|
View previous topic :: View next topic |
Author |
Message |
plummer150
Joined: 04 Jan 2003 Posts: 542 Location: Jersey City, New Jersey
|
Posted: 12/12/2003, 2:03 pm Post subject: Magnetic Declination |
|
|
|
|
Here is probably the most information site I have seen on the web about Magnetic Declination. A lot of the info on here I didn't even know myself until I read it. Like this:
Quote: |
Most people incorrectly believe that a compass needle points to the north magnetic pole. But since the Earth's field is the effect of complex convection currents in the magma, which must be described as several dipoles, each with a different intensity and orientation, the compass actually points to the sum of the effects of these dipoles at your location. In other words, it aligns itself with the magnetic lines of force. Other factors, of local and solar origin, further complicate the resulting field. It may be all right to say that a compass needle points "magnetic north" but it only roughly points to the north magnetic dip pole. |
Crazy, I always thought it was magnetic north too until I read that. Heres the website. http://www.geocities.com/magnetic_declination/ _________________ "IRONMAN" cometh, hiketh, destroyeth |
|
Back to top |
|
|
CatValet Got Gear?
Joined: 04 Jan 2003 Posts: 735 Location: Scottsdale
|
Posted: 12/12/2003, 4:55 pm Post subject: |
|
|
|
|
It's about 14 degrees east of true north hereabouts. -R |
|
Back to top |
|
|
Nighthiker
Joined: 05 Jan 2003 Posts: 1714
|
Posted: 12/13/2003, 9:33 am Post subject: |
|
|
|
|
I had been aware of this Plummer. I have 700 plus USGS topo quads. Some of my maps the magnetic declination has gone from 12 degrees east to 14 degrees east and back to 11 1/2 degrees east. If you have some USGS topo maps for several different locations across a state, check the declination on them. You may note several degree declination difference. |
|
Back to top |
|
|
Tom Treks Gear Addict
Joined: 12 Jan 2003 Posts: 3347
|
Posted: 12/13/2003, 9:37 am Post subject: |
|
|
|
|
Nighthiker wrote: |
I had been aware of this Plummer. I have 700 plus USGS topo quads. Some of my maps the magnetic declination has gone from 12 degrees east to 14 degrees east and back to 11 1/2 degrees east. If you have some USGS topo maps for several different locations across a state, check the declination on them. You may note several degree declination difference. |
Wow. Are any of those electronic?
I've heard that most of the high-end compasses you can buy in a given location already are set for the average declination. Is this true? |
|
Back to top |
|
|
plummer150
Joined: 04 Jan 2003 Posts: 542 Location: Jersey City, New Jersey
|
Posted: 12/13/2003, 9:52 am Post subject: re: |
|
|
|
|
Wow, I did not realize this at all. I do have several topo maps from different years that I'll have to check that out on. I think the latest update for the State College area is 86 and before that was 74 and I have both so I'll see whats up with that. I heard the USGS is actually going to do the State College area again here soon. I'll believe when I get the new updated topo map myself. _________________ "IRONMAN" cometh, hiketh, destroyeth |
|
Back to top |
|
|
azhiker96
Joined: 05 Jan 2003 Posts: 1419
|
Posted: 12/16/2003, 8:46 am Post subject: |
|
|
|
|
Tom, some of the high end compasses can be set for the local declination. They can't sense it though. If you had one you'd want to learn how to adjust it and then set it with the declination from the map where you're hiking.
However, keep in mind that the magnetic pole is moving about 10 miles a year. It's also declining and will likely switch in a couple thousand years. Maybe it's time for me to invest in one of those dang GPS units everybody loves.
http://www.rense.com/general26/poles.htm |
|
Back to top |
|
|
Hnak
Joined: 06 Jan 2003 Posts: 1766 Location: Prescott, AZ
|
Posted: 12/16/2003, 9:19 am Post subject: |
|
|
|
|
HikerInGilbert wrote: |
I've heard that most of the high-end compasses you can buy in a given location already are set for the average declination. Is this true? |
As azhiker96 stated, some of the high end compasses allow the user to set the local declination manually. What you may have heard is a reference to setting up a compass to allow for magnetic dip. The lines of the earth's magnetic field are parallel to the surface near the equator, and pretty much vertical at the magnetic poles. In between (such as where we are) the lines of the field will be dipping down toward the north magnetic pole. In the southern hemisphere, the lines will dip down toward the south magnetic pole. The closer you get to the magnetic pole, the steeper the lines dip...
