Electronics, Lighting, & Gadgets - Computer vs GPS

Bought a bike about a year ago (used) that has a Cateye computer on it. Works reasonably well, except that one of the wires came loose (or I guess that's what's wrong), and it now only senses the pedals, not the wheel any more. Thinking about chucking it and using a GPS instead - gives most of the info I want - speed, distance travelled, etc, and far less complicated to use as well. Also no pesky/ugly wires running up and down the tubes, not to mention the sensors. Anybody have experience with a GPS on a bike? They make special brackets to mount a standard unit (which I already have) on the handlebars.

I never really care how fast I'm going but I like to know where I've been and the rest of the data when I get into the house. I carry the GPS in my seat bag and check the information afterwards.

I have a Garmin etrex that I got five or six years ago. No maps, but it has waypoints. Handles speed, distance, compass as well as the data from GPS - elevation, time, sunrise/sunset. I got a handlebar mount last summer. I've used a bike computer before too.

GPS does everything a bike computer does, but I don't use it nearly as often. It takes some time to lock on to satellites, so it's no good for short trips. It's heavier to carry around if I lock up and go inside somewhere, and it's more valuable for someone to steal. It's not made to be a bike computer, so there can be a lot of awkward button presses to get to the numbers you want.

It's nice to not have to worry about a sensor or calibration though.

Since it doesn't have maps, the most I get is an arrow. If you've played GTA1 or 2, you know how that can mess you up. If you rely on it for directions, you can wind up on bad roads or dead ends. It's nice to have a destination, though - I can input latitude and longitude from Google Maps and it will point me exactly to that spot I saw on the satellite view.

Like CaptainCool, I also have a non-mapping Garmin Etrex.

GPS Pros:
No calibration.
Speed, distance, avg speed all available.
Backlight.
Can get you back to where you started, regardless of how lost you are.
Tracks can be downloaded into computer for analysis. (Requires additional software)

GPS Cons:
May require several minutes to acquire satellites.
May require several awkward button presses to get data you want.
No odometer function. (It does have a trip odo).
No auto start/stop function based on wheel motion.

If I'm going somewhere unfamiliar, I'll use the GPS. Otherwise, the Cateye on my roadie is easier. However, the computer on my commuter bike has recently failed, and I'm going to use the GPS instead of replacing it.

Bought a bike about a year ago (used) that has a Cateye computer on it. Works reasonably well, except that one of the wires came loose (or I guess that's what's wrong), and it now only senses the pedals, not the wheel any more. Thinking about chucking it and using a GPS instead - gives most of the info I want - speed, distance travelled, etc, and far less complicated to use as well. Also no pesky/ugly wires running up and down the tubes, not to mention the sensors. Anybody have experience with a GPS on a bike? They make special brackets to mount a standard unit (which I already have) on the handlebars.

I would use additional retention to supplement the bracket. My buddy hit a bump while going over a bridge and watched his GPS (that he had sent in for repair and had received a brand new back) fall into the river below and float away!

I have a garmin GPS with Mapsource program. You can build routes on the pc, and download them to the GPS in very few minutes. Then on the route the thing beeps .1 mile before each turn with arrow displaying turn direction, then beeps again at 100 yards. YOU CANNOT GET LOST.

If you just wander, you can upload where you have been via the trail left into the pc for future reference. My has vertical speed as well, altitude of course. It is also a good check for your given distances on your computer. It is far more accurate.

When I am alone in strange territory(INCLUDING $$ RIDES where I preload the route), or going with the group on a first time route I use it, otherwise it stays home.

For me this is one of the greatest toys available. I just cannot understand why any biker would want one without the full mapping functions and display. To each his own I guess.

GPS Cons:
May require several minutes to acquire satellites.
Usually not the case unless you haven't used the unit in a while. I almost always acquire a signal in under a minute.

No odometer function. (It does have a trip odo).
All of the Garmin handheld mapping units have this function. Both a trip odometer and a total odometer.


No auto start/stop function based on wheel motion.
The Garmin handheld mapping units know when you have stopped or are moving. It will also give you an moving average speed and a total trip average speed. And a moving time, stopped time, and total time.

