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Old 06-01-2014, 23:20   #1
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Naval Heading and Bearing?

In the Navy (or Hollywood movies) when a sonar engineer or navigator mentions a course heading or bearing, is it magnetic or true?
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Old 07-01-2014, 02:47   #2
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Re: Naval Heading and Bearing?

Dunno but in Hollywood it doesn't matter and I am guessing the navy uses true these days as electronic navigation is most often in true...
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Old 07-01-2014, 03:42   #3
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Re: Naval Heading and Bearing?

I recall using true. Magnetic changes and you usually have no time to play out calculations for wherever you are...that is what Quarter Masters are for!
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Old 07-01-2014, 03:49   #4
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Re: Naval Heading and Bearing?

Sonar people use so many degrees either red or green ... nobody in that side of the trade gave/gives a monkey's about anything but relationship to ship's head.

Helm orders from about year dot would have been true as ships had gyros which is what the helmsman would be steering by , a gyro repeater... unless you are talking about USS Coy of NZ which was a very slow adapter...
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Old 07-01-2014, 03:56   #5
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Re: Naval Heading and Bearing?

'Year dot'.... tramp ships and such built during and just after WW2 still only had two magnetic compasses ... steering compass in the wheelhouse... standard compass on the monkey island. Cargo liners and other such posh stuff had a gyro repeater in the wheelhouse but still had the standard (magnetic compass) up top.
I don't know what the cut-off was in the navy , maybe small ships such as corvettes still only had magnetic ... dunno

The gyro repeater would typically get its info from a Sperry Mk 14. They were pretty common when I went to sea... Sperry Gyrocompass Mark 14
I think it sired the Tardis
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Old 07-01-2014, 04:33   #6
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Re: Naval Heading and Bearing?

Oops ...meant to say 'sired the Daleks'
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Old 07-01-2014, 04:55   #7
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Re: Naval Heading and Bearing?

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Sonar people use so many degrees either red or green ... nobody in that side of the trade gave/gives a monkey's about anything but relationship to ship's head.........
Not true anymore. All bearings above or below water are true and related to a WGS84 representation of the world for location.
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Old 07-01-2014, 05:01   #8
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Re: Naval Heading and Bearing?

From my experience in the "Grey Funnel" line everything was pretty much True. However lookouts would report sightings (aircraft/ships etc) as a relative bearing - e.g. Ship bearing green 45 - which would mean 45 degrees on the Starboard bow as they generally did not have access to a pelorus (being the preserve of the officer of the watch) The OOW would then be able to sight the target using the pelorus mounted on a gyro repeater to get the true bearing. The radar people in the CIC would have detected the target a long time before it was seen, but always useful to compare with the MK1 eyeball sighting.

In the signals world, we would prepare signals (ship stationing and manouvering) using true and relative bearings depending on the situation.

A signal to turn ships could be sent as "turn stbd 9" which means ships are to turn together 90 degrees to starboard relative to the course currently being steered. Or could be signalled as "turn stbd 180" with would be turn together to the true course of 180.... 6 of one 1/2 doz of the other..
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Old 07-01-2014, 05:02   #9
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Re: Naval Heading and Bearing?

Refering to post #7
I'm surprised at that... so when the lookout on the port bridge wing reports a light ( and having no idea which way the ship is pointing) he says ' light bearing 235 degrees' and not ' light 2 points to port' ...
My ... how things change...
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Old 07-01-2014, 05:37   #10
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pirate Re: Naval Heading and Bearing?

If memory serves me well.. and its been over 40yrs now.. when I picked up an definite echo I gave a bearing relative to the ships heading.. then guided the skipper in by dancing across the target from left to right and back again when I got a 'dead' transmission.. and the Range Finder would give our closing speed/distance..
I imagine things have moved forward a lot in the Royal since then
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Old 07-01-2014, 05:54   #11
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Re: Naval Heading and Bearing?

Hollywood has its own "speak-ease" for movie goers to understand technical navigational lingo, whether it is naval or for aviation. Common chatter, seen in Hollywood films, is not allowed when communicating with Air Route Traffic Control Centers (ARTCC). Two-way communications are very brief and to the point. Emergency communications involve the usage of 4-digit transponder codes, known to pilots worldwide; you never hear of those codes mentioned in any movie.

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Old 07-01-2014, 06:53   #12
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Re: Naval Heading and Bearing?

Quote:
Originally Posted by El Pinguino View Post
'Year dot'.... tramp ships and such built during and just after WW2 still only had two magnetic compasses ... steering compass in the wheelhouse... standard compass on the monkey island. Cargo liners and other such posh stuff had a gyro repeater in the wheelhouse but still had the standard (magnetic compass) up top.
I don't know what the cut-off was in the navy , maybe small ships such as corvettes still only had magnetic ... dunno

The gyro repeater would typically get its info from a Sperry Mk 14. They were pretty common when I went to sea... Sperry Gyrocompass Mark 14
I think it sired the Tardis
Most late WWII cargo vessels had Sperry Gyro Compasses. The Gyro compass was in the gyro room, deep in the vessel. There were repeaters in the wings of the bridge and in the wheelhouse. Also magnetic compasses in the wheelhouse and up top on the monkey island. On older vessels without wing repeaters you had to go up to the monkey island to take bearings.

The gyro compass was shut down when in port and started usually about 24 hours before putting to sea. The maximum error on the gyro was one or two degrees, not stated as E or W but high or low.

Compass errors were always checked by taking amplitudes. Ah, the good old days when the officer on watch had to do a thing or two.
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Old 07-01-2014, 06:57   #13
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Re: Naval Heading and Bearing?

We always use a true bearing. There are times when the relative is used as a point of reference to an object sighted.
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Old 07-01-2014, 07:32   #14
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Re: Naval Heading and Bearing?

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Common chatter, seen in Hollywood films, is not allowed when communicating with Air Route Traffic Control Centers (ARTCC).Two-way communications are very brief and to the point
various you tube recordings of ATC chatter would seriously suggest otherwise, Not to mention when ( I Think ) American that allowed you to listen to pilots VHF chatter, I remember chatter about hockey scores, stock markets, girlfriends and "the big game"

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Old 07-01-2014, 07:43   #15
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Re: Naval Heading and Bearing?

Quote:
Originally Posted by Vasco View Post
Most late WWII cargo vessels had Sperry Gyro Compasses. The Gyro compass was in the gyro room, deep in the vessel. There were repeaters in the wings of the bridge and in the wheelhouse. Also magnetic compasses in the wheelhouse and up top on the monkey island. On older vessels without wing repeaters you had to go up to the monkey island to take bearings.

The gyro compass was shut down when in port and started usually about 24 hours before putting to sea. The maximum error on the gyro was one or two degrees, not stated as E or W but high or low.

Compass errors were always checked by taking amplitudes. Ah, the good old days when the officer on watch had to do a thing or two.
Yard auxiliary vessels @75 feet were equipped with Gyro and used True bearings.
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