I too have Theodolite (it was one of the first apps I purchased) and I can also
say that it is a great app!
-Paul, W2PIR
On Dec 23, 2014, at 12:51 PM, Jim Lux <jimlux@earthlink.net> wrote:
> 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 ??/
>>
>
>
> Magnetic sensor in the phone, magnetic variation (difference between true and
> mag) is from table lookup based on known location (e.g. from GPS or WiFi or
> cell system)
>
> Probably good to a few degrees, unless you're standing next to something that
> perturbs the field (bar magnet, big lump o' steel, etc).
>
> It also does detect (in a limited way) whether there is something perturbing
> the field. I think it does it by matching compass reading changes against
> rotation rates from the internal gyros. If the amount of change due to gyro
> doesn't match the amount of change from mag sensor, it tells you that it's
> unreliable.
>
>
> BTW, there's a very nice app called Theodolite for the iPhone (not for
> Android yet). Very useful: it has angle displays and calibrated stadia marks
> so you can tell if your tower is vertical, etc.
>
>
>
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