GPS - Which Ones to Look For?

[utabintarbo]

FWIW, I don't get all the hate for the 305. Yes, it "prefers" the GPS over the wheel sensor. So? Where is it written that the wheel sensor is the "bible"? Can it possibly augment data when the GPS loses satellites? Sure, but I haven't lost satellite lock with either the 305 or the high-sensitivity eTrex in 2+ years of use. Also, what happens when the wheel diameter changes due to environmental or usage factors? Can the 500/800 compensate on-the-fly for these?

Face it, anything we can practically use on a bike will have some amount of variance from actual reality. AFAIAC, just about any high-sensitivity GPS that can drop trackpoints at a 1 second (or less) interval will give sufficiently accurate data for the purposes of the average bike geek (and likely even the highly anal bike geek). But if perfection is the bar, no one will win.

[nailgunn]

Accualy Yes my wheel calibration is always set to Automatic.
I have never heard my tire size recalibrate yet. Not sure what the recal tolerance is /would be. It takes @ a mile for it to valide wheel size.

I am not hating the 305

[rvd]

The Forerunner 305 is primary a Runners watch

Just replace the wrist strap with this and it is a Bikers GPS.

just about any high-sensitivity GPS that can drop trackpoints at a 1 second (or less) interval will give sufficiently accurate data for the purposes of the average bike geek.

If you read that piece by c0nsumer you'll see that 1-sec data collection without a wheel sensor significantly underestimates distance (and by consequence velocity) on twisty routes (i.e., MTB trails).

[c0nsumer]

FWIW, I don't get all the hate for the 305. Yes, it "prefers" the GPS over the wheel sensor. So? Where is it written that the wheel sensor is the "bible"?

My research shows that using GPS-only on typical local trails cause underreporting.

Can it possibly augment data when the GPS loses satellites?

Yes, this is exactly what it does. On the 305 if GPS sync is lost the wheel distance is used, just as on the 500.

Also, what happens when the wheel diameter changes due to environmental or usage factors? Can the 500/800 compensate on-the-fly for these?

The Edge 500 (and I presume the 800) does auto-calibration with about half a mile of essentially straight line riding with good GPS fix. After switching tire/wheel size, if my next ride won't take me in a straight line early on and the circumference is enough to make a major difference, I'll ride Milonas Drive between 21 and 22 Mile (here) and during the center straight section the unit will display "Wheel Circumference Calculated" or something like that. It only displays for a few seconds.

AFAIAC, just about any high-sensitivity GPS that can drop trackpoints at a 1 second (or less) interval will give sufficiently accurate data for the purposes of the average bike geek (and likely even the highly anal bike geek).

I wasn't sure of this, which is why I did the research that I did. I feel that this sufficiently shows that GPS only using the Edge 500 will misreport to a substantial degree when on typically curvy trails. To me that's enough to warrant augmenting the GPS data for recording distance while riding them. For roads/paths I don't think it matters much, since that's mostly straight lines which won't suffer nearly as badly.

[black2003ss]

I'm not as concerned with riding 20 or 30 miles and losing 10% on the report. I can live with that. What is unacceptable to me is riding a bike and being told by a GPS program (My Tracks in this case) that I averaged 66.78mph, had a max speed of 523.30mph, traveled 215.56mi in 1hour 18min. The most accurate data I have logged to date is in the car with my tracks. I did a test this morning and it said I went 15.76mi in 19min, which is about right for the route I drove. It still lost signal along the route and has "holes" in the route line.

Here is what I would like to do. I would like to load "planned routes" and know where I am going, just like on our Sunday morning rides. I would like to have an idea of average speed, max speed, and total distance traveled. I understand that I will have tolerance variation from the "aliasing". I don't think the GPS function is as important on something like a twisty trail like PLRA, Stony, ILRA, etc... I have a Cateye to tell me how I did on that trail. I really want the GPS more for actual navigation and to know where I am at and where I am going. My Cateye can tell me what my average speed was, the distance traveled and the time spent moving (it doesn't record when at rest). It would be nice to have all of that in one device though. I still think my phone is capable of doing most of this, I just need to figure out why it is so dang sensitive and off by miles. What the heck is happening that makes the phone think it is in the middle of Lake St. Clair when I am 50 miles away...I have no clue what does that.

[c0nsumer]

I'm not as concerned with riding 20 or 30 miles and losing 10% on the report. I can live with that. What is unacceptable to me is riding a bike and being told by a GPS program (My Tracks in this case) that I averaged 66.78mph, had a max speed of 523.30mph, traveled 215.56mi in 1hour 18min. The most accurate data I have logged to date is in the car with my tracks. I did a test this morning and it said I went 15.76mi in 19min, which is about right for the route I drove. It still lost signal along the route and has "holes" in the route line.

