IT IS IMPORTANT TO PRESERVE THE RECORD
Compared to most of you, I am relatively new at this. What I don't understand is when I see surveys that are done on grid bearing to the nearest tenth of a second, how is that "walking in the footsteps" of the previous surveyor. I am more of the agreement that holding a record bearing and preserving the deed record is more important than seeing how many significant digits I can fit into my bearing. I do agree to a point, that grid would be a nice thing so that everyone will be on the same bearing base, but what happens when the next new fancy measuring device comes out that produces something better than grid? How about the surveyors that are not yet using GPS for surveying? Why would you change the bearings of a lot plan laid out 200 years ago where the lots are laid out at 90 degree angles -- say N 32 deg E and S 58 deg E. What justice does it do to change the one line to N 31 deg 57' 48.3" E. Wouldn't it be easier to check other bearings for drafting mistakes than change all of them to what the CAD program reads? I do a lot of work near the Mason Dixon line. I have seen numerous surveys that report that line at many different angles. I highly doubt that Mason and Dixon set their stones to within a tenth of a second on that line. Ultimately, the important angles are the interior angles at each corner. So why not keep it simple?
Neil, Record Bearing Does Define A Grid
The argument is over whose grid should be used. We have an infinity of grids, so you best choose the one I want to use.
Paul in PA
> ...They all were mainly done plucking the bearing between pairs of survey markers then in place from the cadastral ether of prior conveyances and just assuming that bearing was correct for all time.
>
LOL!! That is apparently what our state code requires us to do!!
"IC 55-1902. Definitions. As used in this chapter:
(1) "Basis of bearing" means the bearing in degrees, minutes and seconds, or equivalent, of a line between two (2) monuments or corners which serves as the reference bearing for all other lines on the survey."
Engineers playing surveyor ..... ya gotta luv em'
Basic Facts: The Sun Don't Shine Every Day, ...
...the stars are not clear every night, the skyview is not clear every where and survey budgets are not unlimited.
Paul in PA
Neil, Record Bearing Does Define A Grid
I guess I am getting confused over terms. I am defining "record bearing" probably as most would refer to "deed bearing". I consider it a record bearing, because it is the "record" bearing of that line until another survey supercedes it.
BLM True North Surveys?
Many of the monuments are not out there. They were just computed, (1994 BLM)
N
Correct Neil, But Kent Wants You On His Defined Bearing
He does not want to transform it himself.
Paul in PA
Correct Neil, But Kent Wants You On His Defined Bearing
Not really. If you consider ALL monuments from prev survey are gone... and one is sort of gone...partially disturbed, then the value of an objective BOB becomes apparent.
N
Correct Neil, But Kent Wants You On His Defined Bearing
I find monuments just about everywhere. For example, many of the villages I work in were laid out in the coal mining era. The lots were laid out from the houses. Shoot the corners of the existing houses (original ones) and voila!! you have a bearing monument. Split the houses to hit the party wall and tada!!! your line going the other direction. Now I know they are not all that easy. Pins grow legs and move, houses do not. On many city jobs, the roads themselves can be used as monuments. Many times a road is used for a bearing base. I guess it just depends on what is used on each job. I can see the point for a standardized bearing base, but if everyone can't get to it, then what good will it do? My preference has always been holding the deed bearings when possible.
For those that have an HP41 CX, you can program a button to freeze the time display. I set the 41 using a Timekube before going out. Lead the sun just a hair and when the sun touches the crosshair hit the button on the 41 freezing the time display. I have been doing this since 1990. Other HP calculator may do it also, I have never tried.
James
IT IS IMPORTANT TO PRESERVE THE RECORD
> What I don't understand is when I see surveys that are done on grid bearing to the nearest tenth of a second, how is that "walking in the footsteps" of the previous surveyor.
Well, the footsteps of the surveyor usually refers to the question of where lines were actually run and corners made. As long as the boundary whose bearings you report as referring to either true/geodetic North or grid North runs along the lines as originally located, you are in fact following the footsteps of that surveyor. Reciting a modern bearing with an objective bearing basis like grid North is no different than actually reporting what the distance between the corners really is.
