Yep, in my world, I am much more worried about why I am measuring 177.23' between monuments that should be 175' apart than I am about a precise geodetic bearing between monuments that I am missing by 2 degrees. 😉
> 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.
However, how difficult should it be for a surveyor to describe the "North" to which the bearings shown on his or her map refer? This should not require breaking a sweat, right? I'll grant you that the upper bound value of positional uncertainty is for extra credit, but as more and more surveyors use least squares survey adjustments, even estimating the uncertainties of points positioned shouldn't require anything more than just scanning the list of their standard errors to see what value none exceed.
The beneficiaries of the basis of bearings note are:
(1) future surveyors trying to follow the footsteps as those footsteps get erased and
(2) mappers trying to show the parcel boundaries in some GIS as well as possible.
It is great that you are working to clean things up and make it more usable... but
If It Ain't Broke Don't Fix It!
You asked, so here is my take on the subject:
First: I think a "Basis of Bearings" statement is both out dated and unnecessary. It had a place in historical times, but not today.
Back in a time in history it was necessary for the use of magnetic compass or solar observations: to find a point on the survey and follow in the foot steps...
I believe what you really want is "Durable Monuments" that can be found and the lines retraced.
Back in the day when I did a lot of control work for design and construction (and had no direct requirement for a "basis of bearings" statement) I made a "basis of coordinates" statement on the control diagram.
In that statement I would describe what control monuments were found/used, their coordinates and other meta data, their published origin, and a few redundant mathematical ties to the lines/monuments/whatever for others to follow. I was adamant that my control diagram was part of the design package, or at least freely available to all.
I seldom staked out those designs. I hardly ever had any questions from the people who did... and it was usually only a "how you doin these days?" type of call.
Until our profession understands why they shouldn't be "pin-cushioning" and setting new monuments because they can measure more accurately than the last guy this item will remain near the bottom of the list of things that need to be considered.
This may be an issue for academia and geodetic surveyors, but few of them conduct boundary surveys in the area I work in.
Also agree. The bearing is down there below intent, natural monuments, artificial monuments, etc. depending on your local law/legislation/statutes/code. I would be more interested in knowing the two sigma confidence of your bearing in relation to the other observed ground monuments than what absolute basis your bearing has. Even a stopped clock is right twice a day.
Well Peter and et al plus the Sacred Bovine herd,
Should not a critical step in boundary analysis and following the 'footsteps' would be to establish durable bearings.
I agree the current client does not have a concern about grid, geodetic, spc, long numbers but we are supposed to provide info. I charge to provide information.
When I review a final plat with clients, I usually point out that the basis of bearing info is not a concern to them but it is stated for the reasons that Kent stated especially his #1. Some clients do maintain a GIS and that is a benefit to them. Unless, you want to take calls from their GISers down the road.
I want my work to be retraceable decades from now.
When their is a conflict in 2050, someone will know what has happened in 2013.
I would assume by this time that 90% of surveyors are using GPS. Establishing a geodetic bearing is fundamental.
I have seem plats here from 20-30 years ago, where some surveyors did not bother to establish any kind of reliable bearing basis. I have seen where they used a 'record' bearing off a 19th century GLO plat bearing. I have also seen where others were earnest in establishing solar bearings.
I am all for durable monuments but I really want to know the bearing that is true.
Like I said, it is one of the most important steps in finding past work that may have had problems when the monuments are gone or suspicious in nature..
Peter, I always enjoy and find myself on the same page as you. But this time, I gently disagree.. You sort of contradict yourself. "If it isn't broke that don't fix it" Back then technology was magnetic with deviation for informational purposes. Today, the technology needs a little more elaboration.
my state is something like 85% forested. When surveyors in my area hear the phrase "State Plane" they look up.
Perhaps... Perhaps...
Perhaps, Mr. Burkholder is off track in proposing a mandatory bearing relation to something more reproducible than what is current common practice. Some have suggested it is wrong to attempt to legislate this. I appreciate their perspective. I am continually shocked, however at those of you that give such puny reasoning against using geodetic/astronomic (and SPC grid would fall under either of those). Excuses such as expense, the time needed on a small job, the trees, the client's needs, a competitor's incompetent performance (pin cushioning) and the knowledge base required to derive said bearings are all hurdles to be sure, but none of them should ever interfere with a professional providing a professional product. It could be argued whether a Geodetic/Astronomic bearing relation is a defining attribute of what a professional product is or is not. That's fine. It's a discussion worth having. But arguments based on knowledge required, expense, and working environment, makes YOUR PROFESSION look very very small.