Here is what I would like to do. I would like to load "planned routes" and know where I am going, just like on our Sunday morning rides. I would like to have an idea of average speed, max speed, and total distance traveled. I understand that I will have tolerance variation from the "aliasing". I don't think the GPS function is as important on something like a twisty trail like PLRA, Stony, ILRA, etc... I have a Cateye to tell me how I did on that trail. I really want the GPS more for actual navigation and to know where I am at and where I am going. My Cateye can tell me what my average speed was, the distance traveled and the time spent moving (it doesn't record when at rest). It would be nice to have all of that in one device though. I still think my phone is capable of doing most of this, I just need to figure out why it is so dang sensitive and off by miles. What the heck is happening that makes the phone think it is in the middle of Lake St. Clair when I am 50 miles away...I have no clue what does that.

It's probably because GPS is super-low-power RF signal and positioning the receiver where it gets blocked by things (read: your body, metal parts, etc) can make it go all wonky. Couple this with the possibility of it falling back to cell tower or mobile network geolocation and you've got a recipe for weirdness.

When I use MyTracks to do GPS logging (it's what I used for the Addison Oaks map, actually) I ensure that it's got a as clear of a line of sight to the sky as possible by just having it in a plastic case and carrying it in my hand held out in front of me. Where do you keep your phone when riding, and where was it when doing the test in your car? I'd wager that if you put it in a small pouch on your shoulder (clipped to the strap of your bag) or in a pocket at the very top of your bag you'd have decent luck.

As a point of reference, when doing Mad Anthony this year I put my Edge 500 in a jersey pocket on my lower back so it could log HRM data. The GPS data was abysmal because the unit was on its side and had my body blocking half of the visible area. When mounted on the bars and facing/open to the sky it's quite good.

You may want to look into the GPS antenna design for your phone when figuring out where to carry it. It's likely designed so that it sees most of the sky when laying flat on a surface, screen up.

When the phone is positioned flat and screen up think of the antenna from that being being best at receiving a signal from a range shaped like an inverted bowl; a dome. This dome roughly matches the satellites visible from your point at any given time. If you put anything that blocks weak RF signals (read: your body, a bladder of water, etc) in that range you are cutting out that portion of the sky and the satellites in it. Once you are down to only a few visible satellites the accuracy will rapidly degrade. Couple this with multipath errors (think ghosting on an analog TV with OTA antenna) that can induce false delays in the signal and you've got a recipe for occasional mislocation. Couple all of that with how GPS calculates speed (simple distance vs. time between two recorded points) and you can see how occasional large jumps in speed or distance can happen, with occasional false recorded points.

Easy way to help mitigate all of this? Put your GPS somewhere where it has the best possible view of the sky... Like a car dashboard, maybe a front seat, handle bar, top of your pack, etc.

[black2003ss]

Where do you keep your phone when riding, and where was it when doing the test in your car? I'd wager that if you put it in a small pouch on your shoulder (clipped to the strap of your bag) or in a pocket at the very top of your bag you'd have decent luck.

I put the phone in a plastic ziploc baggie and place it in the top pocket of my camel back. It is the outer most and top pocket but could very easily be blocked by my body when I sit up at some points. And the material is somewhat thick. I never thought of the face or down issue and I may have placed it screen towards my body in the pocket. In the car, I had it on my lap the whole time.

I am thinking of trying one of these so that even if I can't "record" my track, I can at least have easier access to the NAV function to find out where I am...

http://www.amazon.com/Arkon-Handlebar-M ... 898&sr=8-2

OR

http://www.amazon.com/Arkon-SM427-Unive ... 898&sr=8-3

Might as well add A/C to the bike while I'm at it...

[rvd]

Here is what I would like to do. I would like to load "planned routes" and know where I am going, just like on our Sunday morning rides. I would like to have an idea of average speed, max speed, and total distance traveled. I understand that I will have tolerance variation from the "aliasing".

You can create courses using Garmin Connect and upload it to your device (from Forerunner 305 to Edge 800). You can do the same on your phone by creating a route in Google maps and then displaying it in either google earth or google maps. You can see your location and your position relative to your route as you go. To keep track of average speed, max speed, and total distance traveled you run a GPS tracker (e.g., endomondo) in the background.

[c0nsumer]

I put the phone in a plastic ziploc baggie and place it in the top pocket of my camel back. It is the outer most and top pocket but could very easily be blocked by my body when I sit up at some points. And the material is somewhat thick. I never thought of the face or down issue and I may have placed it screen towards my body in the pocket. In the car, I had it on my lap the whole time.

I am thinking of trying one of these so that even if I can't "record" my track, I can at least have easier access to the NAV function to find out where I am...

http://www.amazon.com/Arkon-Handlebar-M ... 898&sr=8-2

OR

http://www.amazon.com/Arkon-SM427-Unive ... 898&sr=8-3

Might as well add A/C to the bike while I'm at it...

Just don't crash. I bet the second one will lose the phone on rough stuff, too.

I actually went through a whole bunch of ideas like this for what I'd do to use my phone, and for a while had a typical computer on each bike. Eventually I found that the easiest thing was to get one Garmin Edge 500, a wheel sensor for each of my three regularly-ridden bikes, and just use that as my bike computer / data logger. It can do routing as well, but I haven't used it for that yet. I do keep heading on the main screen so I can see which way I'm going, as that helps me learn new routes.

