Angle of declination

[Nessmuk]

When I taught navigation, I often started the first lesson with an imaginary flight to Alaska.

I like it. I may use that scenario in my next SAR navigation training class.

 

[iagreewithjamie]

SARDOG: Given your experience, I'm hoping your "toss the compass" comment was a joke.
Even if you don't know where you are, one of the biggest challenges to people who are disoriented and try to "find their way out" is that they commonly wind up walking in circles (lots of blindfold tests have been done with humans, and our innate ability to wander aimlessly in circles while thinking we're going somewhere). Even if you can't use a compass to help determine where you're going, you can at least use it to make sure you stay moving forward (and that is a function that is independent of declination)

So as not to be a schmuck who quotes "studies" and gives no reference... here's one of many:
http://www.reuters.com/article/2009/08/20/us-circles-idUSTRE57J4I620090820

 

[Nessmuk]

SARDOG: Given your experience, I'm hoping your "toss the compass" comment was a joke.
Even if you don't know where you are, one of the biggest challenges to people who are disoriented and try to "find their way out" is that they commonly wind up walking in circles (lots of blindfold tests have been done with humans, and our innate ability to wander aimlessly in circles while thinking we're going somewhere).

I'm sure SARDOG was simply making the same point I was getting at. A compass alone with no other geographic information is of little value - although that could change over time if information becomes available to you. So in practice I wouldn't necessarily throw the compass away.

You might find this NPR video about walking in circles interesting. I show it during my navigation training classes.

 

[sardog1]

SARDOG: Given your experience, I'm hoping your "toss the compass" comment was a joke.
Even if you don't know where you are, one of the biggest challenges to people who are disoriented and try to "find their way out" is that they commonly wind up walking in circles (lots of blindfold tests have been done with humans, and our innate ability to wander aimlessly in circles while thinking we're going somewhere). Even if you can't use a compass to help determine where you're going, you can at least use it to make sure you stay moving forward (and that is a function that is independent of declination)

So as not to be a schmuck who quotes "studies" and gives no reference... here's one of many:
http://www.reuters.com/article/2009/08/20/us-circles-idUSTRE57J4I620090820

There is zero point to attempting forward progress in Alaska if you have no idea where you are. It ain't New Hampshire or New York – you stand a real good chance of hypothermia, starvation, injury or being consumed by the top of the food chain before you hit a road, a pipeline, a river with boat traffic or a railway. In the scenario I described, you're far better off building a hellacious big fire and waiting for someone to come investigate the smoke. This technique would probably have saved Chris McCandless, for instance.

 

[TJsName]

I like it. I may use that scenario in my next SAR navigation training class.

Just make sure they know that that makes them liable to be fined for any rescue.

 

[DougPaul]

The right answer? Throw the compass away– it's just extra weight that serves no purpose in this scenario if you don't have a map or least some prior knowledge of the terrain.

Even if you have a set of maps covering the entire state, the compass is likely to be useless because you are likely to get a number of local terrain matches. An astrolabe might be more useful (even if you have to make it yourself)...

A watch and visible sun could replace a compass.

While the best tools would be a chronometer and sextant or the (Luddite-hated) GPS, a broadcast band radio might be useful as an improvised radio direction finder. (Note that the paths radio signals can be bent by propagation conditions.)

Doug

 

[Nessmuk]

Just make sure they know that that makes them liable to be fined for any rescue.

We're the rescue-ers, not the rescu-ees.
In most cases it is better to have the lost stay put anyway.

 

[Nessmuk]

While the best tools would be a chronometer and sextant

... and a current celestial almanac, and a copy of the aptly named "sight reduction tables". I have spent many hours peering through a sextant, many more hours reducing the calculations to crossed lines of position on my chart, including over Alaska and points further north.

But as you pointed out, you can do a lot with the sun alone (with a stick), and knowledge of a few stars, including Polaris of course. You could probably get a good idea of your latitude to within a few degrees by estimating the elevation of Polaris. A piece of paper folded into a triangle gives you 45 degrees, twice folded gets 22.5 degrees, again to half of that. Eyeball further angular divisions of your paper sextant. Check your work with that compass that you didn't throw away.

 

[DougPaul]

But as you pointed out, you can do a lot with the sun alone (with a stick), and knowledge of a few stars, including Polaris of course. You could probably get a good idea of your latitude to within a few degrees by estimating the elevation of Polaris. A piece of paper folded into a triangle gives you 45 degrees, twice folded gets 22.5 degrees, again to half of that. Eyeball further angular divisions of your paper sextant. Check your work with that compass that you didn't throw away.

One can, of course, get true north as well as one's latitude from Polaris.

And with a watch and some sticks to track the sun (to estimate solar noon) you might be able to make a reasonable estimate of your longitude.

Once you have a reasonable guess of your location, then the compass might be even useful for more than just as a protractor. (Calibrate the declination from the true north derived from Polaris.)

Note:
We should note that the bulk of Alaska is ~13 deg N-S and ~28 deg E-W and an approximate location could be useful. In contrast the WMNF is ~.8 deg N-S and ~1.2 deg E-W and the methods described above are likely to be less useful.

