Proposed Basis-of-Bearing

I love a good solid reproducible bearing reference. I like where you are going, I'd only have two caveats:

For giving the point where the azimuth was based, I'd leave it flexible enough to simply provide the Lat Long and not require the point be graphically shown. I've been in the practice of using custom projections that might have an origin that is not within the map area.

Second, I'd give some consideration to an accuracy statement. Bearing precision will be somewhat dependent on line lengths. If the longest line is only a couple of hundred feet in length, 30 arc seconds could be in the centering of the monuments.

Good stuff though.

I wonder about the phrase "physically defined". In practice, geodetic latitude and longitude are based on adopted latitude and longitude of a set of stations, such as those in the International Terrestrial Reference Frame. The actual latitude and longitude at any moment of time will actually be different due to polar motion. So is "physically defined" a good phrase for a human convention that has a bit of arbitrariness to it?

Then there is the mention of the possibility of higher-order surveys, but no corresponding requirement to state the parameters of the geodetic system adopted.

Okay, I read your proposed "standard" statement. While I recognize that you have your global coordinate basis, and that you probably have a higher-level knowledge on coordinates I have some issues with requiring a too precise set of rules on bases of bearings.

If I am reading your "standard" correctly, I would want to ask about the small surveyor who might come out to do a small lot survey and replace a couple of property corners. S/He should be allowed to utilize a couple of found monuments, and use the platted bearing between those monuments to serve as a bearing base on his drawing. He should not be expected to have to establish a new bearing base just to serve a new standard in the law that does not accommodate him or his client, but only costs them more money.

And what about another scenario where a client might want a lot of points with state plane coordinates on them and they whole basis of bearings is simply on a state-plane bearing base.

Also, do you have to have one point around which all the bearings are based? If you do a GPS static survey using all the points you have out there, maybe your bearings are based on the actual coordinates you are publishing. All the points are your basis of bearings. Why limit your statement ot one or two of those points?

I see trying to micromanage many standards in surveying limits the surveyor and the surveyor's particular needs in a specific type of survey. We often rearrange how we do things because a law is out there trying to stop a specific pet peeve or problem that has occurred in the past, but ends up causing more problems than it is attempting to correct.

I just copied and pasted your proposed standards below. I hope I did not misinterpret what you are trying to accomplish.

> The basis-of-bearing on this plat is true north with respect to the longitudinal meridian through “a point identified and shown on the plat.”

The basis-of-bearing on this plat is true or astronomic (circle one) north with respect to “a point identified and shown on the plat” and is accurate within _____ arc seconds at the 95% (two sigma) level of confidence.” For purposes of this survey, true north and geodetic north are synonymous.

On most surveys, is not the use of bearings generally just a means of expressing the angle between two lines? Is whether or not the bearing basis is true north, or grid north, or magnetic north really that important on most residential surveys. When doing a boundary survey, most times you are occupying your control stations and locating evidence radially from those stations, so your bearing basis may have been based on angles from two control points that may or may not have been established by GPS, or ties to an existing control network....

Guess I am a little concerned that we may be getting carried away with concerns that have too many variables to control.

:good:

Well put.

Professional Autonomy

Definition: The quality or state of being independent and self-directing, especially in making decisions, enabling professionals to exercise judgment as they see fit during the performance of their jobs.

Agree

James has it!!

Why does the surveying profession have this uncontrollable need to legislate and/or regulate the smallest of details of our profession? Are there laws in place that define how an engineer is to use stationing, the size of sheet a headgate design must be drawn on, a north arrow, etc.? Does the medical profession have laws that specifiy the size of a prescription pad?

Why do we allow this to happen to our profession? Do we really need this level of hand-holding? Please leave it alone, but if you must define the requirement of a basis of bearing please only include your first sentence: "When submitted for recording or review by an approving body, the basis-of-bearing should be shown on each survey plat for the purpose of establishing a common reference and for the convenience of subsequent users." Nothing more is needed.

With just a once read through it seems this definition of Basis of Bearing is different form how we established basis of bearing for boundary work. I have always been under the impression that the entire point of Basis of Bearing was to have two points to establish the direction of North. I can get a different north using astro, historical government control Monumentation, current gov. control Monumentation and GPS depending on what epoc used.
So how can you get basis of bearing from one point?
Doesn’t “North” move according to just about every different way it is defined, and isn’t that why Basis of Bearing is so useful for retracing and resetting corners by plat angle?
From my perspective a major purpose of a plat is to show best evidence to a following surveyor so he/she can reestablish the corners on the ground as they were set for the plat.
Including a basis of bearing from two solid field reference points that are within or very close to the property being surveyed is by far the most useful info for me to successfully retrace the plat. I even believe they should be on a record line and be able to be directly tied (inter-visible) rather than have multiple setups (angles).
I have had several conversations with surveyors private, state and blm and it is surprising how many have a different idea of what true bearing or even - bearings based on true north, means on any particular plat.
Non-magnetic- any source as long as it’s not compass
True north – one true basis and then angularly correct but grid, not true from any point except the basis
Geodetic – true north on every point toward and away or mean
Based on - GPS when, it changes regularly
ground control - state, federal, local,
astro, etc

If I see a basis of bearing from GPS or some blanket statement like North based on NAD83, I rarely make the effort to recreate because it is too variable in definition.
Likewise I believe basis of coordinates can only be useful if its from a point on the ground I can actually survey.
I do believe it is a big help and should be required for plats

