Re: GPSR for bicycling?

From: Kenneth Stagg (kstagg_at_harbornet.com)
Date: 06/17/04 

Date: Thu, 17 Jun 2004 06:17:35 -0700

On Wed, 16 Jun 2004 16:45:05 -0700, Peter <prathman@comcast.net> wrote:

> Ken Stagg wrote:
>
>> ............................................................... If it
>> proves itself it might replace my computer but it would most likely be
>> positioned as a computer for the stoker's position on the tandem.
>
> I've been using a GPS receiver (first a GPS12, followed by an eMap) to
> replace my bicycle computer for the last 5 years. If your tandem is the
> normal type then I'd expect the stoker's position to be a rather poor
> one for GPS reception. The human body is a very effective absorber of
> the GPS signals and mounting the unit on the stoker's bars on most
> tandems would result in much of the sky being blocked.

Our tandem is of the normal type but our positions on it are slightly
different which may help reception. My wife is taller than I am and her
handlebars sit a couple of inches behind and above my saddle. She also
has relatively long arms which places her body further away from her
handlebars (with a very long stoker's top tube) than is typical for
upright tandems. It still might not work well but it will be worth a try
if I get one for other uses.

> One solution is to use an external antenna which can be mounted in a
> better location.

This would also be an advantage to the Lowrance which I believe, at least
among the units that I was considering, is the only one that accomodates a
directly connected external antenna.

> Although it's somewhat higher priced, you may want to check out the
> 60c/cs. High resolution color screen makes it more readable, it
> supports a directly connected external antenna, and it has sufficient
> built-in memory for an extended tour.

I really wasn't sure that it provided enough memory. I was considering
that at that price I'd probably just go ahead and get one that used memory
cards unless there's something increadibly special about the 60cs. Or
maybe the 76cs with even more memory? How much memory does it take to
store "enough" detail for a long - say 4 week - tour?

>> One concern I have with the Garmin and Magellan units is number of
>> points in a track. How often is a point recorded?
>
> Most units let you specify this either by distance (e.g. a point every
> 0.1 mile), time (e.g. every 5 minutes), or auto. In 'auto' mode the
> unit checks how predictable your path is and puts in more points when
> you have many turns or are accelerating/decelerating. This mode is
> usually best since it records points where you need them the most and
> doesn't waste them on long straight streches of road. On my eMap
> recording in auto mode the 2000-point tracklog is usually enough for
> about a 100 mile ride. For longer rides I need to save the tracklog to
> one of 10 saved tracks but unfortunately these are somewhat lower
> resolution and lack timestamps to determine speed along the way.

I wasn't aware that saved tracks lost resolution. Given that, and my own
lazy nature, I'm even more likely to want to go with a unit that can use
external memory. The Meridians and the iFinder are sounding better all of
the time, though looking at the 60cs I see that its tracklogs are up to
10000 points.

And now Magellan is bringing out their eXplorist series, with the 300
looking very similar to the Vista. More choices to make :-)

-Ken

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