Now there are places where a GPS isn't always going to be the best & a cyclometer is preferred. In dense forest, downtown environments and deep canyons, reception can be spotty. Also if you go into a long tunnel. But if you are on a road, 99.99 percent a GPS will give you a good signal.

If you ever download a ride into a mapping program from a handheld GPS, you'll never ride without one again. I merge all my rides together and I can view a map to see what roads I have never ridden on.

One other reason to use the Garmin mapping units is they have a computer screen that will show up to 8 different data at one time. I can view my MPH, avg speed, current time, odometer, trip odometer, distance to next, elevation speed and sunset.

Now a downside is if you buy a mapping unit, it will only come with a very basic basemap... Basic meaning only US highways, interstates, and major state routes. If you want specific streets for your area, you've got to buy their mapping software... usually around $100 more....

Since cyclometers are cheap, I would suggest perhaps using both.

Thanks for the help! I also have a basic Garmin Etrex. I bought it for biking and hiking, mostly to see how fast I had gone and how far rather than to map out routes. I usually have where I am going fairly well planned out before I go, so it is all I need. Interestingly enough, the GPS works on planes when help up right against the window - gives the correct altitude and ground speed.

On the same subject (kind of): Where do you think that GPS technology is headed? My feeling is that within 5 years or so, everyone (or everyone who has a cell phone now) will have something like a blackberry that incorporates GPS and mapping technology along with a phone and mini-computer.

This is WAY too much information for me. I use my GPS (low-end Garmin, I forget the model) very occasionally on mountain bike trips--I live near the Tahoe National Forest and you can still get lost in there sometimes. On the roadie, I much prefer a big-scale AAA map and a basic computer, just time, speed and distance. Dunno why everybody's griping about calibration, which is a one-time deal that takes about a minute, and I've never seen a use for a cadence function. If you can't tell how fast you're pedaling, you really need to pay more attention.

If really bored, you could buy a PocketPC phone that has a built in GPS.

My setup:

http://i21.photobucket.com/albums/b269/Chris_Lanctot/E-Bike/78d4.jpg

Magellan Explorist 500 on the left. And just in case you're wondering, that's the Bionx (eBike) controller on the right.

I love the Magellan on the bike for several reasons:

1 - Their bike mount is pretty sturdy. If you do crash, the GPS just pops out and bounces on the ground a bit. Not a problem for the Explorist series, they're pretty sturdy. Also the bike mount is easy to install and it positions the screen directly within your view.
2 - The 500 has a color backlit screen. So it's both useable in daytime and nighttime. Backlighting is adjustable.
3 - Built-in geocaching, if you're into that sort of thing. Mountain bikes are great for geocaching.
4 - Track logs are pretty usefull if you need to backtrack and for analysis afterwards. I especially like the fact that it even considers altitude.
5 - Routes are very useful. Every so often I discover some new trail deep in the woods so I simply convert that track to a route so the next time I want to go there I activate that route and follow the directions.
6 - ETA (Estimated time of arrival) is pretty usefull when following a route. That way if you get a cell phone call, you can tell your firends/wife approx. which time you'll be home.
7 - Points of interest are really useful. If you want to visit some location on a trail, just download the POI and map a route to it. Or if you suddenly find something really sweet, just log a POI and then you can download it into the computer later on. Every so often I see something special and take a picture. Then I'll plug in a POI into the GPS just to know where I took said picture. Usefull with google earth.
8 - Speed, distance, odometer (you can reset the odo), avg speed, time, ETA, distance to next waypoint etc. Many options you can select on the active display so it replaces a cycle computer for the most part. I only miss the cadence meter, the rest I can use the GPS for.

And since I have the Bionx, the speedo is built-in so I just glance to the right to see the speed. The GPS is about +/- 0.5 km/h off. Strangely enough, the explorist 500 is dead on with my car GPS (Factory navigation in my Acura). Maybe the Bionx is off? Not sure.

Don't forget that you can use a handheld Explorist for many other things; walking, taking mesurements, car, plane... yes... PLANE, boating (marking fishing spots) etc.

It's a very practical device and very well suited for bikes. Especially those who go deep in the woods.