We put solid bearings, related to a defined meridian, on almost all of our work because it benefits the public for future generations. Our clients today don't really know the difference or care for the most part whether we take off from a specious deed bearing or a GPS derived bearing, a sunshot or a compass bearing. However, each time I repeat the procedure of plotting multiple descriptions together on a new job just prior to field reconnaissance, and then immediately start navigating to called for monuments within minutes of stepping on the ground after locating only one monument because one of those descriptions referenced a Geodetic/Astronomic bearing, it becomes very clear that reproducible bearings (and ultimately georeferencing cadastral work) benefits the public by making boundaries more easily recoverable. This is a benefit that will extend out for years.
Furthermore, twelve plus years we've been tying our work to the NSRS (National Spatial Reference System). Some local crackers are still putting out crappy work. But more and more, we and others like us, are filling in the cadastre with surveys that fit together very very well. Just because (*I really want to put a name here*) can't find the right monuments nor measure the right distance between them doesn't mean we won't forge ahead with a continual desire to provide an increasingly more excellent product. We will not let our work be defined by the least common denominator. If that makes me and others like me an "egghead" so be it. However, be reminded, just because these "eggheads" are taking the necessary steps to provide better documentation to their work doesn't mean they aren't also doing the requisite level of research and digging to find the right monuments. It's not an either/or proposition. In fact, you can provide a real bearing between the real monuments. You don't have to choose between determining real bearings and finding the monuments. Do both.
> I want my work to be retraceable decades from now.
>
> When their is a conflict in 2050, someone will know what has happened in 2013.
Yeah, I take it for granted that modern life will continue to destroy the most durable monuments with a vengeance and that eventually some surveyor will be left with either a very good record to use in restoring the tatters of some boundary or a very poor record that will mostly be unhelpful. I don't plan to be in the latter category if I can help it.
It frankly surprises me quite a bit that most surveyors have not recognized from experience how much more easily things fall into place if you know quite accurately the actual direction of "North" to which the survey you're working with refers. Costs very little and is a vast improvement in quality.
I don't think anyone is saying that a dependable, accurate, and reproducible basis of bearing shouldn't be used by all of us performing boundary surveys. What many of us are saying is that political bodies requiring it and defining it for our profession is not indicative of a profession at all. If we are going to require (and we should) an adequate basis of bearing on every record of survey, it should be our profession requiring and defining what is adequate. Heck, we still have many states allowing stealth surveys (no method of recording), yet here we are arguing about what basis of bearing is adequate. What the heck good is a reproducible, dependable and accurate basis of bearing if the information is kept secret?
We have bigger fish to fry as a profession than worrying about what words should be included in a regulation/law concerning a basis of bearing statement. We still have many licensing boards full of engineers and other non-professionals drafting, interpreting and enforcing the laws and standards of our profession. Maybe it is time we decide, by our actions, whether or not we are going to be professionals or technicians. If we choose the former, maybe we ought to start acting like it, and earn the respect we desire.
Perhaps... Perhaps...
Shawn, your standard procedures are obviously serving you well. A person could learn a lot by following your lead, so to speak.
I have two questions for you. When you put a solid bearing on one of your surveys do you go off the deep end in a fashion like Mr. Burkholder proposes? And,why don’t you put a solid bearing on all of your surveys if it is so easily done?
OK I will read it a few more times. It's a grand idea. I just start to tune out at the words "global" and "should".
> A rather elegant proposal. I like it more each time I read it over.
Except doesn't it fail to accommodate a modern solution such as the various projections of the SPCS for a particular state or some other standard projection?
I suppose in theory one could state that the basis of bearings is geodetic North determined at some point a hundred miles away on the central meridian of a Lambert projection, but isn't that a bizarre and unnecessarily complicated alternative to just mentioning the actual projection?
It definitely needs to be better than the rather-too-common "Easterly line of tract is assumed North". That might as well be left off because it tells us nothing more than "This plat gives no clues about absolute bearings".
If I were writing a regulation, I would say that all plats must give some measured absolute bearing and explain how it was obtained. Leave it to the professional to decide how to do it - compass corrected for declination, GPS vector converted to SPC grid at point X, or whatever the profession considers adequate practice for the situation.
It has always bugged me that the practice of giving bearings on each line started when everything was done by compass and actual bearings were measured, but when the practice switched to measuring angles the plats still had line bearings. Wouldn't it make more sense to record what was measured? From an error propagation point of view, knowing what angles and distances were measured tells you more.
Perhaps... Perhaps...
> I have two questions for you. When you put a solid bearing on one of your surveys do you go off the deep end in a fashion like Mr. Burkholder proposes? And,why don’t you put a solid bearing on all of your surveys if it is so easily done?