Out of academia comes the need to have one solution and never to have it questioned. This is just another step along the road through the perfect world of taking the control of boundary surveying and all other types of surveying from the field into the office where all can be made perfect. If and when it gets accomplished, crews will be sent into the field with the proper solution to set monuments where computed, with no interest of the quaint attempts of surveying or boundary's that were established before. The system would work well after several hundred years of implication, except as we get better at measurement we will find more and differing rates of movement on this live planet we live on. SPC, GIS and Low Distortion Projections, should be easy to see the trend and the source. Are we outsmarting ourselves? Knowledge and the ability's allowed from technology without the application of wisdom can cause harm for those who follow. Well informed without the application of wisdom, attempting to control and change the methods that years of study and experience have established, is not progress.
jud

> I've worked with the local city surveyor to come up with a simple, concise, rigorous statement for basis-of-bearing. See http://www.globalcogo.com/Basis-of-bearing.pdf
>

Increased regulations might protect the public. But they generally have two unintended consequences (at least):
1. They are a barrier to entry of new competition, and they are a barrier to the "little guy".

2. People that don't understand or are unable or too lazy will make up something, fake it, etc., and the public is left expecting a protection it does not receive.

>Feedback is solicited from any/all interested parties having constructive comments.

You didn't include the precision required for the lat/long? Or did I miss it?

If I read this right, you could work real hard, or you could ask your cell phone for your location and pull out your $25 compass and you're good to go?

Also, if you go this far, why not include or limit the requirement to SPC coordinate and bearing based on either existing published mons or on CORS. This provides real, long term, reproducible distances and angles.

Seems like absolute extreme academia overkill...

:good:

It seems to me that your convergence equations are incongruous with your sketch and explanation.

While I believe that each survey should either be based upon or related to a well-fixed basis of bearings, the convenience of subsequent users is hardly a valid reason for going to such lengths on an ordinary survey, as the effort is disproportionate to the value it adds to that particular client.

I think that the much smarter, and actually more professional, approach would be to define what the desired PERFORMANCES of the note are. What I would want to see include the following:

(1) How the "North" direction to which the bearings shown on the plat refer was determined, i.e. by (a) assuming the bearing of some monumented line as reported in a referenced instrument in the public records, (b) astronomic North determined by some stated method of astronomic observation, (c) geodetic North determined by some stated method of observation, (d) grid North of the stated zone of the SPCS as determined by stated method, or (e) by crowdsourcing, averaging the estimates of the direction of line posted to BeerLeg.com.

(2) at what point upon the ground the reference "North" refers (not relevant for grid North of the SPCS since it does not require that information in the way that record North, astro North, and geodetic North do,

(3) how that reference "North" was transferred throughout the project, i.e. by RTK roulette, conventional traverse supplemented with static GPS vectors, or whatever, and

(4) some number representing the best estimate of the upper bound of the local uncertainties of the coordinate positions from which the bearings and distances shown on the map were computed.

Example of the last:

>"Coordinates are in units of US Survey Feet and refer to the Texas Coordinate System of 1983 (Central Zone); NAD83 (2011) Epoch 2010.0 as derived from connections to the National CORS network via six one-hour sessions of L1/L2 GPS observations logged on two different days and processed using the National Geodetic Survey’s OPUS-RS utility. The coordinates in the following list were obtained by a combination of GPS and conventional methods and are estimated from analysis of variance to have standard errors in N and E components of less than +/-0.01 ft."

Having a statement of the uncertainties in the bearings at the point of origin is not really very informative if what one really wants to know is what the upper-bound uncertainties in all of the lines shown on the map are. Those will, of course, vary throughout the survey with the design of the network.

You'd want the boobs who are putting notes on maps to the effect that bearings refer to "GPS North" to continue to do that so that posterity will know their work was all a massive clusterfuge, I'd think. It's basically a Truth in Labeling issue.

> You'd want the boobs who are putting notes on maps to the effect that bearings refer to "GPS North" to continue to do that so that posterity will know their work was all a massive clusterfuge, I'd think. It's basically a Truth in Labeling issue.

:good:

I truly do not enjoy hurting anyone's feelings, BUT, there is a huge difference between technical extremism and gettin' the job done. Application of the "deep thinking" definition of the basis of bearings on a survey plat is of absolutely no use to anyone except another egghead. Those of us who actually recover existing monuments and other evidence relevant to our project know that it is impossible to get two surveys of the same monuments to agree to the same level of "correctness" as dreamed of in Mr. Burkholder's world, especially as the time between the two surveys grows. As practioners, we are most concerned with finding the physical monuments left behind by the first surveyor. "Computational monuments" are not worth much out in the real world.

> I truly do not enjoy hurting anyone's feelings, BUT, there is a huge difference between technical extremism and gettin' the job done. Application of the "deep thinking" definition of the basis of bearings on a survey plat is of absolutely no use to anyone except another egghead. Those of us who actually recover existing monuments and other evidence relevant to our project know that it is impossible to get two surveys of the same monuments to agree to the same level of "correctness" as dreamed of in Mr. Burkholder's world, especially as the time between the two surveys grows. As practioners, we are most concerned with finding the physical monuments left behind by the first surveyor. "Computational monuments" are not worth much out in the real world.

:good: Just what I was thinking, but did not know how to say it.