Edit: Forgot to mention this: I purchased Magellan Mapsend Topo for Canada. So it's not just streets. There's plenty of POIs included as well as geopgraphical data like rivers, streams, trails, parks and the like. Best of all since it's a topo map you get altitude data. So you can actually see the outline of the mountain you climbing. if you suddenly see many altitude lines really close together in front of your position? Watch out... that means a near vertical drop.

For me this is one of the greatest toys available. I just cannot understand why any biker would want one without the full mapping functions and display. To each his own I guess.
Cost, maybe? Mapping units can cost as much as a decent bike. I originally got mine for mountain biking, so mapping wouldn't have been useful anyway.

Has anyone tried one of the GPS watches? They generally don't have map displays, but it seems like they would be good for keeping track of distance, speed, etc.

Usually not the case unless you haven't used the unit in a while. I almost always acquire a signal in under a minute.

A minute? Versus zero seconds for a standard bike computer? Perhaps I'm too impatient, but that's a long time to wait when the road is calling me.


Other downsides:

Cost (they typically cost 20-30 times what a decent bike computer costs).

Battery Life

Size (though some of the newer models like the Edge 305 are getting smaller).


I think the edge in terms of value still goes to the standard bike computers...but, this may change with the next generation of GPS satellites and receivers.

The best thing about a GPS period is accuracy and data....

http://biffstephens.motionbased.com

The cons for me are battery life and having to take it from your bike and download the stuff....in a few years they will be wireless in some way....

Not having a map is not that bad....personally I like the bread crumb function and it has helped me get home more than a few times....it is still handy....

I like my GPS and I am all for it...and mine take less then 30 seconds to lock on and I can ride while it is doing it...Garmin 305

garmin vista and legend are both good vista cx has color screens and maps and works good at night
you can change information to suit what you need gps is the only way to go plus it gives you elavation
just do it you will be happy

Cost, maybe? Mapping units can cost as much as a decent bike. I originally got mine for mountain biking, so mapping wouldn't have been useful anyway.


The $200 that my Etrex legend cx cost doesn't come close to the cost of my "decent" bikes, maybe if you added a zero it would be in the ball park of a couple of them.

Your assesment that mapping gps devices are not useful for mountain biking also puzzles me. I would find non mapping type gps devices useless. The maps are great out in the woods where there aren't any street signs and where you might want to know if your close to a road

I had the Garmin Gecko which is a very basic "get back" and waypoint marker with data readout such as elevation (fun on big declines), mph, trip time, avg's....blah, blah, blah. It costs approx 90.00 or so now if you can find one.

Now that I'm looking for something different I'll be looking at a wirless computer just for fun of it.

A minute? Versus zero seconds for a standard bike computer? Perhaps I'm too impatient, but that's a long time to wait when the road is calling me.


Other downsides:

Cost (they typically cost 20-30 times what a decent bike computer costs).

Battery Life

Size (though some of the newer models like the Edge 305 are getting smaller).


I think the edge in terms of value still goes to the standard bike computers...but, this may change with the next generation of GPS satellites and receivers.


Well, actually, if you are impatient, then, tun on the GPS early in your prep routine. Surely you don't just think about taking a ride and then are instantly upon the bike. Turn the GPS on as one of your first steps in preparing for a ride, and it will be finished acquiring as you mount the bike.

That is a pretty minor inconvenience in my experience. The Etrex doesn't come close to what I have spent on my bikes, and seems able to run forever on a set of AA's. Certainly not as long as a computer - they seem to run for a year on a set of batteries, but, I bet I get 18-24 hours out of a set of AA's in my Etrex, and I run rechargeable AA's, so, cost really becomes a non-factor.

It's really fun to approach an intersection (especially at night) where you can't get a good look at the road sign. Look down at your Garmin, and there is the street, name and all.

Also, if you have ever really lost your way on a bike (I have), it would be great to have a GPS where you just select the point you need to get to, and then follow the directions without having to ask, or worse, ride five or so miles on each wrong turn - those miles ad up pretty quick on a bike.

Caruso

That is a pretty minor inconvenience in my experience. The Etrex doesn't come close to what I have spent on my bikes, and seems able to run forever on a set of AA's. Certainly not as long as a computer - they seem to run for a year on a set of batteries, but, I bet I get 18-24 hours out of a set of AA's in my Etrex, and I run rechargeable AA's, so, cost really becomes a non-factor.

