>Have any of you folks used a GPS/GIS receiver to map or plot your bike rides
>or favorite routes? For those of you who may not be familiar, GPS stands
>for Global Positioning System, basically tracking your whereabouts with the
>use of a network of satelittes. GIS is Geographic Information System which
>can store, manipulate, etc information and display that info graphically.
>I'd like to plot some bike paths/trails/rides here in central Massachusetts
>and then be able to view them in 2D and 3D (include changes in altitude).
GPS is great for locating yourself on a map that has some known coordinate
system (Latitude-Longitude, UTM, etc.) For example, it was quite helpful
during walks in Scottish bogs last year. But that's a different topic :) I
used a Garmin GPS-45, which has much to recommend it. It's small & light, and
it runs >10 hr on penlight cells. Current price at West Marine, Palo Alto, is
under $400. For $150, you can get a kit for PC download, but there are
cheaper alternatives if you look around a bit. I copied some software from
Compuserve, but haven't tried it out yet.
All in all, it's useful enough that I plan to take mine on a tour to France,
where the map is full of back roads that go every which way and are likely to
be poorly marked.
GPS currently runs in a mode referred to as "Selective Availability," (SA)
which means that its accuracy is degraded if you don't have access to DoD
codes or extra differential-GPS equipment. Under these conditions, the
accuracy is about 100 m, which is good enough to identify an intersection, but
not to tell if you are in your front or back yard. :) Even under changeable
weather conditions, the altimeter cyclometers give much more accurate altitude
than +/- 100 m, so the altitude function is almost useless.
The GPS-45 stores waypoints, particular places where you stop and key in an
ID name. You can prepare a line-segment map from these, but it won't have
great detail. For more detail, you would have to download continuously, which
would mean taking the computer on your bike as well! Because of SA, straight
roads might well come out looking wavy.
BTW, the inexpensive GPS receivers aren't super sensitive. A tree-lined
street is likely to cut off access to some of the satellites that are
nominally in view.
Hope this helps.