I made a simple app which displays the altitude according to the GPS position on iPhone. How is the altitude obtained? Does it get the altitude of the land at the coordinates I am or does it get the actual altitude? (I tried the same application in the same building; once at ground floor and once on the third floor but the same altitude is displayed) Is it possible to obtain a different altitude on different floors? (Like my android phone has a barometer sensor and I calculate the elevation by the atmospheric pressure; but none of the iPhones has a barometer sensor)

iphonegpsaltitude

duncanportelli

Reputation: 3229

How does my iPhone get its altitude?

I made a simple app which displays the altitude according to the GPS position on iPhone.

How is the altitude obtained?
Does it get the altitude of the land at the coordinates I am or does it get the actual altitude? (I tried the same application in the same building; once at ground floor and once on the third floor but the same altitude is displayed)
Is it possible to obtain a different altitude on different floors? (Like my android phone has a barometer sensor and I calculate the elevation by the atmospheric pressure; but none of the iPhones has a barometer sensor)

Upvotes: 6

Answers (5)

user23642164

Reputation: 1

According to Apple’s support feedback I got few years ago, iPhone gps sensor only measures longitude and latitude but not altitude. Altitude data is taken from map landscape database instead. That why iPhone shows same altitude at any floor or even on rooftop of the building.

Upvotes: 0

rism

Reputation: 12132

Note that newer IPhones (>= 6) have a barometer sensor which in my experience is significantly more accurate than GPS. With a barometers the accuracy appears to be within a foot whereas with GPS it would bounce around by 3-4 meters even when standing still.

http://www.iphonetricks.org/iphone-6-barometer-sensor-features/

Upvotes: 0

SPA

Reputation: 1289

The altitude as read by the gps receiver depends on the positions of the satellites over the horizon, relative to each other. It is possible then for the altitude reading to be unreliable when either there are not enough satellites in the sky or they are too close together. This then depends on the time of day, or date.

The signals from the satellites are very weak once they have reached the Earth's surface, and may not be received correctly inside buildings, or where there are other tall buildings nearby, such as a city centre like Manhattan.

Barometer readings will vary according to the weather and so an absolute reading can't be applied to a specific floor. However relative readings may be reliable enough for floor to floor changes, e.g. a lower value means going up.

Upvotes: 5

LucaSpeedStack

Reputation: 501

Your smartphone uses GPS technology to calculate your altitude depending on where you are. It measures how far away you are from the satilites which is calculating this information.

Upvotes: 1

Michael Dautermann

Reputation: 89509

Like any other device that uses GPS to calculate altitude, it's measuring the user's distance from the center of the satellites' orbits.

Upvotes: 1

How does my iPhone get its altitude?

Answers (5)

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