To your first question: our efforts are in a constant state of evolution. So you'd see some small, slow changes to how we have documented our bearing relation over the years. Presently I think it is best to document how a Geodetic/Astronomic bearing was determined (GPS, Solar observation, Polaris observation, etc.). That will give some indication as to the likely expected accuracy. I also think it is good to give the Lat/Long of the origin point for those observations. That isn't necessarily where the bearings were determined. Giving the origin is useful for determining the convergence. The origin doesn't need to be terribly precise either. The exception to this would be bearings based on some projection like State Plane or UTM with constants that are readily available.
To your second question: I try to be as honest and unambiguous as possible in my conversations with people. I'd be lying if I said I put Geodetic bearings on all of our work. Construction layout doesn't require it in many cases. In well monumented subdivisions with small lots, Geodetic bearings probably don't serve much use. I stress the "probably" because my imagination is limited. Perhaps there's some benefit I don't see. However, in a well monumented subdivision (and I can't stress the well monumented part enough), the reproducibility is in the surrounding lot/block monumentation and the street lines (centerlines or curb lines). However, when performing lot surveys in subdivisions that are not well monumented (monument types vary, no bearings are listed on the plat, streets are rough asphalt with ditch-to-drain) we do the necessary work to place them on a Geodetic bearing.
Perhaps... Perhaps...
Surveyors in some states get to enter on to nearby properties to complete a survey. In the remaining states, surveyors have some credibility that will often convince neighboring land owners to allow them on the property. But there are non-surveyors who need to use a basis of bearings to locate overgrown monuments when only one monument can be found. Such non-surveyors include the owner, builders, and fence contractors. So the basis of bearing should be stated in a way that can be reconstructed without leaving the property that is the subject of the survey. For just relocating an overgrown monument that isn't too far away, it probably suffices to make clear if the basis of bearing is magnetic, or truish (that is, geodetic, grid, or astronomic), or if it is based on an assumed bearing. Obviously an assumed bearing isn't very useful to the owner unless he's on really good terms with his neighbors.
Earl: I like being able to reference it to a known entity as you have described. Where I live in PA there is usually no basis of bearing at all, and frequently adjacent tracts do not use the same (probably magnetic bearings at different times not corrected for declination).
However, I would not exclude the possibility of referencing it to a grid system like SPC or UTM (which are, in turn, referenced to geodetic north at a particular meridian probably a large distance away). Or even a local grid, for example the City of Pittsburgh has a grid system with a central meridian at 80°00'00.0" (referenced to NAD, the predecessor to NAD27).
One thing some of the posters need to realize is that the convergence angle changes very slowly (delta longitude times the sin of latitude, on a sphere). So, at 40° latitude, one would have to go about 0.8 miles east or west to make a difference of 30". So whether it is NAD27, or NAD83 (86), or NAD83 (2007) or NAD83 (2011) or WGS84, the geodetic bearing of a line is really the same (excluding an azimuth bias that might be present in, for example, NAD27, but that would still be in the 1-2" range).
The Basis of Bearings if used can be of little value unless one line is designated as such and every other bearing based on that on that one designated line. Really does not matter what that line is based on, could be assumed, magnetic or about anything as far as the survey is concerned. The need of recovery and stability of that base line is legit but in my experience even if that line is recovered intact, later work will seldom match the record relationships exactly, but the new ties are usually within reason and therefor are considered to be following in the footsteps. I have never found a description describing a tract of land with less than 3 sides, that quirk of geometry provides 3 chances to recover the Bearing Base, IE "Base Line". On a regular basis we use record and other evidence to retrace the location of Boundary Lines so doing so to recover a Base Line, one of the property lines, within reason should not be above out ability's. I like seeing a line designated as a Basis of Bearing on Records of Surveys and Plats, matters little to me what the bearing shown for that line is intended to represent, other than its relationship to the rest of the data shown.
jud
I sure agree with you Bear. People new to GPS and using geodetic north are sometimes shocked to see than the reverse course of an approximate east-west line is not equal to the original course plus 180 degrees. This mess can all be taken too far.
Proposed Basis-of-Bearing - Followup
Thanks to everyone who took the time to contemplate and respond. I sincerely appreciate your input. As it stands now, I plan to:
1. Download the entire thread to "onenote" on my computer. Doing that, I can browse the entire thread off-line.
2. There was a thread (on using assumed bearings) back at the end of December 2012 and beginning of January 2013 that provided food for thought as well.
3. Scott and I will attempt to glean from both threads and summarize. Look for an additional post in a week or two.
Thanks again and keep stirring the pot. . . that is how we learn from each other.