A GPS weighs a ton compared to a computer, if you happen to be a weight weenie. It eats batteries. My Cateye runs for years on 1 cr2032 button cell. 3 batteries in 12 years. The Cateye is tough as nails. and way cheaper too. BTW, if you have a wired computer, you can often pick up a new mounting kit with cable on ebay cheaply.

If all you want is speed and mileage, a computer is a lot better. If you want mapping and data logging, go with the GPS.

I would use additional retention to supplement the bracket. My buddy hit a bump while going over a bridge and watched his GPS (that he had sent in for repair and had received a brand new back) fall into the river below and float away!

Sad story . . . I guess it depends what GPS unit you have and how it and its bracket are designed. I have a Garmin Etrex CS that I received as a gift last Christmas. We ordered the accessory bike attachment bracket. It is very well made. The unit has since endured several hard crashes without coming loose and without damage. One of those crashes totalled the bike to which it was attached.

I would not be very happy with a set-up that wouldn't stay on the bike without a lot of extra doodads to hold it on.

Caruso

I have a garmin GPS with Mapsource program. It is far more accurate.

When I first received my Garmin, I had both the GPS and the Cateye mounted. During a switch in bikes, I rode for several months with just the Garmin alone.

I have since remounted the Cateye because I found that, while very accurate over time, the Garmin is slow to respond to changes in speed. I notice that, for instance, as I start a descent, the Garmin might get stuck at, say 15 mph and stay there long after I know for sure I have to be moving at 25 mph or more. Suddenly, it will sense the change in speed and jump straight to 25 from 15.

With both units operating simultaneously, I find that, at times, the two agree exactly. At other times, they do not (and I assume that the Garmin is faulty). For instance, I cannot count on the Garmin to get an accurate reading of maximum speed attained. It is just too slow to respond. Not that the number is an important one, but, I like to see how fast I can get her going on downhills. The other day, my computer registered 49 mph max on a downhill run, the Garmin only 41.

I cannot really watch these two units on an extended downhill . . . too dangerous, but I have watched long enough to see the computer smoothly run through the numbers as you accelerate while the Garmin has yet to sense that speed has changed more than a mile or two per hour.

I don't know quite why that should be . . . but it is.

For keeping stats on a ride, however, the Garmin is hard to beat. It can accurately track your route, distance, average speed, time stopped, altitude, etc.

The unit can be set to calculate routes for different types of vehicles/routes . . . bike/motorcycle/automobile/pedestrian, on road or off road, freeways/toll roads (yes or no), etc.

The Etrex does have an odometer . . . but, since I sometimes use the unit in my car, the odometer reading doesn't relate to my biking miles or the miles on any one bike.

I have found that both units will act strangely at times.

Last weekend I descended a hill and checked the max speed on the Garmin. It was 174 mph. I'm just about to congratulate myself on having the computer as a backup when I notice that its max reading was 96 mph - so, whatever messed up the Garmin also messed up the computer (the computer is a wireless model).

Anyhow, both are great toys, and I love having both on the bike (the Garmin is mounted to the bar, the computer to the stem (or whatever you call that part that clamps the bar in place). The mapping features (as described by an earlier poster) are a great plus.

I say, if you have room on the bike, use both.
Caruso

. . . one more thing . . .

The Garmin's back lighting is very cleverly designed, and I find it very useful.

I set mine to be on steady (so it doesn't turn off after 15 seconds or so). You can raise or lower the brightness. At night, I set mine on low, and can read the numbers with a short glance at anytime.

I find that turning on the Cateye's back light is awkward, and, once on, I cannot easily or quickly read the numbers through that uneven, green illumination. Additionally, the light goes out after 5 seconds or so . . . totally useless to me.

Caruso

. . . I have watched long enough to see the computer smoothly run through the numbers as you accelerate while the Garmin has yet to sense that speed has changed more than a mile or two per hour.

I don't know quite why that should be . . . but it is.
If you are in the forest, it is most likely due to poor satellite reception.


