GPS options for Devil Mountain Double

I'm getting ready for the Devil Mountain Double, and it's a good time to review GPS options for the ride. Back before Strava, GPS was a bit of fluff for rides like this, but the social networking + power analysis + segment timing of Strava provides so much value I wouldn't consider skipping GPS today. The following are the strengths and weaknesses of the various GPS options available to me:

Garmin Edge 500:

  1. Mine had the tabs snap off on me, so using it would require putting it in my jersey pocket. But I can borrow Cara's for the day.
  2. Battery life is likely adequate: it should last the double century if I start with a full charge. I will make sure auto-pause is on to limit battery consumption during rest stops (which will be minimal, but every bit counts). Smart sampling is unavailable due to the power meter (and I wouldn't use it anyway).
  3. It's light: only 58 grams without the mount, 66 grams with the mount.
  4. It's compact: mounted on my stem it won't be in the way.
  5. GPS accuracy is inerior to the other options.
  6. Altitude accuracy is good.
  7. Temperature is good.
  8. It reads my ANT+ power meter (with speed and cadence)
  9. It has navigation, but is prone to false "off course" warnings due to GPS errors. Fortunately I know the course. I will still use navigation, however, just to be sure.
  10. Mode buttons are super-easy to find and hit, since they're physical buttons on the sides of the unit.
  11. No text messages.

Garmin Edge 800:

  1. The tab appears to be more robust: I have heard of many examples of Edge 500 tabs snapping, but never Edge 800.
  2. Battery life is very marginal. I might risk it for 10 hours, but for the 14-16 hours this will take me, I can't risk it without a backup battery.
  3. It's heavy: 97 grams without the mount, 105 grams with the mount.
  4. I have an auxilliary battery I could use, which would add 84 grams + 9 grams for a cab = 93 grams bringing unit up to 208 grams with the mount. I could send the auxilliary battery, with my light, up to the top of Sierra ("Pet the Goat" rest stop) to spare having to carry it up most of the climbing. But it's one more thing which could go wrong.
  5. It's bulky: mounted on the stem it barely fits, but mounted on the handlebars it gets in the way. A BarFly type mount would work.
  6. GPS accuracy is excellent.
  7. Altitude accuracy is probably also good (I've not checked)
  8. Temperature is good.
  9. It reads my ANT+ power meter (with speed and cadence)
  10. Navigation is the best of all of the options.
  11. The display is difficult to read.
  12. Mode buttons are difficult to find and hit, since they're widgets on the hard-to-read display and there's no tactile feedback. When riding, attention available for this sort of thing is extremely limited, since most attention needs to be directed towards riding the bike.
  13. No text messages.

Garmin Forerunner 610:

  1. It mounts on my wrist, which is simple.
  2. Battery life is around 8 hours nominal: not enough for the double century, and not compatible with my auxillary battery.
  3. Mounted on wrist, it's 76 grams.
  4. GPS accuracy is excellent.
  5. Altitude accuracy seems to be okay, but I need to verify this.
  6. Temperature unreliable, since it's next to my wrist.
  7. It in theory reads my ANT+ power meter, but I've not tested this.
  8. I've not tested navigation. Here's a video.
  9. The display is relatively easy to read, especially since it's on my wrist so I can orient it as I need.
  10. The touch display is somewhat cumbersome, but simpler than the Edge 800, since it's so compact there's not room for much.
  11. No text messages.

HTC Incredible phone with Strava Cycling app:

  1. I don't have a mount, so it needs to go in my pocket.
  2. Battery life is at best 3 hours in the present state of the phone, down from perhaps 5 hours when the Android app was first released (due to battery fatigue). It may be acceptable with my auxilliary battery, but this is untested.
  3. 138 grams with no mount, 231 grams with my auxilliary battery and cable.
  4. GPS accuracy is excellent, from experiments.
  5. No altitude (rely on Strava to use Google data based on position).
  6. No temperature.
  7. It doesn't read my ANT+ power meter without third-party hardware.
  8. No programmed courses on app, but app plots position on Google map, which is clear and easy to read. This would be a navigation aid if I knew where I was trying to go but, for example, was trying to figure out if I needed to turn left or right.
  9. The display is relatively easy to read, especially since when held in my hand it can be tilted to optimize visibility.
  10. The touch display is fairly easy to use, since switching between data and maps uses swipes rather than widget hits.
  11. I can send email, text messages, phone calls, etc. I wouldn't take my phone unless I was using it for position recording, due to the weight and bulk.

