Does iPhone/iPad use GPS and GLONASS in the same time? Can I manage them?

Question

I know that iPhone/iPad could use GPS and GLONASS, but does they use they in the same time?

I didn't find that info in documentation. GPS demand 4 satellites for proper work, (3 without altitude). Same thing with GLONASS. So, if we use just GPS we get 4 satellites and get's our standard GPS accuracy, and it's tolerance about 10-20 meters in open sky. I didn't find specified accuracy on wiki GPS page, maybe I just missed, but anyway my numbers is close. As said wikipedia, GLONASS accuracy for civilian usage is very slightly less accurate than GPS, but on high latitudes (north or south), GLONASS' accuracy is better than that of GPS due to the orbital position of the satellites. GLONASS

So, if we use both systems simultaneously, we have a great accuracy improvement because we have 8+ satellites from both systems. My question is: does iPhone/iPad use both systems and their location coordinates still sometimes very inaccurate? Is there a way to turn on/off one of the systems?

Answer 1

iOS locates the current location with all available services. That means GPS, mobile telephony transmitters (mobile cells), WLAN, and the newer iPhone with GLONASS. We have no way to decide programmatically which system exactly we want to use, but there are different ways to use the iOS location services. The desired accuracy and other parameters can be set via the CoreLocation Framework classes.

You should read the Location Awareness Programming Guide from Apple.

Answer 2

The main advantage of using GLONASS together with GPS is in situations with bad view to the sky, e.g., in urban canyons.

In that case, the additional GLONASS satellites may help.
In open sky situations, a combined GPS/GLONASS has no accuracy benefit to a GPS chip alone.

You cannot switch off any one of the GNSS systems in iOS. (iPhone 4S is the first iPhone that uses combined GPS/GLONASS).