Need help finding true south

[RugbyRene]

Hi all,

I need the help of the brains trust.

I'm in the process of installing a pier. I got a concrete base poured and of course used galvanised rebar to reinforce it. Now I'm at the point of aligning the pier to true south but am concerned the rebar in the concrete base will affect any compass I use and give me a false reading.

So, I'm looking for a creative solution on how I can still use a compass to find true south and align my pier.

Cheers

Rene

[Drac0]

A well aligned stick in the ground at solar noon works well. Seriously, and winter is the better time to do it, getting a longer shadow.
https://www.iceinspace.com.au/forum/showthread.php?t=201525

Cheers,
Mark

[RugbyRene]

Thanks for that. It's always the simplest and oldest ways of doing things that are the best.

Rene

[Shawn]

I built mine to adjustable, with oval radial bolt down points that allowed a small amount of rotational adjustment via jacking screws, to compensate for any settling of the pier or slab at a later point, I also insulated the per from the surrounding concrete slab with foam strips to eliminated vibration transfer of walking around etc. Oh, the picture is still here...https://www.iceinspace.com.au/forum/attachment.php?attachmentid=23055&d=1170320323
Its an old picture of the pier made for my lat in the process of fabrication, but if its not too late, the image maybe useful.

[Merlin66]

Rene,
There's a very good free software app that does it for you:
https://www.suncalc.org/#/-36.7798,144.3429,17/2023.01.19/14:57/1/3


Just enter your location and it will show you the time of solar noon transit and the length of shadow.
Very accurate and easy to use.

[RugbyRene]

Thanks for that. Seems like a very good site. Just need to build my dowel contraption.

Rene

[RugbyRene]

No, I'm buying mine readymade and there's no play in the bolt holes. No worries though. I should be able to figure it out with my dowel system.

Rene

[RugbyRene]

Well, I think I may have solved my dowel problem. I had a look around the house and found that I had a tamper, which seems perfect for the job. It has a nice long pole, and flat, stable base. The only minor issue I can see is the handle is a bit wider than required ( probably 2cm wide) which will give me a wide shadow, but if I draw the north south line along one of the edges of the shadow cast by the pole then I should be good.

Anyone else see any issue?

Rene

[PaulSthcoast]

Hi Rene

I just use a plumb bob on a piece of string.

Let gravity do the work.

Gives a nice straight line to follow.

If you don't have one...then just a simple weight
on the end of some solid twine works too.

Then I use another piece of twine to peg out
the shadow along the ground.

If it's on concrete...draw it in.

There's the south line.

Hope it might help.

Paul.

[RugbyRene]

Thanks Paul. I'll have a look at that if my tamper idea doesn't work but to be honest, I don't see why it wouldn't. I've already tested it and the shadow it casts will also give a nice straight line that I can draw on my base.

Rene