[TowerTalk] Smart Phone Compass

[Jim Lux]

On 12/23/14 12:37 PM, Wayne Kline wrote:
>   OK  I do not want this to morph into the many proven ways to find TRUE north.
>
> The compass extra on a I phone..... True north .... I assume it is via GPS tribulation ??/
>
>

To follow up on the inherent accuracy or not of the iPhone, here's what 
the author of the Theodolite app says:

On the latest iOS devices under optimal conditions (clear line of sight 
to 4 sats), you can see GPS position accuracy as good as 10 feet and GPS 
altitude accuracy as good as 15 feet. Azimuth accuracy can be as good as 
2-5 degrees under optimal conditions (minimal magnetic interference). 
All of these accuracies degrade as conditions degrade.

An exception is gyro/accelerometer accuracy, which is fairly steady at 
0.1 deg under a range of conditions. So, any measurements or 
computations using elevation/horizon angles (such as rangefinging, 
targeting, surveying, observation, etc) can be quite accurate. Optical 
measurements in the app (rangefinder) are also quite accurate, and will 
be as good as the user’s ability to read the screen and interpret results.



Good enough for HF, probably not for moonbounce on UHF