Some compass manufacturers allow for this, by arranging the magnets on the compass card (internal disk) so that they dip to the north for compasses sold in the northern hemisphere, and dip to the south for compasses sold in the southern hemisphere.
See:
http://www.suuntousa.com/needle.htm
Hank |
|
Back to top |
|
|
evenstar
Joined: 03 Jan 2003 Posts: 5548 Location: SCW by way of CA
|
Posted: 12/16/2003, 9:52 am Post subject: |
|
|
|
|
My Garmin Etrex Summit can be set for magnetic north or true north and, because it always knows it location on grid, it automatically adjusts the declination. _________________ John Richardson and Richie Rich, El Perro de Playero
http://members.tripod.com/~evenstar/index.html
http://www.arizonahikers.com
When the Man waked up he said, "What is Wild Dog doing here?" And the Woman said, "His name is not Wild Dog anymore, but the First Friend, because he will be our friend for always and always and always. Take him with you when you go hunting."
--Rudyard Kipling, from Just So Stories, 1902 |
|
Back to top |
|
|
plummer150
Joined: 04 Jan 2003 Posts: 542 Location: Jersey City, New Jersey
|
Posted: 1/2/2004, 9:26 am Post subject: re: |
|
|
|
|
Nice, that must be great to have. Wish I had one of them! _________________ "IRONMAN" cometh, hiketh, destroyeth |
|
Back to top |
|
|
BoyNhisDog The dangerous place where the winds meet
Joined: 05 Jan 2003 Posts: 1375 Location: Tucson
|
Posted: 1/2/2004, 9:44 am Post subject: |
|
|
|
|
This is my sweet baby. You can set the declination without messing up the meridain lines in the capsule. It is good for all 5 magnetic zones on this planet supposedly. It did work great in the tropics of Mexico.
Good mirror sighting
I generally keep it set to 11.5 degrees east out here. _________________ Seize from every moment its unique novelty and do not prepare your joys
- Andre Gide |
|
Back to top |
|
|
bzachar
Joined: 10 Feb 2003 Posts: 88 Location: Mesa, AZ
|
Posted: 1/2/2004, 9:57 am Post subject: |
|
|
|
|
evenstar wrote: |
My Garmin Etrex Summit can be set for magnetic north or true north and, because it always knows it location on grid, it automatically adjusts the declination. |
Just an FYI: Every GPSR I've come across has that capability.
Even a unit like the Garmin Legend ($150 after rebate) can be set to True, Magnetic, Grid or User as the North Reference.
Bill |
|
Back to top |
|
|
azhiker96
Joined: 05 Jan 2003 Posts: 1419
|
Posted: 1/2/2004, 2:55 pm Post subject: |
|
|
|
|
I like BoyNhisdog's compass. It's much lighter than the Garmin and doesn't need batteries! I may have to get one. I've been using an older style lensatic compass. It's not as easy to transfer to a map if I want or need to triagulate. |
|
Back to top |
|
|
BoyNhisDog The dangerous place where the winds meet
Joined: 05 Jan 2003 Posts: 1375 Location: Tucson
|
Posted: 1/2/2004, 3:54 pm Post subject: |
|
|
|
|
AZhiker this one will do both well and weighs in at 2 ounces. I find something very satisfying about navigating with magnetized steel. Would love to have a good GPS at times though. They are so good at positioning that it's sort of spooky. Still have not got one though.
Found this one at a very inexpensive price at Forestry Supply. _________________ Seize from every moment its unique novelty and do not prepare your joys
- Andre Gide |
|
Back to top |
|
|
plummer150
Joined: 04 Jan 2003 Posts: 542 Location: Jersey City, New Jersey
|
Posted: 1/11/2004, 6:20 pm Post subject: re: |
|
|
|
|
Nice compass! _________________ "IRONMAN" cometh, hiketh, destroyeth |
|
Back to top |
|
|
JW I'll make rain with my spaceman powers!
Joined: 20 Sep 2003 Posts: 1296
|
Posted: 1/19/2004, 8:15 pm Post subject: magnetic reckoning |
|
|
|
|
BoyNhisDog wrote: |
AZhiker this one will do both well and weighs in at 2 ounces. I find something very satisfying about navigating with magnetized steel. Would love to have a good GPS at times though. Still have not got one though. |
Same here. Dead reckoning with a map, stopwatch and a decent compass is a skill that we should have to back up a GPS. _________________ What a magnificent time to LIVE! - Everett Ruess.
Since my house burned down, I now own a better view of the rising moon. - Masahide. |
|
Back to top |
|
|
Back to top
|
|