[rogerstevens]

Hey guys I have some usgs topo maps from 1699 and I´m wondering how much the magnetic declination has changed since then is there going to be a noticable difference ?

[crazydave]

1699 did they have magnetic and true north back then? hang on that cant be right as there was no USGS.

try this -

Magnetic Declination (Variation) Home

[rogerstevens]

Originally Posted by crazydave

1699 did they have magnetic and true north back then? hang on that cant be right as there was no USGS.

try this -

Magnetic Declination (Variation) Home

This is exactly what I was looking for! NOAA's Geophysical Data Center - Geomagnetic Data

Thanks! (PS I meant to say 1966 :D)

[Celticwarrior]

Yeah, I think you meant 1999? The motion of the magnetic north pole since 1999 has moved about 3 degrees North by 6 degrees West, which isn't enough to be statistically significant in most land orienteering. Aircraft and ocean vessels are a different animal though.

If you meant 1699 and that topo map has GPS coordinates, let me know. I think we should contact Erich von Danniken about those ancient astronauts he wrote about, and see what he says. LOL

[crazydave]

if its similar to here then make a note and keep in mind that you will allways be slightly off.

this should mean that if you want to intersect a wall for example and the visability is poor then you can march on your bearing with the knowledge that when you hit the wall the gate is to the left.

if that makes sense.

its losing .3 of a degree a year or something like that, apparently it will eventually flip completely then your compass will point south for a few thousand years.

[rogerstevens]

Thanks for the info guys

I wish i had some maps from 1699 thats some serious bucks:D

[crazydave]

well it would have a lot of blank spaces and some here be dragons around the edges. it would also be an OS map just like the ones we did of india :)

[Pat/Rick]

Those were the maps McKenzie used when he explored western Canada. (just funnin')