15
   

The Earths Magnetic Poles will reverse .

 
 
roger
 
  1  
Reply Sun 16 Jan, 2011 02:45 pm
@georgeob1,
To the nearest 10 degrees!? We used to use the compass rose to swing the compass. No wonder Army pilots kept coming back an saying 'We just can't get there from here".
0 Replies
 
farmerman
 
  1  
Reply Sun 16 Jan, 2011 03:30 pm
@georgeob1,
Agonic line shifts are most affected the closer to the poles, howqever, when airports like Florida need to renumber their runways, thats some moving.
Most new gps systems are "Agonic free" swince they use geodesy rather than earth reference points that need to be corrected all the time.
Only trouble is that , in Pa, my ref calibration for surveying and alidades is about 0.2 degrees per year , Used to be 0.11.
EDM surveying equipt is all hooked up to the web and does the corrections in real time cause surveyors (usually engineers) are the biggest **** ups.
georgeob1
 
  1  
Reply Sun 16 Jan, 2011 05:23 pm
@farmerman,
Lots of variation in the use of terms here. Local "variation" is the difference between the direction of true north (earth's axis) and the magnetic north pole. "Deviation" is the difference between the direction of the magnetic pole and the reading on a particular magnetic compass in a particular installation. "Can Dead Men Vote Twice: was the memonioc for recalling the sequence of corrections from compass readings to true bearing.

"Declination" , as I know it is an astronomical term referring to the vertical coordinate of a star's position relative to the equator on a given day. It appears that it is also used to denote the local magnetic variation, absent any local effects (which in many areas of the world are larger than the differences between the magnetic and rottational poles. Is this correct? (A question for farmerman, who, as an overbearing geologist, should know.)
farmerman
 
  1  
Reply Sun 16 Jan, 2011 06:21 pm
@georgeob1,
Well, I think that engineers spend more time recording these mnemonics when all ya gotta know is that the magnetic elements are 7. You only need know them once in your life , the rest of the time, its on yer field notebook or I-pad as an empty table.
Lessee if I can recall em all
Declination, inclination, sigma intensity, xintensity, zintensity,North Component and East Component. When we determine mag inclination we must determine the x and z intensity.
You use "variation" and that defines you as a pilot or engineer. We need to know our position in dimensions beneath the earth as well

Quote:
farmerman, who, as an overbearing geologist, should know.)
now, you have defined a "Soil scientist or geotechy engineer" I only deal with "Underbearing" or underburden.
Declination is a treat for juggies and beginning field members. In order to define the "North of the celestial meridian", we set up a transit station on Polaris and watch the columation of three stars (Polaris, delta and mizar)as they define a vertical line wrt our optical plummet. This occurs twicw a day and we need two columations for a map position to coordinate "true north"with our GPS readings. That means that some kid is gonna stay awake for a long time. Then they will need to QA their own readings.

Its good to be the boss.
BUT, magnetic reversals will probably not mess up our direction finding unless some wag detonates a big one and we get an EMP to shut down our gadgest
georgeob1
 
  1  
Reply Sun 16 Jan, 2011 06:30 pm
@farmerman,
Ah ! So in the geologist's vernacular "declination" is what a saner pilot., mariner, or engineer would call "variation". I suspected as much. N0 self-respecting engineer would accept the requirement for 7 distinct coordinates to determine the orientation of field lines in a three dimensional space - I infer that 3 of the seven are redundant relative measures, but what is the extra one for?

When I was with Dames & Moore there was continuous warfare between the soil engineers and the geologists. "There's one under every rock" was the way the engineers referred to the geologists (or was it the way the geologists referred to the engineers?).
farmerman
 
  1  
Reply Sun 16 Jan, 2011 06:54 pm
@georgeob1,
Quote:
I infer that 3 of the seven are redundant relative measures, but what is the extra one for?

we have to break up mag fields into x/y/z components so that we can increase our boundary accuracies to sub centimeter levels.You know that, in terms of claims, a few inches can mean litigation.

0 Replies
 
Setanta
 
  1  
Reply Mon 17 Jan, 2011 04:15 am
This thread has gotten boring . . . is the sky falling yet?
farmerman
 
  1  
Reply Mon 17 Jan, 2011 04:25 am
@Setanta,
Only in Boston , Seattle and Baltimore
0 Replies
 
edgarblythe
 
  1  
Reply Mon 17 Jan, 2011 05:28 am
I saw a story the other day, in which the author voiced an opinion that the magnetic pole change causes all those birds to die. Didn't bother to read much beyond the headline.
farmerman
 
  1  
Reply Mon 17 Jan, 2011 07:26 am
@edgarblythe,
We can blme a lot of things on polar reversals, even if theyre not true. I blame polar reversal for giving us Sarah PAlin and "Dancing with the STars"
Ragman
 
  1  
Reply Mon 17 Jan, 2011 10:05 am
@farmerman,
Thread diversion alert:
Yeah..well for some of us the poles DID reverse yesterday with the Jets beating Pats. Wahhhh!

