Curb Splits and Basis of Bearings

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kwilson
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Curb Splits and Basis of Bearings

Postby kwilson » Tue Jul 23, 2019 9:53 am

When determining a block with curb splits have you ever used the centerline derived from the curb lines as your basis of bearings per the original map? Does this comply with 8764 (b)?

A good practice in this situation is to provide reference monuments in appropriate places around the block so that future surveyors can retrace your boundary determination. Likely they will check the curbs and accept your solution. Having definite tagged reference points to precisely re-create your survey will help subsequent surveyors to be able to accept and agree precisely with your determination.

What is the definition of a Basis of Bearings?

Can a basis of bearings be a calculated line between two determined points where no actual physical monuments exist?
EXAMPLE: Using RM's to establish the location of a USCGS control point and then using that location as one end of your basis of bearings.

Ken Wilson
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Dave Lindell
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Re: Curb Splits and Basis of Bearings

Postby Dave Lindell » Tue Jul 23, 2019 1:30 pm

I have always used "a monumented line of record" for a basis of bearings when checking maps.

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LS_8750
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Re: Curb Splits and Basis of Bearings

Postby LS_8750 » Tue Jul 23, 2019 2:50 pm

In the Santa Cruz Mountains, I've run across "solar observation" being the basis of bearings on maps several times.
I've seen curb splits and record bearings from old subdivision maps used in Sacramento.

For what it's worth.

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btaylor
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Re: Curb Splits and Basis of Bearings

Postby btaylor » Tue Jul 23, 2019 3:42 pm

Curb splits are totally fine with me for BOB. As mentioned, solar observation is fine too. I think the real issue is most definitely retraceability.

Someone can do a nice, closed loop traverse around the block, splitting curbs, and set a single property corner on a lot in the middle of a block. I can't rely on the map any more than knowing I would need to split curbs as if there was no prior survey. As long as the person sets RPs at the intersections that allows me to get onto the survey then to me it's all good. I'd shoot some curbs to check but I wouldn't go nuts resolving everything again.

I dont see how 8764(b) clarifies the concept of how the BOB is established. I just see it as requiring a BOB in the first place.

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mpallamary
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Re: Curb Splits and Basis of Bearings

Postby mpallamary » Tue Jul 23, 2019 6:28 pm

I used to do solar bearings all the time. It was always fun and interesting. Most early maps were based on a solar.

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PLS7393
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Re: Curb Splits and Basis of Bearings

Postby PLS7393 » Thu Jul 25, 2019 6:14 am

Curb splits are sometimes the best evidence of the original monuments/mapping. I have used curb splits and found original points to support my B.O.B.
The Board has no issues using curb splits as a B.O.B., but now days we have to do a record of survey showing our work.
Keith Nofield, Professional Land Surveying
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MikeT
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Re: Curb Splits and Basis of Bearings

Postby MikeT » Wed Jul 31, 2019 11:14 am

I agree with Bryan on this. If you have enough monuments shown to retrace the survey, then what's the problem?
I don't agree with monumenting a split curb BOB because a lot of the time those spikes or 3" nails and washers or whatever is
set will get paved over or wiped out. And most small shop surveyors don't have it in their budgets to put street monuments in
for a simple lot survey.

I know there has been a reliance on the CEAC guide for this issue, but it appears there hasn't been a set standard for
this practice.

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Jim Frame
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Re: Curb Splits and Basis of Bearings

Postby Jim Frame » Wed Jul 31, 2019 2:44 pm

I don't agree with monumenting a split curb BOB because a lot of the time those spikes or 3" nails and washers or whatever is
set will get paved over or wiped out. And most small shop surveyors don't have it in their budgets to put street monuments in
for a simple lot survey.


Monuments don't have to occupy the street centerlines, they can be set anywhere convenient and referenced to the centerline or block line intersections by bearing and distance on the ROS. I usually set them in the curb or sidewalk. It's quick and easy, and leaves a solid point for retracement.
Jim Frame
Frame Surveying & Mapping
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Davis, CA 95616
[url]framesurveying.com[/url]

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btaylor
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Re: Curb Splits and Basis of Bearings

Postby btaylor » Wed Jul 31, 2019 3:41 pm

There has been so much street repaving lately I consider any control in roads to be a lot more temporary than when I was first working in the 90s. I'm pretty shocked if I find control from 10 years ago. Any reference marks are set in concrete away from potential handicap work (or in the area new handicap ramps) whenever possible.

