Hey guys,
Will like to check with you if anyone have done or have knowledge to do compass pad survey.
Which magnetometer do you use for such work? Scalar or Vector?
What do you use to define accurately the centre of magnetic north?
Also what other information do they need other than the magnetic north and the cardinal points and the declination to true north and position of the centre of the pad.
FAA has information regarding a compass rose in appendix 6 of AC 13-a. For airport purposes I have use the world magnetic model for the declination. This is a compass rose and the lines are painted 6" thick, so keep the accuracies relative to the work.
https://www.faa.gov/documentLibrary/media/Advisory_Circular/150-5300-13A-chg1-interactive-201612.pdf
https://www.ngdc.noaa.gov/geomag-web/#igrfwmm
There's a lot of info and discussion out there if you do a search for: compass pad survey
Some more links that might give a feel for it besides wading through the FAA spec
http://www.iaga-aiga.org/data/uploads/pdf/guides/iaga-guide_compass_base_manual.pdf
http://compass-rose-surveying.com/specifications.html
http://compass-rose-surveying.com/documents.html
I see reference to 1 arc minute accuracy, and "average declination of the site". That's tough to do, and says the magnetic declination model probably won't be accurate enough for a given location. Note that magnetic declination can vary daily and seasonally by more than a minute, and will drift much more within months in some locations.
For true north, a Polaris sight can very easily achieve better than an arc minute. Or base-rover GPS measurements with a little averaging over a sight line of several hundred meters.
Thanks guys! I managed to find loads of information for the US but nothing much in my side of the world.
But could not find much about how to get it done. Thanks will read them up