How can you tell how good or average a GPS is?

Discussion in 'GPS Technical Discussion' started by mb1280, Feb 12, 2021.

  1. mb1280

    mb1280

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    How can you tell how good or average a GPS is (cell phone vs dedicated)? Such as:

    an iPhone X, or BLU G90 - - - with no SIM card - - - using MAPS.ME . . . vs . . . a Garmin Drive 51 LM

    Are they all pretty much the same, or are there some specs to consider?

    These pages don't give you anything to go by.

    This would just be for getting around town by car.

    - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - -

    iPhone X - Technical Specifications . . . Assisted GPS, GLONASS, Galileo, and QZSS . . .
    Code:
    https://support.apple.com/kb/sp770?locale=en_US
    BLU G90 - Full phone specifications . . . Yes, with A-GPS . . .
    Code:
    https://www.gsmarena.com/blu_g90-10313.php
    MAPS.ME: Offline Maps, GPS Nav on the App Store . . .
    Code:
    https://apps.apple.com/us/app/maps-me-offline-map-with-navigation-directions/id510623322
    vs.

    Garmin Drive 51 LM | Car GPS - Specs . . .
    Code:
    https://buy.garmin.com/en-US/US/p/552041#specs
     
    mb1280, Feb 12, 2021
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  2. mb1280

    Nuvi-Nebie Moderator

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    You don't say in your post what you want to compare, is it GPS location accuracy or map accuracy?

    MAP ACCURACY

    There are only a few maps companies that supply all GPS makers, I don't think any one supplier stands out more than the otgers

    Garmin maps are supplied by HERE
    MapsMe maps and quite a few other Apps. use Open Street Maps
    Apple use their own maps on their products

    GPS ACCURACY

    There are several factors that affect the postion accuracy

    1. A-GPS where the GPS is Assisted (Augmented) by external data (from the internet)
    2. GNSS satellites in addition to GPS such as Glonass, Galileo, Beidou
    3. SBAS satellites e.g. WAAS, Egonos, MSAS, Gagan, SNAS, SDCM, WADGPS
    4. Dual Band / Frequencies from each satellite e.g. L1 + L2 +L5
    You will find all four of these on both handheld GPSs and smartphones, no 4 is likely to make the biggest jump in accuracy
     
    Last edited: Feb 12, 2021
    Nuvi-Nebie, Feb 12, 2021
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  3. mb1280

    mb1280

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    I was wondering . . . the 3 devices above, relative to each other, how do they compare

    I found this app for the BLU G90, it shows yellow or green for me, for more than 3 satellites, so that indicates to me that it's good:

    GPS Test - Apps on Google Play . . .
    Code:
     https://play.google.com/store/apps/details?id=com.chartcross.gpstest&hl=en_US&gl=US
     
    mb1280, Feb 12, 2021
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  4. mb1280

    Nuvi-Nebie Moderator

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    Although you didn't answer my question in post #2, I'm guessing you want to compare GPS position accuracy rather than map accuracy, I have added some more details on both in my post #2 above

    The short answer to your original question is that all 3 are pretty much the same as far as positional accuracy is concerned
     
    Nuvi-Nebie, Feb 12, 2021
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  5. mb1280

    mb1280

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    Hi! Thanks for the info.

    From these pages, I see that the signal will be good, unless it's blocked by a building, tunnel, or clouds, etc:

    GPS.gov: GPS Accuracy . . .
    Code:
     https://www.gps.gov/systems/gps/performance/accuracy/
    GPS.gov: GPS Modernization . . .
    Code:
    https://www.gps.gov/systems/gps/modernization/
    GPS.gov: Augmentation Systems . . .
    Code:
    https://www.gps.gov/systems/augmentations/
    I see that Google Maps uses Open Street Maps, so that should be good.

    Which gets me to focus on a couple of things with the devices:

    A.) Are there any hardware specs to look at, that determine quality?

