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Posted: 12/12/2013 6:20:34 PM EST
Link Posted: 12/12/2013 6:38:56 PM EST

I wouldn't trust myself to measure a 2 degree delta with the Silva. The cheap whistles aren't going to give you better than +/- 5 degrees if you're lucky.

Check-out your lensatic and then trust it.
Link Posted: 12/12/2013 7:38:09 PM EST
I'd trust the lensatic cammenga over anything else.

Google a local orienteering course, or find some local boyscouts that know of one and find a declination station. That's going to be the closest you'll get to confirming it unless you have a buddy with survey equipment.

Also, make sure you know what your magnetic dec is before you go confirm it.
http://www.ngdc.noaa.gov/geomag/img/DeclinationMap_US.png

I already miss being good at that shit.


Link Posted: 12/12/2013 8:53:13 PM EST
[Last Edit: 12/12/2013 8:54:55 PM EST by Country_Boy]
Unless you see snow outside, forget about declanation. By the way, the site airnav.com is a great source for current Wx, sunset/rise times and declanation.

Box the compass. Easiest way is to find somethign square (baseball diamond, city block (walking along the road side of the sidewalk, not against the building, football field, etc. Compass should change 90 deg with each turn. Or layout a fixed bearing with a GPS

2 deg is pretty good accurcary for most "survival" compases, I'd expect better from a USGI Lensatic or one of the better baseplate compases, My Sunyuto clinometer, is good within .5 degree, and the compass on my transit even better.

I've have a mirrored Sunyuto fail, unfortuantaly it was the only compass I had with me on the trip (doing some site surveys, not hiking.) I don't know what demagantized it.
Link Posted: 12/13/2013 5:23:43 AM EST
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Originally Posted By unpleasant:
I'd trust the lensatic cammenga over anything else.

Google a local orienteering course, or find some local boyscouts that know of one and find a declination station. That's going to be the closest you'll get to confirming it unless you have a buddy with survey equipment.

Also, make sure you know what your magnetic dec is before you go confirm it.
http://www.ngdc.noaa.gov/geomag/img/DeclinationMap_US.png

I already miss being good at that shit.
http://imageshack.us/a/img577/3853/n9om.jpg

View Quote

How about printing off a local topo map and checking azimuth and setting declination from local landmarks?

Cheap compasses aren't for geocaching precision, they are for panic azimuth. 5 to 10 degrees accuracy is fine.
"If you get lost, walk in the general north direction, and within five miles miles you will come to the forest service road you parked on. Walk east until you get to the car."
Link Posted: 12/13/2013 8:48:09 AM EST
I personally like the orienteering compasses so I would tend to believe the Silva. The compasses on the whistles are toys and should be treated as such. Just a point based on one of the earlier posts, declination varies much more in an east west direction than north south (at the mid latitudes at least). The zero line is near Chattanooga Tn and just taking a look at a map on my wall, it's 10 degrees east in NM both in the low 30's in latitude.
Link Posted: 12/13/2013 10:41:55 AM EST
USGI lensatic
Link Posted: 12/13/2013 11:20:35 AM EST
Link Posted: 12/13/2013 11:55:43 AM EST
[Last Edit: 12/13/2013 11:56:38 AM EST by RANGER_556]
nevermind...this is not GD
Link Posted: 12/13/2013 12:20:55 PM EST
Link Posted: 12/13/2013 4:58:47 PM EST
[Last Edit: 12/13/2013 5:00:20 PM EST by RANGER_556]
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Originally Posted By TomJefferson:


No its not and we don't really care that you have some non-contributing smart comment either.

Tj
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Originally Posted By TomJefferson:
Originally Posted By RANGER_556:
nevermind...this is not GD


No its not and we don't really care that you have some non-contributing smart comment either.

Tj

Ok, so you brought it on yourself.


Don't offer advice when you have no earthly idea what you're talking about. There is no "calibrating compasses". It either points to magnetic north or it doesn't. If it doesn't , it's a piece of shit.

Calibrating usually means adjusting for true or "grid" north on a mil map.

Honestly, do you have military, specifically infantry, experience?

I got thousands of hours in the woods. Navigating. With a compass.

This is a technical forum. Don't offer "advice" that is incorrect. Being site staff, people will assume you know what you're talking about.

