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  1. #1
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    Real GPS verses Phone GPS

    I've been using an Android and iPhone 3 to record my rides and then upload to Strava. There is a really twisty loop nearby that is generally considered to be 11 miles when measure via traditional wheelbase cycling computers. Both of the phones put it as just over 10 miles. My assumption is that the GPS sampling is just too infrequent or inaccurate.

    Will a real GPS work better? If so I may get one of the Garmin Cycling Computers otherwise I may get a Garmen eTrex 20 to be used for bikepacking, etc and keep using the iPhone for rides under 5 hours (max iphone battery time in my experience)

  2. #2
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    better than the phone, not as good as a wheel sensor. on the plus side, most of the cycling units (and quite a few of the newer handhelds that are ANT+ compatible) can use a wheel sensor.

  3. #3
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    I think if you are on the bike more than once a week, the dedicated GPS is the way to go. It offers many features and does most of them really well.

    My Garmin 800 is just turn it on and ride. I locks sats in under 30 seconds in a new area. I can't tell you how many times I've heard from my buddies, "Humm, I guess I was not locked on at the begining of the ride" or "i guess I lost reception through there"
    Lead by my Lefty............... right down the trail, no brakes.

  4. #4
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    GPS only updates once a second, the lag through the phone makes errors (phone polls repeater; repeater tells phone the coordinates). We (maybe me?) ride around 20 ft/sec, so all those little errors are turned into bigger errors. Oh BTW, the team I worked with spent 6 billion of your tax dollars on the GPS system. Use it proudly; and smile.

  5. #5
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    Huh? The phone doesn't get coordinates from any repeater, the phone receives the same GPS satellite signals that a handheld GPS does, and calculates the position once a second.

    You are confusing GPS reception with 'cell tower triangulation' which is not accurate at all, using the cellular signal strength and delay to approximate a position (not GPS signals).

    The only other thing that Cel towers sometimes do is provide 'assistance' to the phone GPS receiver (A-GPS) by providing some of the satellite data directly to the phone via a cellular connection instead of waiting 30 seconds to download that same packet of data from the GPS sats.

    The general reason that phones perform poorly with GPS is that their antennas are generally not optimized for GPS, instead they often have a multi-band antenna (which doesn't do any band really well), or if they do have a dedicated GPS antenna they don't have a sufficient ground plane to be highly sensitive and accurate in challenging reception conditions, like a dedicated handheld GPS can.

  6. #6
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    Phone GPS is good enough for me in the Mid Atlantic region and also worked well enough on the outskirts of places like Cortez, CO, Red Lodge, MT, Moab, UT, Jackson Hole, WY, etc. Not as accurate as a Garmin however carrying a single device is preferable for my minimalist needs.

    I use Cyclemeter on iPhone 5 (log to dailymile and less often to ridewithgps) and log 3-4 rides per week. Compared to the peeps with wheel sensors, my mileage is off by ~8% and the ride maps are good enough for my purposes.

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    I got annoyed by the inconsistencies of the phone based apps (I used android and iphone versions). I was riding along side a friend with a Garmin GPS and coparing each ride on Strava and it was silly how different they were. I ended up buying a Garmin Edge as soon as I could afford it.
    It seems that the GPS does not update frequently enough on the phones, however, the iphone was much more accurate in ideal situations (weather) than the android version.

  8. #8
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    If money allows, better Real GPS

  9. #9
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    I'm using Everytrail app on a Motorola Defy+ Android 2.3 phone. The Endomondo app I used before locks in quicker (<20 secs) but it doesn't have the camera function of Everytrail where you can take photos along the track. My only gripe with the phone based GPS is when I go through a highly urbanized area surrounded by 20 storey plus buildings, the tracking gets handed to the nearest cellsite which looks like I suddenly flew like Superman across a building faster than a speeding bullet. Otherwise, I'm happy with the GPS enabled camera function of the Everytrail app.

  10. #10
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    ...highly urbanized area surrounded by 20 storey plus buildings, the tracking gets handed to the nearest cellsite...
    Not exactly - the GPS does not derive a position from the cel tower. What you are experiencing is multipath reception where the GPS signals bounce all around the building surfaces and the GPS has a hard time differentiating between the real (direct) signal and the same signal arriving later because it is being reflected by all those large surfaces. A good GPS has a multipath algorithm that can choose the real signal and reject the delayed signal.

