Cyclometer or Handheld GPS??
 

Im looking to get something for my bike that at least tells me my altidude along with speed , average speed distance blah blah... but Im wondering if a handheld GPS unit would be better. I like the idea of seeing on a display where Ive been and having a trail to look back on as well. But do GPS units display speed?

Yep

Keep in mind that a GPS works by using satellites. I love mine, but every once in a while, it'll blip and say my max speed was 400 MPH or something like that. In general though, it works well. It doesn't work as well if you use it amongst tall buildings and it doesn't work at all if you can't see the sky. I've found that I use it when I drive now too. I'm chronically lost. It's a cool toy.

Will it do cadence and heart rate? My preference is to have everything in one unit, though gps is not in the budget for quite a while.

Both?

http://www.garmin.com/products/edge305/Attachment 31526

I think what the OP is looking for is a bicycle computer that has a GPS built into it. Frankly I'm surprised Shimano has not developed a Flight Deck model of one yet. Give them time I'm sure they will.

I just bolt my eTrex to the top tube or handlebar. I couldn't care less about actually measuring cadence or heart rate at this point. The GPS tracks distance, time, average speed, top speed, current speed, and has a backtrack log and navigation ability to waypoints I've stored.


Fun stuff, but they're separate tools. A cyclometer can't replace a GPS if you need GPS features, nor vise versa.

GPS is accurate, at any given moment, to about 20 ft on average. That is, your reported position is anywhere within about 20 ft from the true position. This shifts back and forth as you move. In narrow streets with relatively little sky visible, you could easily appear to move completely opposite your true direction, because the error moves backwards faster than you move forwards! Not only that, but the error could shift between positions as far apart as 100-200 ft in a second...

GPS is fine for finding your way, but for precision work such as showing and recording speed and distance, it's not good at all. Unless you live in a flat desert with only a few very low buildings...

A cyclometer, when properly calibrated, is accurate in any condition, to about 0.3% or better. That is, the error in recorded distance for exactly 100 miles, for example, is only about 1500 ft or so at the most.

http://www.ja-gps.com.au/gpscomparison.html

Altitude is the complicated one, there are multiple ways each device calculates it.

Since a decent cyclocomputer only costs about $30-35 (i.e., Sigma BC1600 w/ cadence on eBay), why worry about it? Go buy one.:D

Agree. I had my Garmin Legend zip tied atop my Planet Bike cyclo-puter for yesterdays ride. Not for any particular reason other than I wanted to see if the two were in agreement on total mileage and average speed.

My plan is to drag the GPS along on the long meandering ride-abouts, where I find myself befuddled to where I actually am.

Unless they have a barometric altimeter, they're generally useless for elevation.

I've been using a GPS for years now. I have found they are very accurate most of the time and never need calibrating. I can switch the GPS to any bicycle I want without having to do a thing to it. Today's ride is an example. According to my GPS, I rode 23.36 miles. I then went to my Delorme mapping software, plotting out the exact route I rode today and used their software to determine the miles. 23.27 miles the software determined what I rode. That's pretty darn accurate.

Now in a downtown area with large skyscrapers or in a dense forest environment, the GPS probably isn't going to be as accurate as a probably calibrated cyclometer. But the key is PROPERLY calibrated cyclometer, meaning you take a ruler to measure your diameter of your tire rotation and use that figure, not the generic figure that the instructions tell you.

But there isn't a rule that says you can't use both? With a GPS you can download your rides to a map or use the GPS itself as a map. Cyclometers are very inexpensive and I used both on my tour in 2005.

I wouldn't say the altitude on a non-barometric GPS is useless but it isn't nearly as accurate as a probably calibrated barometric GPS altimeter. But if you got a low pressure system coming through your area and you don't calibrate the barometric altimeter, it isn't going to be accurate either. According to the manual, a barometric GPS altimeter should be calibrated every few hours.

Im going with both. Im keeping my current cyclometer and have ordered the Garmin Vista Cx.

Be prepared to shell out another $80 for decent maps.........*cough*bittorrent*cough*

Sure, in a flat area, with few and low hills, and no forests or tall buildings, the GPS is fairly accurate. Your close match was likely luck more than actual precision, though errors could average out over longer distances to some extent.

The cyclometer, on the other hand, has almost no sources of error if calibrated properly (which is easy to do, if the unit allows detailed settings). Just ride a known distance (straight street/road measured on a detailed map, or in a GIS) and adjust the distance per revolution setting to produce that distance.

Both. I have CatEye CC-CD300-DWs on both the road bikes, and a CatEye Micro-Wireless on the MTB; I have a Garmin Quest which I've used on all the bikes for just over a year (i.e. all of 2006 season, and from about the fall of 2005).

The Quest is so convenient; I've ridden centuries, metrics, long and short rides, all without reference to a single map whilst on the bike - well, OK, planned routes have to be set up to start with, but how else would you do it? Even without pre-loaded routes, the maps in the Quest are quite adequate for navigation.