Sorry, back to control of your thread viewing pleasure.
0 Replies
 
Walter Hinteler
 
  1  
Reply Mon 17 Jan, 2011 10:24 am
@georgeob1,
georgeob1 wrote:
"Can Dead Men Vote Twice: was the memonioc for recalling the sequence of corrections from compass readings to true bearing.


CDMVT AE = 'Can Dead Men Vote Twice At Elections' (add east) .... you certainly do know that, too (from hear-say ... the work was done by odd-job men ... like me Wink)
georgeob1
 
  1  
Reply Mon 17 Jan, 2011 08:46 pm
@Walter Hinteler,
Does it work in German??
0 Replies
 
High Seas
 
  1  
Reply Thu 27 Jan, 2011 05:57 am
@farmerman,
farmerman wrote:
...BUT, magnetic reversals will probably not mess up our direction finding unless some wag detonates a big one and we get an EMP to shut down our gadgest

Wouldn't you want to keep satellite-based backups for your star-based coordinates? Or do you worry they too would vanish with a solar flare?
farmerman
 
  1  
Reply Thu 27 Jan, 2011 06:53 am
@High Seas,
we only need about 4 satellites for a decent position at meter levels of accuracy. We keep (usually) more than 28 to 30 satellites on any given plane of reference . SO while we may lose sub centimeter accuracy, we can always keep optical and laser distance measuring "for government work" and just have a decent duplicate mass of satts up there still woprking. All that can change is we get a series of "ewdge over" type flares .
AS far as an EMP, Im afraid we would be totally screwed and would have to rely on buried land lines and cable tv for a long while.
High Seas
 
  1  
Reply Thu 27 Jan, 2011 07:26 am
@farmerman,
28 to 30 satellites works above approx. N30 and not in all E-W longitudes - but then elsewhere neither would the stars you mention anyway.

Only asked because EMP not likely except in specific locations for a number of reasons. But if - iff, and you know that's no typo - you're prospecting for rare earths you know that regardless of the Unocal Chinese bid - wildly bruited about as a petroleum bid, when it was about a rare earths mine - there are very few places above N30 where EMP might be a concern. I just don't know why you would worry about EMP anyway since all your instruments are land-based, so easy to shield without loss of mobility. Satellite- and aircraft-borne instruments are so much harder to shield, given the added weight. Gold works miracles as a shield, wonder why lead (with more empty spaces in the outer electron orbits) is used instead - unless it's price.
farmerman
 
  1  
Reply Thu 27 Jan, 2011 08:06 am
@High Seas,
All geophysical instruments are now Sat connected. Its easy to integrate circuits with satt nav tech and (because GPS is so cheaply done at the accurcies needed for stuff like seismic and magnetometrics, we dont even carry plane tables and crap along anymore.

Why the curious admixture of concern for "rare earth" el;ements? These arent really a problem. This is my field entirely Just cause the Chinese want to suck up many, we still hve the largest deposits of monazite sands and pegmatites along with Western Europe. Newspapers arent that infoprmed about raw materials. Its too boring a subject for mass digestion. A Chinese "plot to take over our precious bodily fluids" makes a lot better readership

Africa is a big continent but its not as geologically active as us and Wurope.
farmerman
 
  1  
Reply Thu 27 Jan, 2011 08:08 am
@High Seas,
Quote:
but then elsewhere neither would the stars you mention anyway.

Delta Mizar and Polaris are a "bench mark" they work all over the N. hemisphere (except at the really low latitudes where we have to use only 2 stars or an imaginary "X" plane.
0 Replies
 
High Seas
 
  1  
Reply Thu 27 Jan, 2011 08:14 am
@farmerman,
Thanks - mineral resources and China have been a big issue as you know for US/Canada, Australia, Russia, and even some Africans. I wasn't particularly concerned about their scarcity, but prices have been rising as you know for all "rare" minerals so it's a valid concern, financially speaking.

You know I know 00.00 about geology, so even though this isn't on topic I'd like to ask: is the Yellowstone giant volcano's latest bulge a cause of concern? Not that it might go ka-boom (yes, hardly a sophisticated geological term!), but in the sense it deforms the geoid enough to change magnetic lines?
farmerman
 
  1  
Reply Thu 27 Jan, 2011 08:32 am
@High Seas,
the changes from any seismic bulge are minimal and transient features. Now if Yellowstone were to erupt in the way it did last time, we would be in big trouble as a nation. Worldwide weather would be affected but our entire midwest and plains would be pretty much covered with thick breccias and ash.
Therev been several scenario discussions at high enough circles and the contingencies involve some alternatives that arent very nice.
 

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