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hellsangle
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Re: Curb Splits and Basis of Bearings

Postby hellsangle » Thu Aug 01, 2019 7:21 am

Speaking of street monuments . . .

I've found cast-iron monuments hand-hole access-covers buried 0.5' under asphalt in Marin County! So nuttin' is safe!

Surveyor-to-Recorder, yep, Crazy Phil - Sonoma

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Re: Curb Splits and Basis of Bearings

Postby Peter Ehlert » Thu Aug 01, 2019 8:50 am

immediately after the Loma Prieta earthquake I did a bunch of work in old town Santa Cruz.
Hand-Hole monuments in the Sidewalks! awesome, more secure, and no traffic hazard.
we did have to time our work to avoid the foot traffic but that was a minor inconvenience compared to dodging cars
Peter Ehlert

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E_Page
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Re: Curb Splits and Basis of Bearings

Postby E_Page » Tue Aug 06, 2019 3:20 pm

The Sacramento PPC reviewed a case involving curb splits about 10 years ago, and as I recall, as both a response comment to the surveyors involved in the case and as general educational info to the chapter, we recommended that when curb splits are relied upon, that the surveyor set centerline intersection or block monuments to memorialize the resultant line.

The reason being that when determining a block line by curb splits, the result can be slightly different depending upon the number of and location of the shots along the curbs used to determine the line. Another reason which came up on one line in the case we were reviewing was that at some point, the city had replaced the curb on one side, slightly widening the street on that side. If a following surveyor doesn't pick up on that info by checking with the local DPW, they would come up with a different location. Unfortunately, too many will simply jump to the conclusion that the previous surveyor was wrong because he was an incompetent measurer or incompetent calculator.

Whatever is used as a basis of bearings, the only two things which are of actual importance is that 1) the survey is accurately related to it, and 2) the surveyor leaves a means of ready and reliable recreation of the basis.
Evan Page, PLS
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Gromatici
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Re: Curb Splits and Basis of Bearings

Postby Gromatici » Thu Aug 08, 2019 12:51 pm

You can put a note on the map that states: "The basis of bearings for this survey is assumed being __degrees __min. __sec for the northwest curb line of line of ____ Street as field located on January, 2019. The bearing used for this averaged curb line was derived from the map filed _________ pages ______ of ______ for the northerly/easterly/westerly/southerly line of ________ Road shown on said Map." Something like that will tell everyone that your just taking the bearing shown on an old map, and apply that to one of the lines of the curbs you surveyed. It's O.k. to have an assumed bearing, we do it all the time when we reference a record line in a map vs. using CCS83, Solar, or Polaris obs. In downtown Santa Barbara, NONE of the older (1853-1883) maps have any bearings. However, every surveyor new that each block was either 41-30 or 48-30, and so many maps assumed that bearing between city block monuments. That was fine, since bearings are really just a way to express the angular difference between lines. The issue comes up with you only have 1 monument in a tract left, and thus having Polaris, the Sun, or CCS83 as a basis is a much better foundation. I would set some center line intersections, around the block so that other surveyors will use them and work off of them, and not reject any on-site monument that are more likely to get disturbed.

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mpallamary
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Re: Curb Splits and Basis of Bearings

Postby mpallamary » Thu Aug 08, 2019 1:11 pm

I started my career in New England in 1971. We did a lot of ancient surveys, retracing descriptions and deeds from the 1600's. Don Wilson and I have discussed this numerous times. Back when these deeds were created, they were based on magnetic bearings. Over the years, we had to refer to isogonic projections to figure out where mag was 300 years earlier. New England was heavily wooded and we could not take solars, nor could they back in 1630. Most of the rules of retracement in New England came from Old England.

The one thing we knew and learned was, to make the best effort to figure out where things were. A Magnetic basis of bearings has been good for most of the world since the beginning of measurement. That would be a viable augment to this work. I do like the idea of placing a few reference monuments out there.

Just because we have modern tools of measurement, does not mean the old ones aren't any good.

See the link below.

https://cdn.ymaws.com/www.nysapls.org/r ... -02_HA.pdf

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Olin Edmundson
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Re: Curb Splits and Basis of Bearings

Postby Olin Edmundson » Sat Aug 10, 2019 12:55 pm

I split curbs on any old subdivision in town where you have improvements built near the time of the original survey, and use them for a bearing base all the time. In terms of retracing your survey, there typically isn't a problem if you got enough actual monuments in the block. The curbs, as surveyed, can be re-established through ties to the monuments.