    Remember, the fundamental principle that GPS works on is speed of light to determine distances, so if the GPS picks the wrong signal (delayed) to use for the solution then the position can be way off...

  11. #11
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    I am not sure how this happened, but I am using my blackberry and GPSLogger to record my rides an upload to Strava. One day I was riding down to a museum with my father in law. I turned on the GPS to log the ride mostly to show him where went etc. So we ride to the building and I forgot to turn off the GPS logging as we went inside. I had it in my camelbak and inside the building it actually tracked all my movements. I only noticed this later when I down loaded the ride. So I was getting GPS signals inside building. From what I know about GPS this should not work as GPS is line of sight so I can only assume it was cell tower assisted at that point. I would not say the track it left was inch perfect, but it did correlate with my general path surprisingly well.
    Joe
    2003 KHS Alite 4000 26" Hardtail - XC, All mountain, blah blah blah.. I just ride.

  12. #12
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    Quote Originally Posted by JoePAz View Post
    I am not sure how this happened, but I am using my blackberry and GPSLogger to record my rides an upload to Strava. One day I was riding down to a museum with my father in law. I turned on the GPS to log the ride mostly to show him where went etc. So we ride to the building and I forgot to turn off the GPS logging as we went inside. I had it in my camelbak and inside the building it actually tracked all my movements. I only noticed this later when I down loaded the ride. So I was getting GPS signals inside building. From what I know about GPS this should not work as GPS is line of sight so I can only assume it was cell tower assisted at that point. I would not say the track it left was inch perfect, but it did correlate with my general path surprisingly well.
    the gps sat signal can penetrate some buildings sometimes.

  13. #13
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    Quote Originally Posted by fishbum View Post
    Not exactly - the GPS does not derive a position from the cel tower. What you are experiencing is multipath reception where the GPS signals bounce all around the building surfaces and the GPS has a hard time differentiating between the real (direct) signal and the same signal arriving later because it is being reflected by all those large surfaces. A good GPS has a multipath algorithm that can choose the real signal and reject the delayed signal.

    Remember, the fundamental principle that GPS works on is speed of light to determine distances, so if the GPS picks the wrong signal (delayed) to use for the solution then the position can be way off...
    Thanks for the clarif...Does that happen to a "real" GPS device like Garmin?

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    Quote Originally Posted by Gundam168 View Post
    Thanks for the clarif...Does that happen to a "real" GPS device like Garmin?
    it can, but dedicated GPS receivers are better able to process multipath signals. basically, what you see on your cell phone GPS is similar to where dedicated GPS receivers were 10yrs ago. Sensitivity is better, so you aren't going to drop the signal as much, but the accuracy is pretty similar.

    What's worse about the accuracy issue is that there's quite a lot of variability from one phone to another, and also quite a lot of variability from one app to another (every app processes the raw GPS data from the phone in some way or another, but they don't all do it the same way) so it's really hard to say with any certainty what phone/app combos are going to produce the most accurate, most consistent results. plus, when it comes to phones, you can buy an external bluetooth GPS receiver and improve the GPS performance of all of the apps on your phone because you are bypassing the lower quality integrated GPS hardware with a better quality GPS antenna and chip.

  15. #15
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    Quote Originally Posted by NateHawk View Post
    it can, but dedicated GPS receivers are better able to process multipath signals. basically, what you see on your cell phone GPS is similar to where dedicated GPS receivers were 10yrs ago. Sensitivity is better, so you aren't going to drop the signal as much, but the accuracy is pretty similar.

    What's worse about the accuracy issue is that there's quite a lot of variability from one phone to another, and also quite a lot of variability from one app to another (every app processes the raw GPS data from the phone in some way or another, but they don't all do it the same way) so it's really hard to say with any certainty what phone/app combos are going to produce the most accurate, most consistent results. plus, when it comes to phones, you can buy an external bluetooth GPS receiver and improve the GPS performance of all of the apps on your phone because you are bypassing the lower quality integrated GPS hardware with a better quality GPS antenna and chip.
    Thanks for the info. That;s why I noticed, that tracking seems better (more close to the road) on my cheaper Huawei Ideos U8150 (600 MHz) than on my Motorola Defy+ (1GHz) using the same app. I hope smartphone manufacturers could show measurable info on what GPS hardware they use so as customers can make an informed choice.

    Quote Originally Posted by NateHawk View Post
    the gps sat signal can penetrate some buildings sometimes.
    So that's why even if my GPS smartphone is in my pocket or even inside my scooter's compartment, it can still pick up GPS signals and continue tracking.

