Basis of Bearings, rides again.

nate-the-surveyor · 2015-10-12T16:59:00Z

Basis of Bearings:Geodetic NorthGrid NorthAssumed NorthTaken from Previous SurveyFrom Deed This is one item, that I feel is pivotal in the integration of our services, with the world, that is deserving of more time and attention, than it has gotten in times past.I can remember performing all the field work, (via Transit and tape, or Total Station, etc) and finally coming down to the end, and asking my dad, "Dad, what basis of bearing are we going to use for the final presentation?" He'd tell me the East line of the previous survey for _____. Or the like. I'd rotate to that bearing, and publish that this was the basis of bearing. There was a court case in NW Arkansas, where Jack Stiffler was involved. He became known as "Jack, Rotate-your-bearings, Stiffler", to the court. The attorneys were having a hay day with the fact his basis of bearings were not the same as some other survey. This illustrates the need to simplify for the general public this item. The Tax Assessors, and Title companies need to be able to work with this. They often have no idea as to what a land survey is, and is not. Nor do they know the difference between "Putting the deed on the ground" or "Taking the the ground, and putting it on the plat". Or a mix and match of the 2 above concepts. The fact is that almost all surveys are done "In GRID". That is, it is on a SINGLE RECTANGULAR system. If the plat says Basis of Bearings is Geodetic, or True north, then all that means is that at ONE place of that grid, it has been oriented to True north. As you move East, or West, it is NO LONGER on true north. That is only true, at one place on that survey, and on a radial line, from that point to the theoretical north pole. When somebody publishes a plat, on True North, then they go and do a survey 1 mile to the east, (With another base station, and projection) and they both are on True North, then this means that they actually did a survey on two different Grids, wherein they were both oriented to the North Pole, at SOME POINT in their Grid. However, these two grids are not on the same bearings! There is an exception to this. The BLM does their work on a semblance of a grid. They also use Least Squares, (Which is a really fine adjustment program). . Then, AFTER all decisions are made, ALL the individual lines are rotated, to be oriented to TRUE north. This was via an act of Congress! Thus a line that reads N 89å¡12'W 80.01 chains, on one of their plats, would read S89å¡13'E 80.01 chains, IF it were labeled going East, instead of going West. Those BLM boys really freak out bearing systems, by this means. Because they round the bearings to the closest minute of arc. AND then they try to run the final rounded dimensions in a rectangular system computational device, to SEE IF IT CLOSES, after all that jacking around, to meet the Congressional standard! Sometimes they then ADJUST THINGS ONE MORE TIME, so that it will close, within min standards! This leaves some slop on all the published values of the BLM. Needless slop. I wish they would PUBLISH it in ONE rectangular system, with a published theta, to convert it to TRUE north. Or to State Plane Grid North. All this work, to meet an outdated standard. And, MANY connoisseurs of RTK GPS publish plats "On true north". Yet, they do not know what just happened. That survey is ON TRUE bearings at the BASE station, and on a radial line to and from the north pole, at that point. Yet, they are working on a rectangular Grid, which is on TRUE at one location. Then, they move their base station, and low and behold, it's NO LONGER on the same bearings! I had a surveyor, who is a real gentleman, and a decent guy, ask me WHY his bearings from A-B, did not match his bearings from B-A, when he moved his base. It took some work, but he got it. Many folks have never bothered to ask, or even care to ask. This is an illustration of the literal application of an outdated law, messing up a perfectly good survey. BTW, the BLM COULD publish two plats, one of them to meet the Congressional standard, and another that is on State Plane Grid bearings, to get rid of all that jacking around. I am simply bringing it up, because it is a "Pivotal" (No pun intended, you know, Jack Rotate-your-bearings Stiffler) issue, at the junction of Land Surveyor, to Land USER. And, I feel that it should be addressed more directly. And, SIMPLIFIED for the general public. I'd like to see legislation that REQUIRES all surveys in the State of Arkansas to be:1.) On an objective* basis of bearings. 2.) Or referenced to an objective* basis of bearings. * Objective Basis of Bearings means that the plat is oriented to State Plane Grid Bearings, or True bearings. IF it is oriented to TRUE, then the LAT LON must be also published, where the sunshot, or GPS base was set. Or a Theta angle to Grid can be published. If it is oriented to DEED, or previous Plat, then it has to have a THETA angle, or ROTATION angle published with it, to orient it to TRUE north, or St...

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Strictly Surveying

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BStrand

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I guess you could use angles turned only and be good to go, but it's kinda nice to be able to glance at a map and quickly get the general orientation of things with respect to cardinal directions. Not every map has to be a super busy ALTA to be useful...

Posted : February 21, 2024 8:33 am

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Basis of Bearings, rides again.

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