[R-390] Magnetic compass and true north

[barry williams]

The military also uses grid north. In the low tech aircraft we navigated 
by military topographical 1:50,000 maps mostly set up on a grid north 
basis. There are 3 norths. Grid north. Magnetic north. True north. We 
also used distance scales of miles, kilometers (the metric system) , and 
statute miles. Three airspeeds- indicated airspeed (IAS), true air 
speed, and ground speed.  Two barometer scales for altimeters- millibars 
and inches of mercury. In Europe around the Brits we used 2 altimeter 
settings, QNH and QNE. We used two terms for switching ATC services- 
everybody used handoffs when being handed off to another ATC service, 
but you had to say hand over around Brits because handoff means a dirty 
act to them.   8^)


the other Barry


> yes sir but pilots navigate to magnetic north always. boats---for some
> reason---are different. they use true north. Don't know why. Maybe avoids a
> conversion from celestial sightings when they used that--R
>
> Roger Gibboni
> Chief Operating Officer
> Dulye&  Co
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>
> On Tue, Sep 9, 2014 at 9:33 AM, Sheldon Daitch<SDAITCH at bbg.gov>  wrote:
>
>> Roger,
>>
>> The wet compass points magnetic north/south, not true north.  But you'd
>> know true north from the magnetic declination charted information.
>>
>> 73
>> Sheldon
>>
>>
>>
>> -----Original Message-----
>> From: R-390 [mailto:r-390-bounces at mailman.qth.net] On Behalf Of Roger
>> Gibboni
>> Sent: Tuesday, September 09, 2014 4:01 PM
>> To: Blair Batty
>> Cc: R-390 at mailman.qth.net
>> Subject: Re: [R-390] OT: Submarine navigation
>>
>> Directional gyro that was reset with star sightings when they could
>> surface.  The longer between star or sun shots the more th DG drifted.
>> Same as in an airplane.  Enen today the only true north pointing instrument
>> in an airplane is the wet compass.
>>
>> Roger Gibboni
>> 845-987-7744
>>
>>> On Sep 9, 2014, at 8:40, Blair Batty<blairbatty at gmail.com>  wrote:
>>>
>>> Sorry for the off topic, but I know there are lots of ex-military
>>> types here; I don't know where else to ask.
>>>
>>> How did a submarine navigate during WW2? Did a compass work underwater
>>> inside an iron tube? Did they just look thru the periscope to see
>>> where they were going? Dead reckoning? Or were they mostly a surface
>> vessel.
>>> I suppose today they have all sorts of magic, electronic gps devices,
>>> so they can travel for months without every surfacing. But what was
>>> available, say in the 60's-70's?
>>>
>>> Sincerely
>>> /b
>>>
>>> Questions inspired by a cold war submarine movie last night...
>>>