Turn the GPS on as one of your first steps in preparing for a ride, and it will be finished acquiring as you mount the bike.
The major benefits of newer GPS units (e.g. Edge 205/305) which use the SiRFstar chipset is a substantially reduced Time To First Fix (TTFF) and a much improved ability to stay locked onto satellites in poor coverage areas (forest, urban canyons, etc.).


I just cannot understand why any biker would want one without the full mapping functions and display. To each his own I guess.
I ride primarily for aerobic training in areas that I am very familiar with. As such, I have no need to see a map but the performance data from a unit like the Edge 305 is highly informative. If I were touring in an unfamiliar area, being able to see maps would be very useful and I would prefer to have an eTrex type unit. It really comes down to what information you are interested in and how you think you will use the device the majority of the time.

GPS doesn't come close to the accuracy of a properly calibrated computer.

By all means, use your GPS to find your way, if you're in unfamiliar areas, but use a computer for speed and distance!

So are you saying that the gps and your computer are not even close in information? Speed, distance, time moving, stopped, etc?

So are you saying that the gps and your computer are not even close in information? Speed, distance, time moving, stopped, etc?

Well, if you live in a flat desert, then they're probably pretty close, but in a forested, mountainous area or in an area with multi-storey buildings, the GPS is likely to be way off.

GPS is fine for navigation, but it's far from a precision tool relative to a bike computer.

I've found when I got the cyclometer calibrated, it's within 1 percent of the GPS and I live in South Carolina on mountain bike tires. If I get lazy and let the air pressure down in the tires, the cyclometer will be off up to 5 percent on the same rides. It's not the GPS that has changed, it's the accuracy of the cyclometer due to lower air pressure and tire wear. Once I calibrate the cyclometer again, it's within 1 percent of the GPS.

Two notes.

1) You got to property calibrate your cyclometer. That means measuring the tire distance and not just using a chart. And especially on thick tires, you'll have to calibrate every so often.

2) If you are in the dense woods, a canyon, or in a major downtown area, a GPS will not be nearly as accurate as a properly calibrated cyclometer. I wouldn't say way off, in downtown Baltimore this year, I estimated it was off by 3 percent after I plotted the course using mapping software.

There's no reason not to have both considering how cheap a cyclometer is. They compliment each other, not contradict each other. The one thing a GPS is when you follow the same ride is the consistancy. I always know when I am going to pass 3 miles on my ride (stop sign)... 5 miles on my ride (last mailbox before turning right to Lake) etc.

I consider 1% way off! 3% is not even in the ballpark. My bike computers are at ~0.3% (compared to true distances from a digital map released by our national mapping service) at worst, and usually better. And even then, you're getting good numbers for a GPS. Last time I walked through a built-up area with a GPS unit, it regularly "teleported" me 200-300 ft in a random direction, simply because GPS doesn't work well when you don't have an open sky around you.

I've found when I got the cyclometer calibrated, it's within 1 percent of the GPS and I live in South Carolina on mountain bike tires. If I get lazy and let the air pressure down in the tires, the cyclometer will be off up to 5 percent on the same rides. It's not the GPS that has changed, it's the accuracy of the cyclometer due to lower air pressure and tire wear. Once I calibrate the cyclometer again, it's within 1 percent of the GPS.

Two notes.

1) You got to property calibrate your cyclometer. That means measuring the tire distance and not just using a chart. And especially on thick tires, you'll have to calibrate every so often.

2) If you are in the dense woods, a canyon, or in a major downtown area, a GPS will not be nearly as accurate as a properly calibrated cyclometer. I wouldn't say way off, in downtown Baltimore this year, I estimated it was off by 3 percent after I plotted the course using mapping software.

There's no reason not to have both considering how cheap a cyclometer is. They compliment each other, not contradict each other. The one thing a GPS is when you follow the same ride is the consistancy. I always know when I am going to pass 3 miles on my ride (stop sign)... 5 miles on my ride (last mailbox before turning right to Lake) etc.

Garmin thought of this with the Edge series of their GPS enhanced training computers. The cadence/speed sensor option on the Edge 305 (Edge 305 + CAD or the Edge 305 Bundle) enhances accuracy by filling in data missed by the GPS. The Edge 305 also uses a barometric altimeter.

