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

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

 

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

 

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?

 

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

 

Thanks! This helps me a lot!