Nowadays most watches are dial-less, and therefore the rule should be made from analog into digital.
The Sun is at 15 degrees true * military time (or one hour less if daylight savings time is in effect). A bit more complex formulas apply to sun shadow (add 180 deg), and to the Moon (subtact 13 degrees times number of days since New Mooon).
Yeah, and as to retracing your steps ... most of the time I can 100% trust my dog. It is a fun and useful means of navigation :)
Thanks for the digital rule. If you flesh it out a bit more I will gladly use it in the article.
The Wristwatch compass rule is useful to know whether one uses an analog or a digital watch. From this rule one understands how to approximate directions based on the time of the day. If I know the time of day, but I don't have a watch, I can always scratch a drawing of one into the dirt and approximate directions based on the rule.
FYI, you can use a compass with an inclination gauge to determine your latitude. Point a stick at the North Star, then measure the angle of that stick with a level horizon (a compass with an inclination gauge makes this easy). One may not think this is especially useful, but the inverse can be: The North Star is always located at an angle from your horizon approximately equal (within one degree) to your latitude. Don't bother looking anywhere else for it, and if you think you've found it, but it isn't at that angle, you haven't found it! --mark d.
A very good idea to post that article about something important like this, you did a good job.
zenalpinist - Nov 22, 2007 10:26 am - Hasn't voted
Tip for declination in the west
Great article! We need more people to work on their compass skills rather than their GPS skills.
One way I help people remember to deal with declination in areas to the west of the line (or with East Declination) is the following:
Field to Map: add the declination (and the way to remember is you are going forwards in the alphabet from F to M)
Map to Field: subtract (and the way to remember is you are going backwards in the alphabet from M to F)
Of course it would have to be reversed for those on the east half of the line. Good tips for aiming off too, blindly following the compass or GPS is not always the best way to go.
1) Two other tricks for remembering how declination works help in most of North America. "East is least and West is best." Visualizing the general shape of North America and remembering where the big hole at the top is(Hudson's Bay)--Shezam! roughly where mag North is-- helps this idiot.
2)If the map legend lists a "third north", grid north, the degree or so correction can be added or subtracted from from your declination correction. Not to worry if it's not there, but eliminating cumulative systemic error if it's there. It would be seen as a little set of arrows showing true, magnetic and grid north. Makes setting off the compass very easy by the way.
3)Finally, one may run across a bearing listed like "N67W." This is an alternate convention that is useful where you're doing engineering, surveying or air and sea navigation because it makes trig easier. Unless your curious, ignore it.
http://en.wikipedia.org/wiki/Bearing_%28navigation%29
4)Anything somebody else says is an azimuth is a bearing in our author's sense.
A bearing is a direction gotten from a compass with the quadrant scale (like N37W) while a direction from a compass with 0 - 360 is an azimuth.
The term triangulation is incorrect: this technique is called resectioning and involves the intersection of any two linear features, which can be 2 compass directions but also a road and an elevation, etc.
It seems there was a time when "bearing" was restricted to referring to the direction of a terrestrial object or point. And back then an "azimuth" referred to the direction of a celestial body. That distinction seems to no longer apply.
I'm not sure, but prehaps the military uses the word azimuth instead of bearing.
Look here - one of many sites which use the terms correctly. In fact, when you use 2 compass directions, it is called determining position by intersection, but it comes under resection
This looks really great. I bought a compass but haven't really used it yet, though I haven't needed it yet either. But, at some point I will and I'd like to practice where I can't get lost.
I'm wondering how I can save articles also without commenting for future reference...
Alpinist - Nov 19, 2007 3:56 pm - Voted 10/10
Good ideaNice addition to SP. Thanks for posting it.
vanman798 - Nov 19, 2007 4:14 pm - Hasn't voted
Re: Good ideaYour welcome! I enjoyed brushing up on my compass skills in order to write it.
Dmitry Pruss - Nov 19, 2007 4:22 pm - Voted 10/10
wristwatch as a compassNowadays most watches are dial-less, and therefore the rule should be made from analog into digital.
The Sun is at 15 degrees true * military time (or one hour less if daylight savings time is in effect). A bit more complex formulas apply to sun shadow (add 180 deg), and to the Moon (subtact 13 degrees times number of days since New Mooon).
Yeah, and as to retracing your steps ... most of the time I can 100% trust my dog. It is a fun and useful means of navigation :)
vanman798 - Nov 19, 2007 4:39 pm - Hasn't voted
Re: wristwatch as a compassThanks for the digital rule. If you flesh it out a bit more I will gladly use it in the article.
The Wristwatch compass rule is useful to know whether one uses an analog or a digital watch. From this rule one understands how to approximate directions based on the time of the day. If I know the time of day, but I don't have a watch, I can always scratch a drawing of one into the dirt and approximate directions based on the rule.