Link Posted: 12/13/2013 5:24:51 PM EST
Actually vehicle (boat, airplane, or car) mounted compasses are calibrated for the vehicle and good hand held compasses are often "set" (dipped) for the angle of magnetic flux
Link Posted: 12/13/2013 5:37:14 PM EST
Check the declination tables for your area.

"North" might be WAY off if you are in some places. Know your area and how to adjust.

Southern WI is 2 degrees off. Get to FIBland and it's different.

Use a sun-stick to get a east/west line and compare to declination and adjust from there.


My bets are the cheap ones are off. Some stuff you could be wearing will cause a field, as will phones, computers, speakers, tvs, shit you have in the basement but can't see cuz you are upstairs, etc.
Link Posted: 12/13/2013 5:38:47 PM EST
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Originally Posted By jchewie1:

How about printing off a local topo map and checking azimuth and setting declination from local landmarks?

Cheap compasses aren't for geocaching precision, they are for panic azimuth. 5 to 10 degrees accuracy is fine.
"If you get lost, walk in the general north direction, and within five miles miles you will come to the forest service road you parked on. Walk east until you get to the car."
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Originally Posted By jchewie1:
Originally Posted By unpleasant:
I'd trust the lensatic cammenga over anything else.

Google a local orienteering course, or find some local boyscouts that know of one and find a declination station. That's going to be the closest you'll get to confirming it unless you have a buddy with survey equipment.

Also, make sure you know what your magnetic dec is before you go confirm it.
http://www.ngdc.noaa.gov/geomag/img/DeclinationMap_US.png

I already miss being good at that shit.
http://imageshack.us/a/img577/3853/n9om.jpg


How about printing off a local topo map and checking azimuth and setting declination from local landmarks?

Cheap compasses aren't for geocaching precision, they are for panic azimuth. 5 to 10 degrees accuracy is fine.
"If you get lost, walk in the general north direction, and within five miles miles you will come to the forest service road you parked on. Walk east until you get to the car."
If it's a new TOPO, sure.

Old, then...well don't. There were some burps in the 90s so some of the maps are off now.
Link Posted: 12/13/2013 6:16:09 PM EST
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Originally Posted By Country_Boy:
Actually vehicle (boat, airplane, or car) mounted compasses are calibrated for the vehicle and good hand held compasses are often "set" (dipped) for the angle of magnetic flux
View Quote



"Dip" is when you are near the north or South Pole. Near the equator the needle should be level.



Again, you're talking to a guy with thousands of hours of navigating by compass.
Link Posted: 12/13/2013 7:38:50 PM EST
According to Ben Meadows (back when they had really good tech support people, and woulc calibrate and reapir surveying equipment) there were 5 different zones for setting dip. The military avoids this by making a compass much deeper than needed, so the center of gravity is well below the dial. However, they are still optomized for the US, they just will work elsewhere. I've seen one (USGI like Cammenga) that was dipped for south american military use, and there was a slight tendancy of it to stick when slighly tiled the wrong way
Link Posted: 12/13/2013 8:08:08 PM EST

2 degrees is 0.56% error - likely more precise than you can navigate. Unless you're flying cross country or directing artillery, I wouldn't be too worried about it...
Link Posted: 12/14/2013 2:26:08 AM EST
[Last Edit: 12/14/2013 2:27:19 AM EST by Mach]
are you outside?

if you are not, then go outside.

if you are get the compass off the ground. yes I know course teach putting the compass on the ground to orient a map, but there are small amounts of iron in everything that will affect a compass slightly.

also 2 degrees may sound like a lot, but on the surface, for every 600 feet you travel if you are off 2 degrees that equates to 20 feet.

you are not going to be able to drive or walk that straight anyway, or find a landmark that close to your travel direction.
Link Posted: 12/14/2013 3:04:42 AM EST
Look up the difference between true north and magnetic north for your location, then go outside tonight and look at Polaris.
Link Posted: 12/14/2013 4:09:43 AM EST
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Originally Posted By Mach:
are you outside?

if you are not, then go outside.

if you are get the compass off the ground. yes I know course teach putting the compass on the ground to orient a map, but there are small amounts of iron in everything that will affect a compass slightly.

also 2 degrees may sound like a lot, but on the surface, for every 600 feet you travel if you are off 2 degrees that equates to 20 feet.

you are not going to be able to drive or walk that straight anyway, or find a landmark that close to your travel direction.
View Quote



Yes, very good advice.