I keep my phone in my pack and just pull it out if I want access to a map.

[rvd]

I am thinking of trying one of these so that even if I can't "record" my track, I can at least have easier access to the NAV function to find out where I am...
http://www.amazon.com/Arkon-Handlebar-M ... 898&sr=8-2
OR http://www.amazon.com/Arkon-SM427-Unive ... 898&sr=8-3

Just don't crash. I bet the second one will lose the phone on rough stuff, too.

This is a good one: http://www.wahoofitness.com/Products/Wahoo-Fitness-Wahoo-Bike-Case-for-iPhone.asp

[utabintarbo]

FWIW, I don't get all the hate for the 305. Yes, it "prefers" the GPS over the wheel sensor. So? Where is it written that the wheel sensor is the "bible"?

My research shows that using GPS-only on typical local trails cause underreporting.

Mine shows that the under-reporting is minimal when using 1 second intervals for trackpoints.

Can it possibly augment data when the GPS loses satellites?

Yes, this is exactly what it does. On the 305 if GPS sync is lost the wheel distance is used, just as on the 500.

I've yet to have this happen to me (as I stated above). Perhaps the capacitance of my huge carcass amplifies the signal.

Also, what happens when the wheel diameter changes due to environmental or usage factors? Can the 500/800 compensate on-the-fly for these?

The Edge 500 (and I presume the 800) does auto-calibration with about half a mile of essentially straight line riding with good GPS fix. After switching tire/wheel size, if my next ride won't take me in a straight line early on and the circumference is enough to make a major difference, I'll ride Milonas Drive between 21 and 22 Mile (here) and during the center straight section the unit will display "Wheel Circumference Calculated" or something like that. It only displays for a few seconds.

Does your tire circumference stay the same for the whole ride? I don't know for sure, but a minimal knowledge of physics implies that the air in the tire, as well as the rubber, will gain and lose heat according to usage and environment, thereby causing expansion and contraction, and therefore change the tire circumference.

AFAIAC, just about any high-sensitivity GPS that can drop trackpoints at a 1 second (or less) interval will give sufficiently accurate data for the purposes of the average bike geek (and likely even the highly anal bike geek).

I wasn't sure of this, which is why I did the research that I did. I feel that this sufficiently shows that GPS only using the Edge 500 will misreport to a substantial degree when on typically curvy trails. To me that's enough to warrant augmenting the GPS data for recording distance while riding them. For roads/paths I don't think it matters much, since that's mostly straight lines which won't suffer nearly as badly.

And as I pointed out in my second comment at your link above, I thought your methodology was, at the very least, incomplete. "Smart Recording" isn't, and basing any conclusion on that alone isn't either.

[nailgunn]

I look at it like this I tried the whole phone thingy.
Looking for a good app to export my GPX files to that is when I got a good track. I bought a handle bar mount system for my phone.. still iffy data.
I was also recording my calories weight blaaa blaaa 3 different sheets none worked together. All the time and energy I spent making it work I felt cost me more in time messing around.

I now have a Edge 800 and a Tanita BC-1000 body compensation monitor /scale.

Edge 800 communicates with the scale and stores all info as health information and uploads to Garmin Connect. I now have one application to work with. Takes less than a minute to upload activities and health info, I have reports, graphs and I can view summary information any month. I even add manual non garmin activities like my treadmill data.

For me time is money and the easier it is to record and track the more likely I will use it.
I had to buy the Garmin one year and just got my scale this year.
Just my two cents

[utabintarbo]

Here is what I would like to do. I would like to load "planned routes" and know where I am going, just like on our Sunday morning rides. I would like to have an idea of average speed, max speed, and total distance traveled. I understand that I will have tolerance variation from the "aliasing". I don't think the GPS function is as important on something like a twisty trail like PLRA, Stony, ILRA, etc... I have a Cateye to tell me how I did on that trail. I really want the GPS more for actual navigation and to know where I am at and where I am going. My Cateye can tell me what my average speed was, the distance traveled and the time spent moving (it doesn't record when at rest). It would be nice to have all of that in one device though. I still think my phone is capable of doing most of this, I just need to figure out why it is so dang sensitive and off by miles. What the heck is happening that makes the phone think it is in the middle of Lake St. Clair when I am 50 miles away...I have no clue what does that.

FWIW, given a choice, I'm a proponent of using the right tool for the job. Just as I probably wouldn't use a screwdriver to hammer nails if a hammer is available, if I want to gather GPS data, I'd likely use the best tool available to gather GPS data. A phone is rarely the best tool, though it can be adequate, if you keep it pointed correctly, and you don't crash, it doesn't rain, and the plate in your head doesn't get in the way. (Oops, was that a secret? ) The Edge and eTrex models that I have will survive rain and crashes and heavy leaf cover. And they will give you results that will likely be within 1% of reality (ie. close enough).

BTW, I use the eTrex Vist HCx that I linked earlier to guide us around those Sunday morning rides.