> You probably already know this; but, just in case I feel compelled to say something.
>
> Establishing "Magnetic North" is much more complex than just going out and holding up a hand compass. To do the job properly it takes many readings from several locations (all tied together of course).
>
> From what you describe it sounds like whoever wrote the description of the work needed had no clue what they really need and meant.
>
> Larry P
This is exactly the case. Some architect threw it in the requirements for a site topo of maybe 2 acres. I guarantee they don't know why they requested it. You know they're not going to orient their apartment building to anything but the property lines, so magnetic north is just a waste of time. I'd love to ask them what they plan on doing with the magnetic declination adjustment.
don't overcomplicate things
In my area, we simply take a few compass bearings at different points along the traverse loop, throw out the high and low and average the rest and base the plan and deeds on magnetic north observed on that day.
If they want a true north arrow, we draw one 15.5 deg. to the right of the Magnetic North arrow. (Your declination may vary).
Of course, virtually all deeds and plans in my area are magnetic so very few people actually care where the axis of rotation of the earth is to the nearrst ARC second.
I have a feeling this problem is being way over analyzed.
Probably someone who didn't know anything about surveying needed to write a spec for surveying services and they knew USGS quadrangle maps have the magnetic declination on them (mostly they are off by several degrees in California) so it must be something they want.
In one of my previous jobs I was occasionally asked to review these specs and I was always amazed at the crazy stuff they put in there. I rewrote them to be more in line with how real Surveyors actually do things.
Do you think its for solar panels on top of a proposed building?
Installation of solar panels is one of the two times "North" was critical.
Solar panels "critical" to a very broad range. One degree should be great. And far better to set stakes for aiming than to use a compass on top of a building that may have steel in it.
Okay, so I hear what you're saying. You need to show the difference between True and mag. Easy enough. Set your control with your Trimble GPS (that's the here position) using WGS84 LLH. Calibrate to one point using 5k,5k. It reduces it to a plane and if your job isn't too big, this will work.
Then, when you're done, take a compass observation with a hand compass on a line you know the direction of and show the difference in the North Arrow. Loyal is dead on accurate when he says it's a moving target. Don't let it hurt your head. Odds are it's some old stupid checklist thingy and you need to comply. I've had to do it and I've NEVER had a problem with the above.
If you're a little aprehensive about it, I put a note stating that the difference between mag and true is 03° based on a bruton pocket transit with 0° set in the declination observed on some day.
If you can't dazzle them with brilliance, baffle them with bullstuff.
All Please keep in mind..
its 2012, and if the Mayans are correct, magnetic north should changes significantly this year.:-)
I use magnetic north on every survey I do.
I use a compass to get magnetic north on site. You can average it with several observations throughout the survey. I check it at every traverse to look for local disturbances.
From what it sounds like you could get an average from the website magnetic declination or do an observation.
I used magnetic north in the airplane but the compass only reads to the nearest 5°.
Runway numbers are based on the magnetic heading of the runway to the nearest 10°.
Here north south runways are almost always 16-34.