measure those handlebars first though.

http://www.gpscity.com/item-ram/rap274ga12.htm

Rich

[Rich Owings]

Sam,

Cool site! And you have a trail in my neighborhood -- the Trestle Trail, which I have yet to ride. Hmm, that one goes on the list.

Sure, you are welcome to the Manly Gulch track. It includes a nice single-track approach, but I missed the single-track exit and had to grind up the road. I'll email the file to you separately.

[Mike]

Yep, a the SiRFstar chip is definately helpful in the thick canopy of Manly Gulch. Here's a link to the same ride recorded with a ForeTrex 201:

http://trail.motionbased.com/trail/episode/view.mb?episodePk.pkValue=1512

The reception wasn't too bad, I applied MB Gravity to clean up the elevation.

[Rich Owings]

Hey Mike, good to hear from you. You must have had good satellite coverage that day!

[Rich]

Hi all,

Thanks for the review. I'm buying one today to use while mountailn biking. I fear that it will get destroyed if I mount it on the handlebars (I tumble a lot). How will it do if I throw it in the top of my backpack?
Thanks,

Rich

[Rich Owings]

I've had good results in the outer mesh pocket of my CamelBak. It may do pretty well inside. Water (and any product containing water)and metal both block signals.