Doug

 

[sardog1]

We're the rescue-ers, not the rescu-ees.
In most cases it is better to have the lost stay put anyway.

As long as this thread has drifted off course (yes, that's an intentional pun), I'll add this as a reminder to all of us.

A search for a missing person in WA had ended successfully, and the searchers were instructed by radio to return to base. Everyone made it back soon except a single dog handler. (This was back in the day when working alone was pretty common.) He reported his progress as they waited, but his transmissions got weaker and weaker.

Eventually there was enough concern that a helicopter was sent to look for him. When they found him, he was on a course for Canada. While using his orienteering style compass to follow a heading, he'd mistakenly pointed the direction of travel arrow on the base at his navel, instead of in front of him. This meant he was constantly traveling in the direction opposite to what he intended. It's probably the most common error with this type of compass.

(And no, it wasn't me. I would have died from embarrassment and not been here to tell the story.)

 

[John H Swanson]

As long as this thread has drifted off course (yes, that's an intentional pun), I'll add this as a reminder to all of us. A search for a missing person in WA had ended successfully, and the searchers were instructed by radio to return to base. Everyone made it back soon except a single dog handler. (This was back in the day when working alone was pretty common.) He reported his progress as they waited, but his transmissions got weaker and weaker. Eventually there was enough concern that a helicopter was sent to look for him. When they found him, he was on a course for Canada. While using his orienteering style compass to follow a heading, he'd mistakenly pointed the direction of travel arrow on the base at his navel, instead of in front of him. This meant he was constantly traveling in the direction opposite to what he intended. It's probably the most common error with this type of compass. (And no, it wasn't me. I would have died from embarrassment and not been here to tell the story.)

I often us copies of gridded topo maps and use the grid for deriving the desired bearing. And since many times the map is folded and inside a ziplock on more than one occasion what I thought was the N on the map was E or W or S. So I have lived through a similar error.

 

[RoySwkr]

There is zero point to attempting forward progress in Alaska if you have no idea where you are.

Surely there are occasions when it is better not to stay put even if you don't know where you are. Obviously if you are short of food there are reasons to conserve energy but depending on circumstances you may not be in best place:
* Move downhill if no water where you are
* Move to open area to be more visible
* Move away from grizzly concentration area

And while you don't know the direction to nearest road, cabin, etc. you know it's not where you are so by heading elsewhere you increase your chance (from zero!) of finding such plus if you leave directional markers where you were you also increase your chance of being discovered by passers-by

There is a famous book "Sands of the Kalahari" [note that the movie is quite different] where survivors of a plane crash set off one by one to all compass points figuring that's the best way to find help that could then rescue everybody, IIRC they find out that they weren't actually even in the Kalahari but in a nearby desert that didn't make as nice a book title

 

[iagreewithjamie]

How do you know where a grizzly concentration area is without encountering grizzlies first?

 

[JCarter]

Look for the piles of scat full of bear bells

 

[DougPaul]

How do you know where a grizzly concentration area is without encountering grizzlies first?

Local features... Eg:
* berry patches
* streams with fish
* thickets (poor visibility)
* holes where a bear has dug for ground squirrels
* scat
* tracks
* animal paths
* sightings
* anywhere else a grizzly wants to visit

Doug

 

[hikerbrian]

While using his orienteering style compass to follow a heading, he'd mistakenly pointed the direction of travel arrow on the base at his navel, instead of in front of him. This meant he was constantly traveling in the direction opposite to what he intended. It's probably the most common error with this type of compass.

Yes, I think it's a very common error to make.

To avoid this potentially fatal error, I tell my students to make an estimate of their desired direction of travel, as a first step, by simply looking at their map (do I want to go roughly S, 180 degrees, or NE, 45 degrees, etc). After taking a bearing, the bearing should be compared to the estimate; it's very easy to recognize if you're off by 180 degrees. And if your life depends on it, you really don't want to be off by 180 degrees.

Edit: on rereading sardog's synopsis above, it sounds like the person was actually holding the compass backwards. This is different than the mistake I was outlining above. I've never actually heard of that happening, but I suppose it could happen with an "orienteering style" compass, on which the direction of travel arrow might not be so obvious. Sorry for the confusion.

 

[Nessmuk]

To avoid this potentially fatal error, I tell my students to make an estimate of their desired direction of travel, as a first step, by simply looking at their map (do I want to go roughly S, 180 degrees, or NE, 45 degrees, etc). After taking a bearing, the bearing should be compared to the estimate; it's very easy to recognize if you're off by 180 degrees. And if your life depends on it, you really don't want to be off by 180 degrees.

The name I give to that very quick thought process is making a "sanity check". A good practice to always have in many applications to prevent the head slap when you realize a stupid mistake.

 

[John H Swanson]

I include the practice of saying the bearing aloud. On one occasion while I was the sole person navigating I had one in my party say that doesn't sound right. And if people are co navigating or following along then they a likely to give that sanity check