Mark Doiron - Nov 21, 2007 3:04 pm - Voted 10/10
Another North Star TidbitGreat article--thanks for this!
FYI, you can use a compass with an inclination gauge to determine your latitude. Point a stick at the North Star, then measure the angle of that stick with a level horizon (a compass with an inclination gauge makes this easy). One may not think this is especially useful, but the inverse can be: The North Star is always located at an angle from your horizon approximately equal (within one degree) to your latitude. Don't bother looking anywhere else for it, and if you think you've found it, but it isn't at that angle, you haven't found it! --mark d.
vanman798 - Nov 22, 2007 12:08 pm - Hasn't voted
Re: Another North Star TidbitGreat tip! I have included it in the article. Thanks a lot.
Corax - Nov 21, 2007 4:41 pm - Voted 10/10
Very comprehensiveGreat addition.
tommi - Nov 22, 2007 6:19 am - Voted 10/10
GreatA very good idea to post that article about something important like this, you did a good job.
zenalpinist - Nov 22, 2007 10:26 am - Hasn't voted
Tip for declination in the westGreat article! We need more people to work on their compass skills rather than their GPS skills.
One way I help people remember to deal with declination in areas to the west of the line (or with East Declination) is the following:
Field to Map: add the declination (and the way to remember is you are going forwards in the alphabet from F to M)
Map to Field: subtract (and the way to remember is you are going backwards in the alphabet from M to F)
Of course it would have to be reversed for those on the east half of the line. Good tips for aiming off too, blindly following the compass or GPS is not always the best way to go.
donhaller3 - Nov 22, 2007 12:18 pm - Voted 10/10
Very good!1) Two other tricks for remembering how declination works help in most of North America. "East is least and West is best." Visualizing the general shape of North America and remembering where the big hole at the top is(Hudson's Bay)--Shezam! roughly where mag North is-- helps this idiot.
2)If the map legend lists a "third north", grid north, the degree or so correction can be added or subtracted from from your declination correction. Not to worry if it's not there, but eliminating cumulative systemic error if it's there. It would be seen as a little set of arrows showing true, magnetic and grid north. Makes setting off the compass very easy by the way.
3)Finally, one may run across a bearing listed like "N67W." This is an alternate convention that is useful where you're doing engineering, surveying or air and sea navigation because it makes trig easier. Unless your curious, ignore it.
http://en.wikipedia.org/wiki/Bearing_%28navigation%29
4)Anything somebody else says is an azimuth is a bearing in our author's sense.
singularity - Nov 26, 2007 3:32 pm - Voted 10/10
very usefullthx for adding it!
MakeItHappen - Nov 26, 2007 7:47 pm - Hasn't voted
Good articleYet another reason why SP is such a useful and helpful website.
Moni - Nov 28, 2007 1:28 pm - Voted 10/10
Good jobNicely done.
I take issue with two terms, however.
A bearing is a direction gotten from a compass with the quadrant scale (like N37W) while a direction from a compass with 0 - 360 is an azimuth.
The term triangulation is incorrect: this technique is called resectioning and involves the intersection of any two linear features, which can be 2 compass directions but also a road and an elevation, etc.
See here
vanman798 - Nov 28, 2007 3:03 pm - Hasn't voted
Re: Good jobSynonyms. :)
It seems there was a time when "bearing" was restricted to referring to the direction of a terrestrial object or point. And back then an "azimuth" referred to the direction of a celestial body. That distinction seems to no longer apply.
I'm not sure, but prehaps the military uses the word azimuth instead of bearing.
Moni - Nov 28, 2007 8:10 pm - Voted 10/10
Re: Good jobIt is not an opinion.
Look here - one of many sites which use the terms correctly. In fact, when you use 2 compass directions, it is called determining position by intersection, but it comes under resection
Resection
Azimuth
dpk - Nov 30, 2007 11:01 pm - Voted 10/10
very helpfulgreat detail and links - an excellent reference tool
thank you
idahomtnhigh - Nov 30, 2007 11:38 pm - Voted 10/10
Great articleI teach a land navigation class and I think or article was well done, Thanks for the post.
vanman798 - Dec 13, 2007 12:16 pm - Hasn't voted
Re: Great articleThat is a great compliment coming from a land navigation teacher. Thank you very much.
cp0915 - Dec 7, 2007 1:18 pm - Voted 10/10
AmazingYou did a terrific job on this page! Excellent, truly.
chel3178 - May 31, 2008 10:39 pm - Voted 10/10
Very DetailedThis looks really great. I bought a compass but haven't really used it yet, though I haven't needed it yet either. But, at some point I will and I'd like to practice where I can't get lost.
I'm wondering how I can save articles also without commenting for future reference...