True North or Magnetic North?

[KNITELY]

Hello Newby Here,

 

Should the GPS be set to True North or Magnetic North? I have an older one , it's a Magellan Meridian Gold.

 

Thank you, Pete

[NordicMan]

Choosing "Magnetic north" will probably do for 99% of Geocaching activities.

 

But if using the GPSr with a map, then true north might be more accurate. You need to know the declination variance for your area in order to use true north

[KNITELY]

Choosing "Magnetic north" will probably do for 99% of Geocaching activities.

 

But if using the GPSr with a map, then true north might be more accurate. You need to know the declination variance for your area in order to use true north

 

Thank you, that maybe the reason i couldn't find the cache, I was looking for.. Thanks again....Pete

[+WhatWasIThinkin]

I use Magnetic North in my Meridian Gold and find that im acurate to with-in @15 feet.

[+Coyote's Girl]

I use true north on mine and do well enough. KNowing the declination for your are will help if you use magnetic north. Here in St. Louis, it's close to zero but if you lived in Alaska, well, it'd be a little crazy. Have fun!

[+Markwell]

Here's an article I wrote a while ago...

 

http://www.markwell.us/geofaq.htm#truemag

[+StarBrand]

It does not make a hill of beans worth of difference which one you are set to for the vast majority of Geocaches. The only time it matters is on offset caches where they instructions are something like "project a waypoint at 124 degrees - 299 feet away" - then you need to know if they are talking off of true north or magnetic north.

[+Markwell]

In the continental United States, the declination at the extremes is only somewhere between 18° E (near Seattle) and 18° W Near the far eastern part of Maine).

 

If someone had you finding a cache in Duncan, British Columbia up by Seattle, the current magnetic declination is about 18° E. Using StarBrand's example of 299 feet, starting at N 48.80246° W 123.70627°, if I project a waypoint with True North at 124 degrees, I would get N 48 48.120, W 123 42.314. If I adjust my magnetic declination 18° (106°), I would be at N 48 48.134, W 123 42.305. The N 48 48.120, W 123 42.314 and N 48 48.134, W 123 42.305 is 95½ feet.

 

However, most of the US is less than 16° and that would bring that variance at that distance to around 80 feet.

 

Usually with distances that are projected with waypoints, (less than 100 feet) and declinations in the U.S. of <16°, you'll only be off by around 30 feet when you reach your target. Guess what - a GPS can be off by at least 30 feet as well.