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headmj

What is NNE SSW etc?

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I have been reading the data sheets and the surveyors when giving directions never give a degreed compass bearing. I have been looking aroung but can't find a definition of the descriptions they use. For example, is north-northeast 22.5 degrees? Just trying to make sure I understand this. It is weird what little gaps we find in what we know. icon_biggrin.gif

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quote:
Originally posted by headmj:

For example, is north-northeast 22.5 degrees?


 

Good assumption, It's a simple as that! Halfway between one and the other. Hear them terms a lot in old pirate movies, have heard a few sailors around here use them too.

 

Guess they couldn't count to 360º, so used the 16 direction system to get by!

 

Some days you're the dog, and some days you're the hydrant.

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Well, you can go to 32 points with stuff like North by East, which is 11.25 degrees! This shows it all:

http://education.qld.gov.au/tal/kla/compass/html/cobox.htm

 

I doubt the NGS would find the humor in using things to this level of precision in reports. icon_smile.gif I am amazed, though, that surveyors don't use bearings all the time to landmarks and just use the 8 point compass terminology (at least around here). Mabe to them, just using just 8 points is somehow elegant.

 

Then, of course, there's grads (400 degrees to a circle) and even mils (6400 to the circle).

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Quad numbers never get above 90. They increment up to 90 as the compass swings from North to East and then back to zero as the compass swings from East to South, then repeats the process as the compass swings from South through West and onto North. Thus a Quad bearing can never be more than 90. North and Sounth are 0 / East and West are 90. This is the reason for entrys like "N32W" on the data sheets.

 

Why use a system like this? A good look at the Trig tables will answer this question.

 

A great page for all this is...

http://www.kooters.com/sezbrntn.html

 

>Personally Responsible for the Recovery of .00217% of the Benchmark Database!<--watch this number!

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Thanks for all of your help. Both websites are really helpful and the Kooters site is just plain hilarious!! icon_wink.gif

 

I think I'll go box my compass now!! icon_biggrin.gif

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BDT

This is another case where the distinction between horizontal and vertical control points is significant. Surveyors normally provide precise directions to nearby stations, azimuth marks and reference marks, usually in degrees and minutes format, when using a horizontal control station. This is because the purpose of such a station requires this level of precision. When using a vertical control station, directions may be given using the cardinal and sub-cardinal nomenclature discussed above. This is because vertical control points have no precisely measured location and therefore the use of precise directions in such cases would be meaningless. The directions referred to may have been merely estimated by eyeball, so specifying them to the nearest degree would be ridiculous. It is a commonly observed principle among surveyors not to state results in an artificial manner, so one can generally assume that a measurement written in a precise form was precisely measured and likewise a measurement written in an approximate form was estimated. Geodetic surveyors have no use for the standard magnetic compass, since their work is always based upon true astronomic north, which often varies from magnetic north by several degress and the relationship between the two is constantly in flux due to the dynamic composition of the earth.

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quote:
Originally posted by Black Dog Trackers:

Well, you can go to 32 points with stuff like North by East, which is 11.25 degrees! This shows it all:

http://education.qld.gov.au/tal/kla/compass/html/cobox.htm


 

Well, guess you got me on that one, never heard of the other 16. Guess I gotta stop getting all my wisdom from old pirate movies!

 

Some days you're the dog, and some days you're the hydrant.

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quote:
Originally posted by brdad:

Guess they couldn't count to 360º, so used the 16 direction system to get by!

 


 

Oh, you MUST check out THIS BOOK!

 

ApK

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