> How about the surveyors that are not yet using GPS for surveying?
For years before I bought GPS equipment, I made solar observations for astronomic/true azimuth, corrected them to geodetic azimuths and from that result computed the grid bearing of the line. The results were typically accurate within a few seconds or less. All it took was a theodolite, a sun filter, a digital stopwatch, and a source for UTC.
Neil, Record Bearing Does Define A Grid
> I guess I am getting confused over terms. I am defining "record bearing" probably as most would refer to "deed bearing". I consider it a record bearing, because it is the "record" bearing of that line until another survey supercedes it.
To me, the "record bearing" is the deed bearing or the original bearing call. It is the "record" of what created the boundary in the first place. Your as-measured is what you field-measured, and it might have a different bearing basis, such as based on a solar observationm, and relative to astronomic north or based on a GPS'd grid bearing based on the state plane coordinates; or something else.
IT IS IMPORTANT TO PRESERVE THE RECORD
What I am getting at is a bearing change of 30 seconds will change a 200' line by 0.03'. You could take the same shot on the same pin 10 times and be off 0.03' for a good bit of the measurements. And I am talking 30". Whatever happened to only report significant digits to a known accuracy? That is where I think part of the problem is and with the public perception of surveyors. If 10 surveyors measure a line, you will get 10 different answers. Why not round to the minute and have 10 answers that agree wtih each other within the tolerances of the measuring equipment and therefore giving the public the perception that we know what the heck we are doing rather than just reporting the numbers that our fancy equipment spits out.
IT IS IMPORTANT TO PRESERVE THE RECORD
> What I am getting at is a bearing change of 30 seconds will change a 200' line by 0.03'.
Well, since an assumed bearing basis that is defined as the line between two monuments disappears as the monuments do. Ultimately you're left with a much, much larger uncertainty than even 30 seconds of arc when the monuments are gone.
That definitely isn't the case if the surveyor did his or her job and reported the bearings of lines in a way that can be reestablished when the monuments are no longer in place.
> I get time from the handheld GPS too.
I'll bite, how do you get dUT, the correction from UTC to UT1? I assume you look that up on the internet since it isn't provided by the time display on a GPS receiver as it is on the broadcast time signal.
> Even more practical and/or feasible is to locate your cursor on Google Earth, I would think, to come up with a latitude and longitude of the observation.
As long as you've got latitudes and longitudes that are accurate within about 80 ft., you're fine both for reducing the observation and for converting near-geodetic azimuth to grid azimuth of the Texas Coordinate System of 1983.
In the old days before handheld GPS, it was easiest to put a station for azimuth obervations near a feature on a quad sheet that could be readily identified and scaled like a point on a road or fence intersection.
You can call WWV to get the ticks or NIST publishes the corrections on-line.
Bear in mind the phone version has a lag so it may not be sufficiently accurate, especially if you are using a cellphone because the lag can be almost a second.
Come to think of it, the time displayed on a GPS receiver may not be very accurate either.
In a nearby county, we have a surveyor who has used astronomic observations for years. He has recently been using GPS and comparing earlier bearings with static GPS derived bearings. He is finding that after applying adjustments from grid to astronomic he is hitting within seconds of his previous work.
That really tickles his fancy and shows just how well surveys could have been placed on a repeatable bearing basis for decades.
Back in school, it seems I recall being able to get very good results for a solar observation in a matter of 15 minutes or so.
> In the old days before handheld GPS, it was easiest to put a station for azimuth obervations near a feature on a quad sheet that could be readily identified and scaled like a point on a road or fence intersection.
Kent, yes, you're correct. That's the way I learned to obtain latitude and longitude for observations and completed many that way.
Google Earth, or my All Topo Maps program has made that chore much easier.
How much latency is there when someone observses (sic) the crosshairs and yells "mark!".
A lot more than if the observer simply pushes the lap button on the stopwatch themselves.