    B.) From the GPS Test App, I see that there are different kinds of satellites up there:
    1.) GPS
    2.) GLONASS
    3.) GALILEO
    4.) BEIDOU
    5.) QZSS
    6.) SBAS
    7.) UNKNOWN

    iPhone X specs show that it uses: Assisted GPS, GLONASS, Galileo, and QZSS
    I don't see any info like this for the BLU G90 or Garmin Drive 51 LM.
    I suppose that different devices use different kinds of the above satellites.

    With the GPS Test App, if I select to just see GPS, my BLU G90 says there are 11 "In View", 9 "In Use"
    AVG is 28.4, in the yellow section - very close to green, which is good
    . . . to do GPS, you only need 3 . . . so if 9 are available, then I should have no issues . . . ?

    . . . does 9 "In Use" mean that my BLU G90 is using them? probably not, because:
    . . . if I click to see all of the different kinds of satellites, it says 35 "In View", 27 "In Use"
    . . . my BLU G90 is probably not using all 27 of them
    . . . does this mean that 8 satellites are offline?
     
    mb1280, Feb 13, 2021
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  6. mb1280

    Nuvi-Nebie Moderator

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    Most GPS manufacturers don't reveal which GPS ' chip' they use so you can't compare hardware

    Both the G90 and the Drive51 probably only use B1 (GPS) in your post above whereas the iphone uses B1 to B3, (B5 QZSS only works in Japan) so the iphone is probably a little more accurate

    'In View' means that some data has been received from it but it is not used to calculate position

    'In Use' means it is used to calculate position

    9 and 11 referes th GPS only

    27 and 35 refers to all satellites (including GPS)
     
    Nuvi-Nebie, Feb 13, 2021
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  7. mb1280

    mb1280

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    If the device doesn't specify other kinds of satellites, then, assume it just uses GPS?
    And where I am, there are more than 3 GPS satellites around, so I would have good coverage in this area?

    iPhone X - Technical Specifications . . . Assisted GPS, GLONASS, Galileo, and QZSS . .
    Code:
    https://support.apple.com/kb/sp770?locale=en_US
    . . . GPS (USA) [iPhoneX GPS is "Assisted"? I wonder how. By cell towers?] . . . GLONASS (Russia) . . . Galileo (EU) . . . QZSS (Japan)
    . . . Do the iPhone specifications mean that in addition to GPS (USA), that it uses Russian, European, and Japanese satellites, to help me navigate around the State of Ohio (USA)?
    . . . Or, are they only used, if you're in those countries?
    . . . I don't see any QZSS, so probably yes. Are those geo-stationary satellites above Japan?

    How do cell towers fit in? I've heard that they provide more accuracy, so that's another reason to have a cell phone plan.
    . . . I'm thinking I can do without a cell phone plan, though, and just use offline maps - and WiFi at some big box, if I need to make or receive a call
    Would cell towers be part of the GPS Modernization or Augmentation? (links above)
    If you have more than 3 GPS satellites available to you, do cell towers really provide that much more accuracy?

    Any idea of what's the best app that shows you the number of satellites for iOS?
    I would not be aware of how you can know all this, unless I got this Android OS phone, and the GPS Test App (I see that the GPS Test app I found is different from the one you mention).

    All this is making my head spin. Wow! Really cool! Fascinating
     
    mb1280, Feb 13, 2021
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  8. mb1280

    Nuvi-Nebie Moderator

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    This had already been answered in my post #2
    GPS owned by USA
    Glonass owned by Russia
    Galileo owned by Europe
    Beidou owned by China

    The above have 24 + satellites each that cover the whole world, e.g.they can all be used in every part of the earth
    QZSS owned by Japan only covers (and works in) Japan, not the rest of the earth

    They don't, a smartphone may be able find a rough location using cell phone towers but this is completely separate to GPS navigation they are not connected

    You don't need a cellphone plan (or a cellphone signal) to use the GPS in your cellphone, the GPS gets it's data from satellites not cellphone towers

    I don't have an iphone but here is an App. I found :-
    https://apps.apple.com/us/app/gps-status-toolbox/id1198499960
     
    Nuvi-Nebie, Feb 13, 2021
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  9. mb1280

    mb1280

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    Thanks! This helps me a lot!
     
    mb1280, Feb 13, 2021
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