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Old 06-08-10, 06:59 AM   #1
mtalinm
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extra $80 for Garmin 705 instead of 605?

Bought a Garmin Edge 305 a few weeks ago and have a week to return it. love love love the device except for the lack of maps - not really a problem for my daily commute, but on weekend rides I don't always like to preplan/download the route, and even when I do I find myself deviating from it.

so I'd like to upgrade to a unit with maps, which means the 605 or 705. AFAIK the only differences are that the 705 supports a heart-rate monitor, a speed/cadence sensor, and a power meter

I've been using the heart-rate monitor with my 305 off and on and have found it mostly uninformative. Garmin doesn't use that info to compute calories burned (only on the 500, I hear), and it's pretty much always in the same range for me anyway. plus, I hate hate hate wearing the strap and especially putting it on in front of my riding buddies b/c I inevitably forget until I see the indicator on the Garmin. so that's not a reason to go for the 705

I also don't have much use for cadence, at least not now, though I suppose I could become interested in tracking this at some point. and I'm sure as heck not shelling out the cost of a bike for a power meter anytime soon

for me, I guess the only advantage of the 705 is that the speed sensor lets you use the Garmin when spinning on an indoor trainer - you would otherwise appear motionless to the GPS. I don't normally train inside as I find stationary cycling boring/unmotivating. I'd rather be outside in the cold with lobster mitts and booties

so...I'm thinking I'll save $80 and buy the 605 (and use the $80 to buy the maps). am I missing anything?
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Old 06-08-10, 05:05 PM   #2
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well, I guess it's not a lot to pay for option value. plus, I'm always suspicious that the GPS speed is a bit low; the speed sensor should make that more authoritative
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Old 06-09-10, 10:13 AM   #3
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You can get the wireless cadence/speed option for the 305...
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Old 06-09-10, 11:03 AM   #4
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Your logic seems pretty sound there. Only a couple of observations - you can determine whether or not its worth the $80. The 705 has a barometric altimeter built in to calculate elevation changes and grade. This is going to be more accurate than the 605, which relies on the GPS data alone (the difference here is that GPS may not understand the difference between the road and the terrain - so it will overstate your elevation changes when you cross a bridge, etc). The other thing is that sometimes, the GPS will lose its satellite connection. The 705 then records off the cadence/speed sensor. The 605 will just calculate from the point the satellite dropped to the point it restored. If you took a few turns in there, it will short-change you. This is a very rare occurrence, but it can happen.
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Old 06-11-10, 04:10 PM   #5
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It is all in what you want. Understand that none of these things are "needs". They are all "wants". It makes absolutely no sense to scrimp on a want. So, if you want it and can afford it go for the 705.

I bought a 705 with the heart rate monitor and speed/cadence sensor. I wanted to be able to transfer between bikes and use the navigation function on the bike and the car. The 705 does all that. Carry a few zip ties, a bit of old inner tube and a zip tie tool and the whole thing easily goes from bike to bike.

As far as I know no other product does all the things a 705 does in one package.

The only downside is that Garmin's owner's manual is, to use a charitable term, pathetic.
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Old 06-14-10, 10:13 PM   #6
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good advice latitude just placed an order for one. hoping I can get away with using the free maps on gpsfiledepot.com instead of shelling out $70 for Garmin's
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Old 06-15-10, 04:18 PM   #7
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Quote:
Originally Posted by mtalinm View Post
I'm always suspicious that the GPS speed is a bit low
There's really no way for this [the GPS speed to be low] to be true unless somebody is dancing their bike around rather than riding in a sort of straight line.

The GPS measures speed by figuring out where you are, comparing that to where you were a bit ago, and dividing that by the time difference. Either the algorithm used is wrong (which would be odd, as it's very simple) or your location would get more and more and more off over time.

Ultimately, GPS speeds are extremely accurate. The only problems are if your path changes significantly between data points (every second?) or you go into places with no GPS signal (like inside.) They're not so accurate at calculating altitudes, however, which is why the 305 and 705 (but not 205 and 605) have barometric altimeters.

I think the speed sensor is there for tunnels and for use on a trainer. It's calibrated automatically by the GPS when outside, so if there is any error in the GPS-calculated speed, it would also happen with the sensor unless you jumped through some hoops.

The barometric altimeter in the 705 helps it keep more accurate climbing results. I'd suggest the 705 over the 605 if just for that. And besides, if you decide to sell it, the 705 will be easier to sell. (Does the 705 package you're looking at include the HRM and cadence sensors? If so, you can sell them to get rid of some of the price difference.)

Personally, I've not found the maps in my 705 to be that useful. Yes, it has them, and I've got them up to date, but the interface is horrid, and the cpu inside is extremely slow and so it takes forever to tell it to give you directions somewhere. My $100 or so handheld GPS is far far faster and easier to use to get directions from. If I think I'm going to need the map, I bring the handheld GPS just for that.
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