  16. #16
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    I used my iPhone 3gs then 4s for mapping for a long time, then switched to an edge 500 garmin as i had problems with the signal dropping out in valleys leading to weird results on certain trails

    edge 500 completely fixed the issue (with no wheel sensor) and I have never had a problem since on any trail

  17. #17
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    I use my iPhone (each newer released model seems to be more accurate than the previous one) and am currently just on the iPhone 4. I find it works extremely well. In 4,000 miles of riding this year I can only remember two rides where I had to manually edit a few GPS data points to get the correct ride.
    With the money to spend, I would go with a dedicated GPS for sure and would expect better results (as has been reported by most users) but I'm quite happy with my setup.
    I use MotionX and have found that different applications have better bad GPS point filtering than others and MotionX seems to put out some good GPS data compared to my experience with endomondo, strava and everytrail.

  18. #18
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    I stick to my SGSIII but soon gonna buy real standalone GPS device from Garmin . Much better choice than any phone with gps built in .

  19. #19
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    Quote Originally Posted by GlazedHam View Post
    Will a real GPS work better? If so I may get one of the Garmin Cycling Computers otherwise I may get a Garmen eTrex 20 to be used for bikepacking, etc and keep using the iPhone for rides under 5 hours (max iphone battery time in my experience)
    The most important aspect of a gps is the chipset. I think the latest and greatest chipset is SiRFstarV. Earlier chipsets would drop out a lot, especially if your in a city surrounded by buildings. The latest chipset will be more accurate and determine locations a lot quicker. The good thing about SSV is that it uses cell towers for WiFi signals, which in turn leads to better satellite reception when surrounded by buildings.

  20. #20
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    Quote Originally Posted by broadwayline View Post
    I used my iPhone 3gs then 4s for mapping for a long time, then switched to an edge 500 garmin as i had problems with the signal dropping out in valleys leading to weird results on certain trails

    edge 500 completely fixed the issue (with no wheel sensor) and I have never had a problem since on any trail

    This..on both MTB and ROAD rides, the Droid X2 would skip all over the place putting a real damper on the end of my rides to see it would cut off anywhere from 5-30 miles at times.

    I gotta early xmas gift from the wife..a Garmin Edge 500 and K-Edge mount..first ride today with was a 66 mile/5,000 foot elevation road ride on my Tarmac in the boonies/canyons to a lake and it recorded perfectly. No skips...no issues...PERFECT!

    Ive seen the iPhone work well to record, and my buddys' Galaxy S3 works well too...but my luck was hit and miss..I'm a def believer in a dedicated GPS..

  21. #21
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    Quote Originally Posted by SV11 View Post
    The most important aspect of a gps is the chipset. I think the latest and greatest chipset is SiRFstarV. Earlier chipsets would drop out a lot, especially if your in a city surrounded by buildings. The latest chipset will be more accurate and determine locations a lot quicker. The good thing about SSV is that it uses cell towers for WiFi signals, which in turn leads to better satellite reception when surrounded by buildings.
    It doesn't get the wifi signals from cell towers, it can use wifi OR cell towers to augment GPS (it receives GPS, GLONASS, Galileo, and Compass sat signals).

    Next-gen SiRFstar chips go beyond GPS for positioning - GPS

  22. #22
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    Another thing to consider is whether you have a nice phone or not. If you wipe out, it's safe to say that a bike specific GPS will have a better chance of survival than an iPhone. Plus, these bike computers also have a plethora of other functions that a phone doesn't like temperature.
    Will someday be living in Alaska with 2 pooches

  23. #23
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    Quote Originally Posted by Muffinhead View Post
    Another thing to consider is whether you have a nice phone or not. If you wipe out, it's safe to say that a bike specific GPS will have a better chance of survival than an iPhone. Plus, these bike computers also have a plethora of other functions that a phone doesn't like temperature.
    A plethora of temperature functions.

  24. #24
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    Quote Originally Posted by Gundam168 View Post
    A plethora of temperature functions.
    You can also add maps, your riding route, track your elevation, measure your heart rate, train towards goals, and check the pressure. In addition, phones don't work in the same range of operating temperatures as bike computers. The battery life is also longer than a phone. It just makes more sense to me to get a bike GPS rather than use a phone.
    Will someday be living in Alaska with 2 pooches

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    I can play my dying elk ringtone on my smartphone and leave it on a tree to distract the bear chasing me.

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