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Zurcher

Compass Rose

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On the benchmark data sheets, seldom see anyone using magnetic bearings? in common use are old fashioned

marine compass designations such as : its NNE or NE but nothing more accurate than every 22 1/2 degree increments! As an example: if it says NNE, its 22 1/2 degrees on my compass and I supose need to be corrected to a TRUE bearing? I have noticed that many / most bearings not very accurate? Do the surveyors [ seems to me ] just say" its over there, about north? " and not bother with magnetic bearings? [ Yes, we know the declination changes over the years! ] but whats a guy to do? standind there, gotta start with the trusty old boyscout compass.

z

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Our experience. which is less extensive than that of many others here, is that unless they are specified as magnetic, bearings are to be taken as from true north. Local declination for a given area can be found without too much trouble. The vagueness you mention usually does not extend to such items as reference and azimuth marks. Even if they are described as NNE or the like in the descriptions, the "box score" section of the data sheet gives metric distances and azimuths at least to the minute.

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I have a Question.My GPS can be set to true or magnetic North.Which is the best for Geocaching and finding surveying markers ?

Have a nice day

johnboy11171

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It depends. If you're using a magnetic compass to take bearings, then it's easier to set the GPS to magnetic. Otherwise true is fine. In some areas, there is little difference between the two, and in some there is a huge difference. Depends on where you are. If you're looking for an object, whether it's a geocache or a survey marker, it really makes little difference which you use, you just follow the GPS, either by going in the direction of the arrow or keeping your heading as close to the bearing as possible. Generally, it isn't very important.

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On the benchmark data sheets, seldom see anyone using magnetic bearings? ---

 

Off the road and back in the Yuma AZ area for a few days before starting my northward migration. Got a bunch of photos

to upload and NGS recoveries to submit; but do have an immediate question that kind of fits this old thread.

 

I run across several marks that used 'magnetic' in the description. I'm wondering if the headings were changed

when the Data Sheet format was instituted but leaving the word 'magnetic' in?

 

CZ2260'REFERENCE MARK NO. 1, A BRASS CAP SET IN CONCRETE BLOCK 7 BY

CZ2260'12 BY 30 INCHES SET 26 INCHES IN GROUND, IS 146.975 METERS

CZ2260'(482.20 FEET) EAST (MAGNETIC).

 

38f061e3-3557-4c94-9e6d-88b50b62b083.jpg

 

1914 GLO RM 1

 

This RM 1 was found (POOR condition) at the given distance but due east of the GLO. The NOAA calculator gives a 14 degree variation for that

location in 1936. Since I found this one right on the true bearing I did not bother to calculate a correction for any others.

 

Am I trying to make too much out of this? kayakbird

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Am I trying to make too much out of this? kayakbird

Wait.. it's laying on its side, and you're considering that 'poor'? Or am I missing something (*entirely* possible)? :)

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Am I trying to make too much out of this? kayakbird

Wait.. it's laying on its side, and you're considering that 'poor'? Or am I missing something (*entirely* possible)? :)

 

Yep, I have seen evidence of marks, and I think documentation of a famous Station back east, that have had clean breaks Super-glued

and are still 'GOOD' in the system. It is only an RM. Just poke around a little, put it back on it's base and use a true bearing

due west to find the GLO the next time there is a foot of snow. MEL (grinning)

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Am I trying to make too much out of this? kayakbird

Wait.. it's laying on its side, and you're considering that 'poor'? Or am I missing something (*entirely* possible)? :)

 

Yep, I have seen evidence of marks, and I think documentation of a famous Station back east, that have had clean breaks Super-glued

and are still 'GOOD' in the system. It is only an RM. Just poke around a little, put it back on it's base and use a true bearing

due west to find the GLO the next time there is a foot of snow. MEL (grinning)

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Here is a quote on the subject from USC&GS Special Pub. #247, pages 118-119:

"The bearing to the nearest of the eight points of the compass is entered by the letter abbreviation (as N, NE, E, SE, etc.). Ordinarily all bearings should be referred to the true meridian, but magnetic bearings may be shown if labeled "(mag.) ."

 

George L

NGS, Retired

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Since this is actually a GLO corner, you can probably find the GLO/BLM notes for it and get the actual true bearing (to about the nearest minute to the RM's.

 

- jerry

 

On the benchmark data sheets, seldom see anyone using magnetic bearings? ---

 

Off the road and back in the Yuma AZ area for a few days before starting my northward migration. Got a bunch of photos

to upload and NGS recoveries to submit; but do have an immediate question that kind of fits this old thread.

 

I run across several marks that used 'magnetic' in the description. I'm wondering if the headings were changed

when the Data Sheet format was instituted but leaving the word 'magnetic' in?

 

CZ2260'REFERENCE MARK NO. 1, A BRASS CAP SET IN CONCRETE BLOCK 7 BY

CZ2260'12 BY 30 INCHES SET 26 INCHES IN GROUND, IS 146.975 METERS

CZ2260'(482.20 FEET) EAST (MAGNETIC).

 

38f061e3-3557-4c94-9e6d-88b50b62b083.jpg

 

1914 GLO RM 1

 

This RM 1 was found (POOR condition) at the given distance but due east of the GLO. The NOAA calculator gives a 14 degree variation for that

location in 1936. Since I found this one right on the true bearing I did not bother to calculate a correction for any others.

 

Am I trying to make too much out of this? kayakbird

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