I've never been teleported 300 feet in another direction in a GPS in six years of using unless I'm in a deep bridge or tunnel. However, do you know what a 1 percent difference is? If your real speed is 10MPH a one percent difference is 10.1 MPH. Or on a 100 mile ride, it's 1 mile off. My GPS is well within 1 percent because I know almost exactly when it's going to reach 3.00 miles right around the stop sign. Considering that I don't ride in a perfect straight line, it varies by about 30 to 50 feet.

And what national map do you use? I own NGS maps, Delorme maps, Delorme Topo, and Mapsource national maps.

All of the Garmin handheld units will fill in any data missing by the GPS, it's not just unique to the Edge series.

I'll upload later today 100 rides I have taken along the same road that is covered in forest land since I can merge them all together. Out of the 100 miles I have ridden, not once has it varied by more than 50 feet.

GPS doesn't come close to the accuracy of a properly calibrated computer.

By all means, use your GPS to find your way, if you're in unfamiliar areas, but use a computer for speed and distance!
Current GPSRs that are waas enabled with SiRF III are 99% accurate. I've been using a Garmin Forerunner 305 5-6x week since december and the data is always reliable. My previous Forrunner 201 without SiRF III chipset had nowhere near this accuracy as it consistantly lost signal in tree cover. Same deal for my old magellan 315 handheld.

Has anyone tried one of the GPS watches? They generally don't have map displays, but it seems like they would be good for keeping track of distance, speed, etc.

For mapping (after the trip with a computer), the Suunto X9i (http://www.suunto.com/suunto/Worlds/outdoor/main/Product.jsp?bmLocale=en&FOLDER%3C%3Efolder_id=2534374302757908&ASSORTMENT%3C%3East_id=1408474395903593&CONTENT%3C%3Ecnt_id=10134198673986181&bmUID=1186414187494) is the only choice I know of. It collects and displays GPS waypoint data. The problem is, it's difficult to pack enough battery capacity in such a small space for the GPS. From what I've heard, in GPS use one needs to recharge the X9i at least once a day to keep it running. I believe Timex used to have similar "all inclusive" product, but I'm not sure if it's still in production.

Suunto, Polar and other manufacturers also have wristop watches that get GPS data wirelessly from a separate GPS receiver. The receiver has its own batteries, making the capacity problem that much easier to deal with. None of these watches (that I've seen) actually display the GPS position data, they just use it to calculate speed and distance. I don't know if one can download the full data from the receiver to a PC to map it as with the X9i.

If I needed HRM as well as speed/distance info, I might be tempted to look at these more carefully. As it is, I have a separate mapping GPS unit (Magellan) and a bike comp.

--J

You can go on and on how much you want about GPS accuracy, but the fact still is that it is nowhere near the accuracy of a calibrated bike computer. No matter how many acronyms or initialisms you throw at it.

But then, I'm pretty anal about having my computers as accurate as possible.

gpsblake, as my profile will tell you, I'm not in the US. What national map I use is irrelevant to you.

This has been a very helpful thread. I'm getting a new bike and was trying to decide whether I should hop on the GPS bandwagon or stick with a traditional computer. I was thinking that going with something like the Forerunner 305 would be useful since I also run a bit. However, after reading about issues with accuracy, reception in forests (which is where I do most of my running), and shorter battery life, I've decided that a traditional computer, with heart rate monitor, will suit me just fine for now.

Garmin thought of this with the Edge series of their GPS enhanced training computers. The cadence/speed sensor option on the Edge 305 (Edge 305 + CAD or the Edge 305 Bundle) enhances accuracy by filling in data missed by the GPS. The Edge 305 also uses a barometric altimeter.

I have the Edge 305 with the cadence/speed sensor and HRM. When I have the cadence/speed sensor working properly, the speed seems very accurate compared with my bike computer (a cheap one I still have mounted). A few weeks ago, I had a problem with the cadence/speed sensor, and the first thing I notice was inaccurate speeds when under heavy tree cover. Once I adjusted the speed magnet to where it was reading again, the accuracy is MUCH improved again. I guess the speed sensor fills in data when GPS coverage is poor, thus improving accuracy somewhat.