Is this Basis of Bearings Statement adequate?

[Robert Martin]

The Basis of Bearings for this Survey is the California Coordinate System of 1983 (CCS83 (2011) Epoch 2010.00), Zone #, as defined by Section 8801 to 8819 of the California Public Resources Code, Based on NGS Survey Control Monument PID xx####, designation HPGN CA ####. An elevation of #,###.# was used to determine a combined scale factor of 0.999##### with a mapping angle of -0o35’00”, as indicated on the NGS data sheet for said monument. All measured distances shown are GRID, divide distances by the combined scale factor to obtain ground distances.

I came across this statement recently on a Map, I'm couirous what you guys think, Thanks!

[RAM]

to me, the basis of bearings statement should be separate statement from the information required by the PRC. But I am open to ideas

[Warren Smith]

A Basis of Bearings statement is required, and this is consistent with that basis being derived from CCS83 control. It can also be construed as the basis for grid distances shown, and any state plane coordinates derived therefrom.

[Steve Martin]

"Is this Basis of Bearings Statement adequate?"

Maybe. Maybe not.

The Public Resources Code technically allows ties to only one control point.

8813.1. After December 31, 2005, any survey that uses or establishes a CCS83 value or values shall meet all of the following requirements:
(a) The survey shall be referenced to and shall have field-observed statistically independent connections to one or more horizontal reference stations that is or are one of the following:
(1) CSRN station.
(2) Geodetic control station located outside of the State of California that meets all the requirements for inclusion in the CSRN except that the station is outside California.
(3) Existing CCS83 station that:
(A) Is shown on a map filed with the applicable county surveyor by a public officer, subdivision map, corner record, or record of survey.
(B) Meets all the requirements for inclusion in the CSRN, except that the station and its data are not published by NGS or CSRC.
(C) Has an accuracy, conforming to the applicable CSRN requirements, stated for the station's value.
(4) Existing CCS83 station that:
(A) Is shown on a public map or document that is compiled and maintained by the applicable county surveyor.
(B) Meets all the requirements for inclusion in the CSRN, except that the station and its data are not published by NGS or CSRC.
(C) Has an accuracy, conforming to the applicable CSRN requirements, stated for the station's value.
(b) If an accuracy is to be claimed for the CCS83 value or values established, the claimed accuracy shall be an accuracy standard published by FGDC or FGCS.

However there are issues apparently unresolved in that statement. Using only one physical point, technically the basis of bearings would be the broadcast orbits of the satellites used to determine positions relative to that single point. Broadcast orbits are on WGS84 which is very similar to ITRF and there are fundamental differences with the NAD83 datum of the California Coordinate System.

Also there is no mention of correction for the epoch date of the survey to the published epoch date of the control.

CSRC and the League of California Surveying Organization have a sample BOB statement. The attached is from the League website.

[Edward Reading]

Nice Steve, thanks for posting that.
Ed

[Steve Martin]

Attached are a few slide from a seminar I used to give if anyone is interested

[Robert Martin]

Thanks for posting those slides Steve!

[rmaher]

Here is an updated sample provided by the CSRC: http://csrc.ucsd.edu/docs/BasisOfBearings.pdf

-Rich

[Edward Reading]

Thanks Rich.