INCORRECT COMPAS BEARING TO REFERENCE TREE

[square nail]

WHAT SHOULD I DO ABOUT A BM I FOUND THAT HAS INCORRECT SURVEY INFORMATION? I FOUND IT 3 INCHES BELOW THE SURFACE WITH A METAL DETECTOR.AFTER THINKING THE BT MIGHT BE 180 DEGREES OF.THE DESCRIPTION STATED "60'4 ft. from station mark in true bearing 173 degrees 04 minutes." I FOUND IT TO BE 60.4 ft at 353 degrees. PID RX1040. THANKS, SQUARE NAIL

[DaveD]

A little piece of surveying trivia for you. Notice that the description says the direction is a "true" bearing. This means it's a geodetic not a magnetic bearing. Prior to the completion of the adjustment of the North American Datum of 1983 (NAD83) by NGS in 1986 all geodetic azimuths or bearings were reckoned from south not north.

[survey tech]

A great example of things that seem obviously wrong, but are in fact correct, given the proper frame of reference.

[square nail]

THANKS YOU GUYS! YOUR HELP IS VERY MUCH APPRECIATED THIS WILL REALLY HELP IN FUTURE SITUATIONS.(AND I THOUGHT I KNEW IT ALL.)

SQUARE NAIL

[+embra]

quote:

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Originally posted by DaveD:

A little piece of surveying trivia for you. Notice that the description says the direction is a "true" bearing. This means it's a geodetic not a magnetic bearing. Prior to the completion of the adjustment of the North American Datum of 1983 (NAD83) by NGS in 1986 all geodetic azimuths or bearings were reckoned from south not north.

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This explains sooo-o-o much! (it also brings up my opinion of those who set these things...Lord, forgive me those uncharitable aspersions I cast.

 

Max

Often wrong but seldom in doubt

[Rhonda_Siminian]

Dave D:

 

> were reckoned from south not north.

 

can you please explain this? I still don't "get it", but it sounds important to know

 

thanks!

[survey tech]

An azimuth is a means of describing a direction. It nust employ some arbitrary line of reference to have any meaning. In land surveying, that line of reference has always been due north. Azimuths measured off that line are described as right north azimuths or left north azimuths, depending on whether they are measured clockwise or counter cloxckwise, respectively, clockwise being the norm. Geodetic azimuths, however, were formerly measured off an arbitrary reference line running due south, also right or left, as the above. Modern adjustments of geodetic data, since the major readjustment of 1983, have switched to right north azimuths, presumably to reduce confusion. This is in the northern hemisphere, in the southern hemisphere the reverse is the case.

[DaveD]

Like so many other things in life, how we reference direction (e.g. fron North, South, East or West) is just a matter of convention. The first Superintendent of the Coast Survey, Ferdinan Hassler was a Swiss trained astronomer and surveyor (Geodesist). Especially in Europe, it was common for astronomers to reference south azimuths (direction) because there are more stars on the south side of the meridian than on the north. We inherited this "convention" from Hassler, and it was changed until NGS completed the readjustment of the North American Datum, called NAD 83 actually completed in 1986. At that time at the request of primarily the surveying community NGS changed the direction of the reference meridian from south to north, as is more commonly used by the public today