I remember there were several times over my time in the Army that young guys would have their compass resting on the carry handle of their M16 or holding the compass in their hand with some gi-norm-ous metal watch (for SoF door gunners of course) that would slightly skew the compass.

A good compass will always point to magnetic north and marry up in the same direction as another good compass pointing to magnetic north. If one is not, then check the environment. If it's a dud compass compared to a "known good" compass then I'd chuck the compass.

Because like others have said, even if it's just a few degrees off then it's only good for panic azimuths really or telling which way the sun will come up
Link Posted: 12/14/2013 4:16:20 AM EST
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Originally Posted By RANGER_556:

Ok, so you brought it on yourself.


Don't offer advice when you have no earthly idea what you're talking about. There is no "calibrating compasses". It either points to magnetic north or it doesn't. If it doesn't , it's a piece of shit.

Calibrating usually means adjusting for true or "grid" north on a mil map.

Honestly, do you have military, specifically infantry, experience?

I got thousands of hours in the woods. Navigating. With a compass.

This is a technical forum. Don't offer "advice" that is incorrect. Being site staff, people will assume you know what you're talking about.

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Originally Posted By RANGER_556:
Originally Posted By TomJefferson:
Originally Posted By RANGER_556:
nevermind...this is not GD


No its not and we don't really care that you have some non-contributing smart comment either.

Tj

Ok, so you brought it on yourself.


Don't offer advice when you have no earthly idea what you're talking about. There is no "calibrating compasses". It either points to magnetic north or it doesn't. If it doesn't , it's a piece of shit.

Calibrating usually means adjusting for true or "grid" north on a mil map.

Honestly, do you have military, specifically infantry, experience?

I got thousands of hours in the woods. Navigating. With a compass.

This is a technical forum. Don't offer "advice" that is incorrect. Being site staff, people will assume you know what you're talking about.



Listen to the Ranger.
Link Posted: 12/14/2013 5:50:06 AM EST
From my front yard, I can see a radio tower on a mountain top that is about 3 miles away. I have been to this radio tower and marked it with my GPS. Now I can stand in the front yard, "goto" that waypoint wirh the GPS, and it will tell me the correct bearing to that waypoint from where I am at. It is an easy way to check a compass.
Link Posted: 12/14/2013 8:45:53 AM EST
[Last Edit: 12/14/2013 8:51:35 AM EST by TomJefferson]
Link Posted: 12/15/2013 11:08:42 AM EST
[Last Edit: 12/15/2013 11:11:36 AM EST by tc556guy]
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Originally Posted By RANGER_556:
USGI lensatic
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Even those are not always reliable.
We always checked the compasses from supply before sending them out with guys on the annual land nav and there would be one or two out of the box that were not accurate for whatever reason
Link Posted: 12/15/2013 12:11:32 PM EST
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Originally Posted By tc556guy:

Even those are not always reliable.
We always checked the compasses from supply before sending them out with guys on the annual land nav and there would be one or two out of the box that were not accurate for whatever reason
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Originally Posted By tc556guy:
Originally Posted By RANGER_556:
USGI lensatic

Even those are not always reliable.
We always checked the compasses from supply before sending them out with guys on the annual land nav and there would be one or two out of the box that were not accurate for whatever reason


This! I almost blew an EFMB course because of a bad compass. Something I thought could never happen. Luckily I was just practicing before the real thing.

After that my supply Sergeant checked all compasses in supply and found several off by two to three degrees.
Link Posted: 12/15/2013 2:24:37 PM EST
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Originally Posted By WhitewaterRafter:


This! I almost blew an EFMB course because of a bad compass. Something I thought could never happen. Luckily I was just practicing before the real thing.

After that my supply Sergeant checked all compasses in supply and found several off by two to three degrees.
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Originally Posted By WhitewaterRafter:
Originally Posted By tc556guy:
Originally Posted By RANGER_556:
USGI lensatic

Even those are not always reliable.
We always checked the compasses from supply before sending them out with guys on the annual land nav and there would be one or two out of the box that were not accurate for whatever reason


This! I almost blew an EFMB course because of a bad compass. Something I thought could never happen. Luckily I was just practicing before the real thing.

After that my supply Sergeant checked all compasses in supply and found several off by two to three degrees.


You mean you guys didn't just "calibrate them"

Yeah, they do go bad. Usually from Joe banging them around or from being thrown in a box of 30 others and slammed around the supply room.

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