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Get
A Fix - Mountain Biking with a GPS
By Crispin Bennett
This guide is intended to provide a brief overview of my
experiences using a GPS and PC software for mountain biking.
What is GPS?
A GPS (Global Positioning System) is a device that uses satellite
signals to calculate your precise position on Earth. The US
Government has positioned 36 satellites in orbit round the
earth, and the GPS receives signals from between 3 and 12
of these at any one time to calculate its location with an
accuracy of around 10 metres.
My GPS
I use a Garmin eTrex Venture GPS. I chose this basic unit
as it offers memory for 500 waypoints, 20 routes and 10 tracks
and was supplied with a serial cable for connection to a PC.
Although the basic Garmin eTrex would suffice, a PC cable
would still need to be purchased and the limited route storage
could be frustrating. My unit was purchased by mail order,
saving a considerable amount of money compared to my local
friendly outdoor shop.
Exposed to the elements, a GPS attaches to the handlebars
via an optional bracket.
This ensures it is visible and gives it a clear view of the
sky, but could render it vulnerable in a crash.
My GPS is attached to the bike handlebars via a handlebar mount. A Garmin GPS is weatherproof, so does not need to be protected from the elements. The GPS needs to see the sky in order to pick up satellites, so carrying it hidden in a rucsac is not an option - unless you just want to use it in emergencies. It works fine under clear plastic or when placed on a car dashboard. The unit can fail to get a signal if I am carrying the bike, when the handlebars tend to be next to my body, or when surrounded by foliage or a steep-sided valley. I use NiMH rechargeable batteries, and reckon to get maybe 10 hours out of a freshly charged set of two AA batteries. This is sufficient for a long day out.
A GPS IS NOT A REPLACEMENT FOR A MAP, COMPASS AND COMMON SENSE
Out on the hill, a route can be easily followed using the
GPS to guide you from waypoint to waypoint. The GPS display
can be customised to give information including OS grid reference,
distance travelled, speed, altitude, distance and direction
to the next waypoint. At the same time, a tracklog, which
is equivalent to a virtual breadcrumb trail is stored in the
GPS memory, so that the route followed is remembered.
A clear display shows my current speed, heading, together with direction and distance to destination
In use as a trip computer - with a choice of data fields
PC Software
I have access to Memory
Map Navigator and Anquet
software, offering 1:50,000 OS maps on CD-Rom. Both software
allow routes and waypoints to be plotted on a map and downloaded
to the GPS. Anquet has greater map coverage, and includes
height information, but uploaded track logs can not currently
be saved or examined. Memory Map Navigator allows track logs
to be saved and examined, but has reduced map coverage and
no height information.
However, for the RootGyde I use GPS
Utility (GPSU) - a fantastic bit of software that
is available for free on the internet. Maps can be scanned
in and GPSU
offers all the functionality of Anquet and Memory Map at
no cost. The route and tracklog files are easily decipherable text files and for this reason I use GPSU for generating
GPS files for the Stirling Bike Club RootGyde.
The free version of GPSU has limits on the size of routes that can be downloaded. To circumvent this, I split the longer
routes into two.
Planning a Route
To plan a ride, I sit down at the PC, fire up either Memory
Map Navigator or Anquet and plot a route on the map. The routes,
and associated waypoints, are then downloaded to the GPS.
Easy.
Riding the Route
After a hearty breakfast and a quick fettle with the bike,
the fun starts. The GPS guides us from waypoint to waypoint
as I ride the route with friends. We return to base several
hours later than predicted, a good day having been had by
all.
Where did we go?
After a hot bath and a cup of tea, I sit down at the PC and
fire up Memory Map Navigator. The tracklog is uploaded from
the GPS and I follow the tracklog on the map to see exactly
where we have been. The route and tracklog is also uploaded
to GPS Utility, this file being saved for the Stirling Bike
Club's RootGyde.
Contour maps are generated by copying the altitude information
from the GPSU tracklog into a spreadsheet (red contour maps)
or by plotting a path on Anquet (green contour maps).
I also upload photos from my digital camera and write a trip
report, which is then e-mail to Richard for posting on this
website.
Fame and adulation follow.
What you do
In awe of all the beautiful routes described on the Stirling
Bike Club website, you read the RootGyde
report and download the GPSU file to your PC. Using GPS Utility,
the route and tracklog is downloaded to your GPS and you go
out and ride.
Basic navigation would be done using the route information.
However, if you get lost or confused looking for a path, the
saved tracklog directs you to the track taken by me. You then
buy me a beer next time you see me.
What it looks like on the PC
A planned route to and from a waypoint is shown by the blue
line. An uploaded tracklog is shown by the red line. A short
break in the tracklog can also be seen - probably because
I had to carry the bike, obscuring the GPS with my body. This
image is taken from an upload to Memory Map Navigator. I have
not reproduced the OS map, thereby kindly saving Ordinance
Survey from suing my ass off and shutting the club website
down.
Enjoy!
© Crispin Bennett, 2003
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