Compass Question

[+Mastifflover]

Ok I asked this question in another thread but it was getting lost so I will ask again for me and the other compass newbees. If I buy a compass with a movable pointer do I just orient the compass pointer to the direction that the arrow on my gps is pointing and then just follow the compass if signal gets spotty or nonexistant on my gps? Thanks in advance!

[+Poindexter]

No. Face the direction to the cache as indicated by your pointer on your GPS compass page while moving. Now hold your compass in front of you and rotate the dial until the pointer is over the compass needle (this is called boxing the needle). Now continue in a direction that keeps the needle boxed while properly orienting the compass in front of you.

[+Mastifflover]

Ok thanks I think I have it now!

[+The Leprechauns]

In a place where you have good GPS signal, look at your GPSr's compass page and note the bearing to the cache (a point on the compass between 0 and 360). Let's say the cache is .2 miles away at a bearing of 47 degrees. Then, take out your compass and move the outer ring until the mark on the compass base lines up with 47. (This assumes you have a decent compass with a moving thingie that you can turn. I'm also assuming that your GPS is set on magnetic north, so that you don't need to adjust your compass for the local declination between magnetic north and true north.)

 

Next, line up the north arrow on your compass with the outline of the arrow. The "front" of the compass, with the mark aligned to 47 degrees, will now be facing the cache. Walk in that direction.

 

Assume that the trail takes a turn, or there is a gully or pile of boulders blocking the straight line drawn between your position and the cache at a bearing of 47 degrees. Unless you're adventurous or stupid, you'll want to avoid these obstacles. Whenever you deviate from the intended bearing, the direction you're traveling is called your heading. You'll need to keep track of these detours. Before navigating around that gully, pick a landmark on the opposite side, like a large rock, or a lone evergreen tree mixed in with the regular trees. When you finish your detour, "get your bearings back" by going to your landmark and checking your compass again.

 

Of course, you can also re-adjust your bearing by comparing the GPS to the compass multiple times along your trip. In orienteering, we check against a map rather than against a GPSr. When I am geocaching in poor satellite reception conditions, like during a rainstorm, I'll orient my compass before I leave a clear hilltop and plunge into heavy tree cover or the bottom of a rocky ravine.

 

In geocaching, I've found my compass to be most useful during the last 200 feet between me and the cache. My GPSr does not have a real built-in compass, so when I get very close to the cache and I start wandering around in circles, the GPSr becomes confused and will point in the "wrong" direction. A quick check against the compass makes me sure that I'm walking 40 feet in the correct direction.

 

Hope this helps!

[+Mastifflover]

I just checked and my gps a garmin legend was set to true north I changed it to magnetic north and a box below it says 010 deg.W do I need to change that or leave it alone?

 

Edited: for says not syas

Edited January 15, 2004 by Mastifflover

[+Alphatexana]

Your GPSr (assuming that it doesn't have a built-in compass--and with the Legend, you don't) can only tell you what the bearing (direction) is between where you are and where you are going when you are standing still. In other words, the GPSr has no way of knowing which way you are facing. This is why you need to be moving in order for it to know what your heading is. By moving, your GPSr is able to figure out (1) where you were a moment ago, (2) where you are now, and (3) the direction to where you are wanting to go (and your GPSr will even point the way).

 

A good link to check out for more explanation isMarkwell's FAQ.

 

Once you know your bearing (make sure you have your GPSr set to use magnetic north), you should be able to turn the large dial of your compass to that heading, match up the north end of the needle toward the north part of the compass body, and figure out where you need to head.

 

This is a drastically simple explanation of using a compass. I'd check out these links for more information:

 

How to Use a Compass

 

Chasetek's How to Use a Compass

 

Good Luck,

 

Alphatexana

 

(edited to reference Legend)

Edited January 15, 2004 by Alphatexana

[+The Leprechauns]

Mastifflover, I think that your GPS is just telling you that the angle of declination between true north and magnetic north at your location is 10 degrees to the west. Since you've switched to magnetic (which you should, unless you have a fancy compass that permits declination adjustment), your GPS is just reminding you that true north is 10 degrees off. This would be important if you were working with a map.

 

In addition to the helpful links above, here is a really short summary of GPS and compass use on a USGS website.

[+Mastifflover]

Ok I think that I am ready to go geocompassing, I mean geocaching with the aid of a compass. Thanks for the help.

[dave and jaime]

Mastifflover, I think that your GPS is just telling you that the angle of declination between true north and magnetic north at your location is 10 degrees to the west. Since you've switched to magnetic (which you should, unless you have a fancy compass that permits declination adjustment), your GPS is just reminding you that true north is 10 degrees off. This would be important if you were working with a map.

 

In addition to the helpful links above, here is a really short summary of GPS and compass use on a USGS website.

are you sure of this?

[+The Leprechauns]

are you sure of this?

Nope. That's why I included the words "I think..." at the beginning of my post. I don't use the same GPSr and I'm not familiar with the feature that mastifflover described. I gave what I thought to be a plausible answer. Do you have a better explanation? Please share!

 

I am, however, pretty sure about my compass advice.

[dave and jaime]

are you sure of this?

Nope. That's why I included the words "I think..." at the beginning of my post. I don't use the same GPSr and I'm not familiar with the feature that mastifflover described. I gave what I thought to be a plausible answer. Do you have a better explanation? Please share!

 

I am, however, pretty sure about my compass advice.

as for the compass i have a mag315 but i think the design is similar in that there is a outer ring that rotates to give cardinal directions an arrow head at the center to indicate your current direction and an arrow inside the ring that rotates to indicate the direction to the point your are heading to .

 

ok, i never gave any consideration to the question but i hoped you were right. as for the declination, i thought about it and to find your declination is simple---simply record your bearing to any point some distance away change the north reference and record your bearing again. the difference in the 2 'bearings' is your declination.

[+Tprints]

Hey Mastifflover, I just met you the other day but unless my memory is really fading, I don't remember you looking like your photo here!

[+Mastifflover]

Your memory isn't that bad thats my dog Hannibal. He's a 165 lb baby!! He goes with me when I geocache in the woods.