I've found the GPS to be such a boon for cycling - it certainly beats stopping at every junction to read a paper map! Of course it would be almost useless if the DoD decided to switch on Selective Availability, or if the maintenance of the constellation of satellites was less than stellar… (so to speak…) :rolleyes:

- Wil

Yes, GPS serves extremely well as a wayfinding tool. For recording distance travelled, average speeds and so on, it's not so good.

Thanks, *cough*Ill do that as soon as it arrives*cough* As a matter of fact Ill do that right now*cough* *cough*thanks again*cough*

Not luck. I document and download every single ride I do. Very rarely is it off by even 1 percent. Now in all fairness, I do live in a rural, non-mountainous area but it is heavily forested. I guess if I rode around downtown NYC or along steep cliffs, it would be less accurate. The GPS is also great for average MPH, my unit always knows when I have stopped and will stop calculating a moving average speed and time moved.

But if I was really in need to be deadly accurate, I would get a cyclometer & calibrate it properly. But I find that being always under 1 percent is pretty darn good.

The only time I kick myself is the times I'll go walking for a geocache with my GPS while using it for bicycling. Or if I drive my car and forget to clear out the data. Then yes, it does mess up the data and I've got to reconstruct it from the GPS log taking out the distance and time walking or riding in the car.

Still a GPS is a great tool to have on a bike. And there's so many other things you can do with it besides bicycling.

I can't see them ever going back to Selective Availbity, too many public services and businesses now rely on GPS.

Well, it might vary with different devices (although I don't see why it should), I've found that the Garmin Quest is pretty consistent with the cyclometer on each of my bikes, usually to within 1 or 2%.

- Wil

That cough sounds bad. You should go see a doctor *cough* utorrent.

Nudge, nudge.

I did notice near the end of my tour that the cyclometer was showing a difference of 3 to 4 percent from the GPS unit while the beginning it was around 1 percent. I think it was the result of my tires wearing down and thus making the cyclometer more inaccurate. Air pressure probably also affects cyclometer accuracy, especially on mountain bike tires. The less pressure, the more tire that is constant with the road.

I probably should have done a wheel circumference measurement to bring the cyclometer back to being totally accurate but when you're riding 70 miles a day, it's not a real high priority.

Anyhow like I said with cyclometers being so cheap, no law says you can't have both a cyclometer and a GPS.

Pump your tyres up... :D

I've got both - an eTrex Vista Cx, and a Cateye Micro wireless. I pay more attention to the Garmin, since the numbers are bigger. I also use it to plot the elevation of the rides, too. The cyclocomputer I use essentially for overall speed and average speed.

the garmin vista has that you can get it at tiger direct for about 229.00 vista cx
gps is the only way to go
they are great

If the physical package fits your bars OK I'd bet you will be happy with that.
For training I use a Garmin Forerunner 301 and it is OK for that. For travelling
it can't compare to my old Garmin III+ with it's good antenna. Too bad the III+
won't fit on a truck!

Quick discussion of GPS accuracy: with 3 satellites strong and in view 2 dimension
mapping works and a 4th is required for 3D which provides altitude. I believe
that every vendors software will use more satellites but don't actually know that.
Imagine 3 satellites in a straight line at the zenith which are very close together.
Compare that with three satellites near the horizon as far as possible from one
another (120 degrees apart). The time signals and location from the first three
in a row will be very close together while the three in a triangle will be seperated
more. Any computational errors from the three in a line will be a much larger
proportion of their time differences compared to the big triangle satellite configuration.
Therefore the three in a row will have noticably more error.

Since the GPS system uses LEO (low earth orbit, not geosynchronous ~23,000 miles
away) satellites their congiguration in the sky above you changes all the time, as
does the accuracy. Both of my Garmins have a GPS screen which shows the actual
satellite configuration above you and something which indicates the error magnitude.

A rule of thumb that I've heard is that the altitude error is about 3 times the lat/long
error. I take that on faith but don't really know how it withstands scrutiny.

BTW, I've heard of people who are happy using their GPSs with Google Earth instead
of buying maps. (There may be a $20 US/year charge for the software that integrates
Google Earth with your tracks. I can't remember but I'll bet that Google can.)

My buddy hit a bump crossing a bridge and his GPS was knocked loose from the bracket and fell into the river never to be seen again. Pretty expensive gadget to be putting on a bike that could crash or otherwise lose it. Just food for thought. He sometimes loses signal and does not get accuracy that a computer would get.

Actually, four satellites is the minimum number of satellites required to give an unambiguous position. With three, there are two possible locations. Of course, if one of the two positions is outside the altitude limit of a commercial GPS unit, or below the geoid surface, then the other position can be assumed correct.

But, even in the best possible conditions, the average positional error is on the order of 15-20 ft.

You are riding a $1000+ machine that you could easily crash too. It's all about risks. My GPS has gone flying off the bike a couple of times. Each time was due to the fact that I did not latch it properly. Now I am more careful.

But I agree, if you just want something to keep track of miles etc. then a computer is the way to go. The batteries will last forever. I have a computer and a GPS. I only use the GPS when I want to go and explore a new area.

I am also thinking of buying a Garmin Edge. Not so much to use it to keep track of fitness but I write software for the Garmin that is used by other programmers. I would like to add the Edge fitness protocols to my software.