September 17th, 2006 | 
I admit it, I’m a data junkie. I’m a firm believer in the fact that you can’t improve what you can’t measure. So, I measure everything I can – it’s much cheaper than getting professional help with my obsession. In cycling, my favorite activity, there are loads of things to measure in the hope of improving performance – power (wattage), heart rate, speed, cadence, ascent/time, elevation, temperature, wind speed, etc. I’m constantly on the lookout for tools to help me capture this data. For a few years now, I’ve relied on my trusty HAC4 cycling computer to collect this information. This spring, though, Garmin delivered its second generation of cycling GPS devices that looked to add even more information gathering capabilities to my cycling experience. I had to have one.
The Garmin Edge 305
When combined with the included Garmin Training Center software (runs on your PC), it is a nice data gathering system that lets you capture data on speed, cadence, ascent/descent, elevation, HR as well as drawing a map of your journey using Garmin’s own mapping software. When combined with Garmin’s MotionBased online service (free for basic use), you also get a very nice implementation of Google Maps to show your ride route.
HR vs. Elevation from Garmin Training Center
Because of an injury earlier this year, I haven’t gotten in nearly as many miles as I usually do. I did, however, have a chance to use the Edge 305 in Europe for a week (without HR or cadence) and on several rides in the last few weeks (used as a whole system). Here are my observations:
Pros
- Very small device for so much functionality
- GPS locks onto satellites quickly (uses new SiRFstarIII receiver)
- No wires!
- Atmospheric altimeter – previous devices used GPS triangulation to calculate altitude which was usually wildly incorrect. This is much better, although is never completely accurate (my HAC4 was much better at this)
- Speed sensor takes over for GPS in measuring speed when GPS loses signal – required for the type of rides I do where many of the streets are densely tree-lined
- Stores track and elevation data so that you can use it to race against yourself or just use it for navigation (no visual map, just the path)
- Configurable displays – a huge number of choices for what data is displayed on each page of the display
- Garmin Training Center and MotionBased are very easy to use with a quick and easy USB connection between your PC and Edge 305
Cons
- Heart rate measurement issues – you can’t see it in the graph above, but my heart rate was, apparently, >240 bpm for a while. I have a high max HR, but it obviously isn’t that high.
- When the GPS is blocked and the unit is relying on the speed sensor, it seems to be reading the speed a couple of MPH too low. This may be a calibration issue – it judges the diameter of the wheel with a GPS reading.
- Both my HR strap and my speed/cadence sensor were DOA out of the box. After no response from Garmin customer support when I sent multiple emails, I stuck it out on the phone for a while and they agreed to send me new units. These worked as advertised.
- Batteries – the batteries in my HR strap and speed/cadence sensor were dead when I got them. The battery in the speed/cadence sensor has drained on me twice in my limited use already. This thing clearly suck a lot of power. Expect to replace them often (standard CR23032 batteries)
- Head unit battery life is not great – about a century worth. Depending on how you use it, I wouldn’t expect more than 8 hours at the max.
- MotionBased doesn’t accept an upload without GPS data – can’t capture information for a ride on a trainer, for example. Garmin Trainer Center works fine for this.
- No temperature (minor nit – MotionBased looks temp up when you upload)
While the cons outnumber the pros, I still like this device. It’s not hugely better than my HAC4 was, though. Of course, if you’re in to the GPS data, there is no comparison – there are loads of things you can do with the GPS data that simply wasn’t even available on other devices. Consider the price, which is high, along with your real need or desire for GPS data as part of your data-gathering before you jump to this unit. It’s cool . . . just not a slam-dunk.
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Interesting that your previous GPS had problems with altitude – I use a Garmin 100 (actually, a gift from you…) and use it *primarily* for altitude and find it fairly accurate – usually within 20 feet (I check it on summits). Of course, it has to sync with four satellites to do that, so it works best above treeline. Brad has a 300-series and it seems to do a good job with the absolute altitude even at low elevations, but the “net elevation gain” calculation is overstated – it must be counting the GPS fluctuations as real up and down.
By my figuring they should have both atmospheric and GPS altitude – this way the atmospheric altimeter could get synchronized with air pressure conditions whenever the GPS gets a strong reading, but you have the continuity of the atmospheric reading most times.