1

I have learned somewhere that the value returned by the "altitude" property of CoreLocation contains the geoid difference in the calculation.

However, I could not find a description in Apple's official document that shows its basis:
https://developer.apple.com/documentation/corelocation/cllocation/1423820-altitude

Is the description of geoid in altitude of CoreLocation not written in the official document?

Additional Question: Does altitude including Geoid apply to any location all over the world?

Yuma OSHIO
  • 11
  • 2
  • Are you looking for [`CMAltimeter`](https://developer.apple.com/documentation/coremotion/cmaltimeter)? – Pang Jan 24 '18 at 07:34
  • Yes, that means yours. – Yuma OSHIO Jan 24 '18 at 07:35
  • Will this help? [WGS84 Geoid Height Altitude Offset for external GPS data on IOS](https://stackoverflow.com/q/22196714) – Pang Jan 24 '18 at 07:36
  • @Pang It is about the handling of Geoid when using external GPS data. I would like to know about the value measured directly by CoreLocation. – Yuma OSHIO Jan 24 '18 at 07:39
  • It is not about CMAltimeter but about the altitude property of CoreLocation. https://developer.apple.com/documentation/corelocation/cllocation/1423820-altitude – Yuma OSHIO Jan 24 '18 at 07:40
  • Seems not mentioned anyway in Apple's docs: https://encrypted.google.com/search?hl=en&q=site%3Adeveloper.apple.com%20geoid – Pang Jan 24 '18 at 07:44

2 Answers2

1

I can't provide a reference link from Apple since I never found one. But I can say from testing that early iPhone models did NOT correct for geoid, while all models since the iPhone 4 ans all iPad models DO correct for geoid. And yes, AFAIK, the correction is valid worldwide.

Max_B
  • 887
  • 7
  • 16
0

This is a fantastic question and one that I wish had a solid answer, I have seen a few posts that seem to indicate that iOS is using EGM96 or a similar global geoid model as the reference geoid but this has has no official documentation from Apple as far as I can tell.

The following post in the Apple Developer Forums seems to back this up https://forums.developer.apple.com/thread/95874.

This is information that Apple really needs to make available in some way.

Charles Bisbee
  • 103
  • 1
  • 7