Considering all of these factors, the Edge 500 is the clear winner. You really don't need to look further than the battery life. I've not tested the battery on my particular unit but previous Edge 500's have lasted for the double century distance, and there's plenty of Edge 500 data on Strava from previous DMDs. Using a bulky auxilliary battery is obviously undesirable.

It's curious Garmin, in releasing an Edge 510 which, from the numbers, suggests a successor to the Edge 500, went with someone closer to the weight, bulk, display, and battery life issues of the Edge 800 than the compact efficiency of the Edge 500. I find the Edge 500 much more suitable for events like this.

So how does my choice stack up? I did a search on Strava for riders who did the Devil Mountain Double (rides starting in San Ramon, extending over 300 km). I then took the first 20 and counted what they had listed for their GPS source. This included results from 2009 through 2012, with no obvious sorting order. Here's the result:

GPScount
Edge 50013
unidentified3
Edge 7052
Edge 3051
Edge 8001

So Edge 500 was the overwhelming popular result. It's clear the battery is up to the task, at least for these finishers. The older Edge 305 and Edge 705 also had some representation. And finally, there was a single Edge 800, so at least that unit had the battery power to survive the ride, but it didn't have any ANT+ Sport data and was set for "smart sampling", so these may have contributed to a relatively extended battery life. Three rides were listed as "mobile device" which means the data source was unidentified (so marked on the table). This can happen when loading a file exported from Garmin Connect, for example.

Comments

Nicholas said…
I had a fair bit of battery life left after a 12hr timetrial that I used my Garmin 500 for, autopause off (though stopped time was less than 2min), ANT+ power and speed.
April 24, 2013 at 8:08 AM
Post a Comment

Popular posts from this blog

Marin Avenue (Berkeley)

Image
On Saturday, I got an email from Tim telling letting me know that Murphy's Spring Classics was going to start up Marin Ave. I'd missed that. Murphy announces his courses the day before, and indeed it was already well into the night before when the course announcement went out. I'd skipped over the details, jumping straight to middle and end games. Marin? I laughed at the irony, because not long before when he'd told me he was choosing to repeat the Nifty Twn Fifty which we'd done together last year versus selecting Murphy Mack's Stage Mullett two-day, I responded I didn't think I had it in me to ride Marin Ave two years in succession. Well, so much for that. I was committed, so I went downstairs to swap my 11-26 cassette for my Recon 12-27. The name is easily overlooked: "Marin Ave" fails to strike the same impression as, for example, "Redwood Gulch" or "China Grade". But among those in the know, Marin Ave is infamous i
Read more

hummingbird feeder physics

Image
I couldn't figure out how the hummingbird feeder worked. Why didn't it overflow? Forces need to balance, of course. Neglecting surface tension, there liquid level is higher in the inner reservoir than in the feeding chamber, so there must be a corresponding pressure difference. Suppose the pressure in the inner chamber were zero. Then the column height difference would need to be atmospheric pressure / (density of liquid × gravity). But this is over 9 meters! Obviously the height difference is only approximately 1% of this. So the pressure difference inside versus outside is only approximately 1%. The inside is only slightly below atmosphere. So air is getting in. How? Does it diffuse through the liquid? If this were the dominant mechanism, it wouldn't take long for the pressure inside to go from 99% to 99.3%, for example, which should be plenty to push the column of liquid down in the inside chamber and thus push liquid out through the holes. It would over
Read more

Gallium Pro geometry

Image
On Caltrain yesterday, I was surprised to see among the usual set of commuting bikes a SRAM Red-equipped Argon Gallium Pro. The bike immediately stole your attention. The design was one which has been trending: clear-coated carbon with plenty of text detail so the viewer is sure to realize he's gazing upon the result of advanced, proprietary engineering and not at yet another paint job on the same old OEM frames being pumped out of the same old Taiwanese factories. But it worked: the bottom bracket area was huge, the downtube a large-diameter "inverted Kamm tail" design seemingly designed to maximize wind resistance, the top tube a broad, eccentric shape which screamed "vertically compliant yet torsionally stiff". All it lacked were the pencil-think seat stays Cervelo popularized, but this was a machine designed for stiffness over anything else. It seemed dramatic overkill, since the bike was small (the Argon "XS" I suspect). There wasn't muc
Read more