I also have a compass bearing taken on every survey we do, city or country. However, I don't see that publishing this reading on a map would provide any significant value as a compass only reads to a degree or two by a skilled surveyor. As we know, just a degree of error would make close to 9 feet in a typical 500' long block.

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hellsangle
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Re: Curb Splits and Basis of Bearings

Postby hellsangle » Thu Aug 15, 2019 4:09 pm

The issue comes up with you only have 1 monument in a tract left, and thus having Polaris, the Sun, or CCS83 as a basis is a much better foundation.


Gromatici is spot on! With GPS, or Celestial observations, we can (and probably should) place all surveys on Geodetic North. (I've recently revisited an very old survey where a long ago Solar observation compares within seconds of a 2019 GPS observation.)

To reiterate Gromatici - all you need is one point on the survey to reproduce a previous survey based upon True North! (BTW: Interesting discussion regarding basis of bearings ensued at last week's BPELSG presentation in NorCal.)

Crazy Phil-Surveyor-to-Recorder - Sonoma

PS Considering the post-conflagrations/abandonments/infrastructure surveying/LLAs/Subdivision review/etc. . . . the poor County Surveyor has more than enough his/her plate without having to review/police Records of Surveys! They are doing more with less! So, Surveyor to Recorder would most certainly take some of the workload off the County.

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Re: Curb Splits and Basis of Bearings

Postby PLS7393 » Fri Aug 30, 2019 7:17 pm

And to add to your original post and question, I have never been able to locate a good definition of a Basis of Bearings (B.O.B.).
Some counties have an ordinance (or attempt) to require two found mapped points for a B.O.B.
I have no problems using curb splits, since curbs may be the best available evidence. They usually were constructed as improvements with the intent to be parallel to mapped boundaries, unless able to prove otherwise.

Mike T. mentioned being a small shop doesn't allow a budget for setting full on standard monuments (with well), but I have set a "MAG" nail with 1.5" washer stamped "KEITH NOFIELD PLS 7393" to re-establish a monument/offset line. That will allow you all to follow my footsteps.

How many of you have found untagged nails in the pavement at curb splits? I was taught a good curb split is at the returns, and that's where I find many nails that fit. If they fit, I note them on my map and move on.
Keith Nofield, Professional Land Surveying
PLS 7393

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kwilson
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Re: Curb Splits and Basis of Bearings

Postby kwilson » Tue Sep 03, 2019 5:52 am

Thanks Keith and all for your answers. I got the idea to set various tagged control points at the extreme ends of the survey as described by Keith Nofield from maps that Bryan Taylor has filed. I have been able to retrace the locations shown on Bryan's maps using that control.

In many cases many of the property corner monuments that surveyors have set over the years have been destroyed by street improvements and property line improvements (fences, driveways, walls, etc.) so having tagged control monuments of record in the street, curbs or sidewalks provides for more reliable future retracement. Of course any found monuments if they still exist can be used - the more the better.

Regarding which locations are more permanent i don't see a big difference between having nails and tags in the street pavement, on a curb or on a sidewalk. We have all seen how construction often removes and replaces curbs and sidewalks and paves over street monuments. So from what i have just described, I plan on setting more tagged control points and showing their locations on my filed maps. This will help my company and others to retrace the survey more efficiently in the future.

Ken Wilson
LS 5571
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btaylor
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Re: Curb Splits and Basis of Bearings

Postby btaylor » Wed Sep 04, 2019 8:14 am

kwilson wrote:
Regarding which locations are more permanent i don't see a big difference between having nails and tags in the street pavement, on a curb or on a sidewalk. We have all seen how construction often removes and replaces curbs and sidewalks and paves over street monuments. So from what i have just described, I plan on setting more tagged control points and showing their locations on my filed maps. This will help my company and others to retrace the survey more efficiently in the future.




My only quibble with this is that streets are scraped a hell of a lot more than sidewalk. At least here in the Bay Area it can astound me how quickly street reference points are gone when I presume I have a recent ROS to work from.

If the handicap ramp is new with the truncated domes, then it's probably safe to assume you can set reference points on those instead of the road. If the handicap ramp is older and lacks the domes, then I wouldn't expect them to survive at all, and I will try to set them on a curb away from the potential future work to the older ramps.


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