Magnetic variation

Submitted: Saturday, May 17, 2008 at 10:37
ThreadID: 57693 Views:9789 Replies:6 FollowUps:11
This Thread has been Archived
I'm sure you sailors out there will know the answer :)

I'm trying to discover the current magnetic variation for Melbourne (accuracy to 0.5 deg will do) and am somewhat confused: if I'm reading it correctly the Geoscience Australia calculator gives a result of 5.498 deg. but web searches indicate about 11.3 deg?

GSA calculator

Mike Harding
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Reply By: Member - David P (VIC) - Saturday, May 17, 2008 at 11:00

Saturday, May 17, 2008 at 11:00
1s 1.3 sounds spot on.....cheers ...silverback
AnswerID: 304301

Follow Up By: Member - David P (VIC) - Saturday, May 17, 2008 at 11:01

Saturday, May 17, 2008 at 11:01
oops 11.3
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Reply By: Member - Roscoe ET (QLD) - Saturday, May 17, 2008 at 11:28

Saturday, May 17, 2008 at 11:28
Mike,
Mike I can't get the calculator to work for your area keeps coming up with a blank page. I have checked the calculator against the charts I have for where I fish (Hervey Bay) and it is spot on, a variation of 10.319 degrees E same as the chart.

11.3 degrees E for where you are should be accurate it couldn't be 5.498 degrees.

I went into Google earth and with the pointer over Melbourne I came up with Lat37.44 75E and Long144.55.39S. When you performed the calculation did you make sure you had a - in front of the Latitude figure it needs to be a - because we are south of the Equator and + for Long because we are east of Greenwich.
AnswerID: 304305

Follow Up By: Member - Roscoe ET (QLD) - Saturday, May 17, 2008 at 11:42

Saturday, May 17, 2008 at 11:42
Mike,

I meant to add, get a look at a chart of Port Phillip Bay it will have the variation in the compass rose on the chart.
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Reply By: Member - Nev (TAS) - Saturday, May 17, 2008 at 11:30

Saturday, May 17, 2008 at 11:30
Hi Mike,
Possibly another site to check your figures

http://www.pangolin.co.nz/almanac/magvar.php

Rgds
AnswerID: 304306

Reply By: aussieguy77 - Saturday, May 17, 2008 at 11:31

Saturday, May 17, 2008 at 11:31
Deffinatly not 5.
I think 11.3 may be correct. Brisbane is 11.
AnswerID: 304307

Reply By: Member - Reg T (WA) - Saturday, May 17, 2008 at 11:41

Saturday, May 17, 2008 at 11:41
11.5 deg East Through Melbourne Airport and about 11.6 deg East through Melbourne City.
Information obtained from Melbourne WAC Chart
AnswerID: 304311

Follow Up By: Member - Roscoe ET (QLD) - Saturday, May 17, 2008 at 11:49

Saturday, May 17, 2008 at 11:49
I love your rig Reg that would have to be a real adventure doing it that way, good on you!!
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Follow Up By: Member - Reg T (WA) - Sunday, May 18, 2008 at 09:43

Sunday, May 18, 2008 at 09:43
Have you checked out my camper in my Profile.
I think it shows you dont need much to have a great time in our Australian outback.
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Follow Up By: Member - Roscoe ET (QLD) - Sunday, May 18, 2008 at 12:07

Sunday, May 18, 2008 at 12:07
Yes I did notice your camper. Good thing about your rig is you don't have to worry about the best tyre to get, don't have to worry about sidewall punctures or getting bogged!!!
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Reply By: Mike Harding - Saturday, May 17, 2008 at 12:05

Saturday, May 17, 2008 at 12:05
Thanks guys – 11.3 deg will do me.

I found the problem with the calculator; the page is a little misleading in that it has a “Place name location” box at the top and I assumed if I typed a name in there it would use that as a location however it uses the Lat/Long coordinates (default is 24/135) but still prints the name of the place you typed in when it gives results!? Once I put the correct coordinates for Melb in I got the expected result.

FYI. I want the info for the purpose of aligning directional radio antennas.

Thanks again.

Mike Harding
AnswerID: 304313

Follow Up By: Member -Signman - Saturday, May 17, 2008 at 12:44

Saturday, May 17, 2008 at 12:44
I would've thought to align the antenna to 'true' not 'magnetic' ..
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Follow Up By: howie - Saturday, May 17, 2008 at 15:15

Saturday, May 17, 2008 at 15:15
he needs to subtract/add the magnetic deviation.
if a target was 180 from his position on the map, and using a compass to find this heading, the reading would be 11 degrees out because of the magnetic deviation in that area.
your gps can probably be set for true or magnetic.
ozie CE can display the local deviation if reqd, which i find handy.




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Follow Up By: Member -Signman - Saturday, May 17, 2008 at 16:29

Saturday, May 17, 2008 at 16:29
Be careful here howie....Don't want to start an arguement but..
There is a difference between magnetic deviation and variation..


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Follow Up By: Mike Harding - Saturday, May 17, 2008 at 17:34

Saturday, May 17, 2008 at 17:34
Signman:
Judging from your original post I'd say you have been doing an internet search (Wikipedia) and have next to no idea what you're talking about.

Mike Harding
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Follow Up By: howie - Sunday, May 18, 2008 at 10:24

Sunday, May 18, 2008 at 10:24
no worries signman, i do know the difference, it was a slip of the keyboard.
i use an adjustable compass that i calibrate for deviation.
ozieCE incorrectly has "mag dev" as default, which i have changed to "mag var"
and in a small experiment (OK i'm bored) using a small crappy compass, placing it near objects.
computer screen - 40 degrees out
mobile phone - 60 degrees out
bluetooth GPS - an ironic 120 degrees out
be careful with your compasses people.

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Follow Up By: Pajman Pete (SA) - Monday, May 19, 2008 at 17:07

Monday, May 19, 2008 at 17:07
I have fond memories watching a bunch of sailors working out where they were at a track intersection in the Gembrook state forrest with a map and compass.

They had the variation worked out and were orienting the map to north - on the bonnet of a land cruiser. I (the instructor) questioned this but some bright spark told me that it was all OK - the bonnet is aluminium and non-magnetic.

He was so happy with this answer I chose not to enlighten him about the effect a V8 motor just inder the bonnet would have on the deviation (about 90 degrees in this case). We all took off up the wrong track and they got themselves (but not me) seriously lost.

The really hilariious bit was they they had stopped under a sign with both tracks posted! The exercise debrief an hour later was a lot of fun.

Cheers

Pete
Any mug can be uncomfortable out bush

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