Caltrans LS and LSIT video and workbook question explanation
I've gone through the very useful Caltrans material here, http://www.dot.ca.gov/landsurveys/workbook.html and have a question about a specific question in the PLSS section. Can someone explain the reasoning of this question to me? I can't neatly include the content of the question here since it is rather involved and multi-part. You'll have to look at the PDF.
It is question I on page 21 of this PDF, http://www.dot.ca.gov/landsurveys/docs/lsit-workbook/12.pdf pertaining to determining the east 1/4 corner (of section 6) from a witness corner (that is on line). I sort of liked answer 3 which is the "single proportion along the line" answer. On page 25, the answer is listed as 4, "none of the above." That also rejects answer 1 which is the "record measurement back from the WC" answer for if it were a specific measurement more like a bearing tree than something on line. An answer which is not included in the "record measurement of 40 ch from the SE section corner" answer. What is the correct approach to this question? When using that approach, what coordinates do you get?
Best regards, Eli
The only reason I can think of is a WC is not necessarily on-line so there is insufficient information given to calculate the coordinate of the quarter section corner. Therefore under this reasoning none of the above is correct.
The 1973 Manual indicates that proportioning would be correct if the WC is on-line but it adds that each case is different, see the notes.
A point on line is called a WP (witness point).
I'd be cautious about blindly accepting an answer to a question that appears to have been on the 1988 LS exam. There are differences between the 1973 Manual and 2009 Manual. I suggest you look at Secs. 6-23 "Witness Corners" and 7-35 "Section Boundaries" in the 2009 Manual as guidance.
For this problem:
1) is 1.07 ch. south of the witness corner on a line between the witness corner and the SE Cor. of Sec. 6
2) is to mistakenly accept the witness corner as now monumenting the E1/4 Cor.
3) is 1.08 ch. south of the witness corner on a line between the witness corner and the SE Cor. of Sec. 6
4) is something else.
If you determine that the proper proportionate method is to single proportion between the witness corner and the SE Cor. of Sec. 6 then the record dimension between the two is 41.09 ch. and the measured is 41.454 ch., which would place the E1/4 Cor. 1.10 ch from the WC.
Or should you single proportion between the WC and the CC corner in which the record is 33.60 ch. and the measured is 33.055 ch., which would place the E1/4 Cor. 1.072 ch. from the WC? Then all you need to decide is whether the E1/4 Cor. should be on the extension of the line between the CC and WC or on the line between the WC and the SE Cor. of Sec. 6.
ETA: One last question: Should the measured distance be from the WC to the CC or from the WC to the line between the two standard corners on the township line? If so, don't forget it's curved! 😀
It's an interior corner so should be a double proportion. Points 11 and 8, and point 7 and ....... nothing to go with it. Go back to the field and find more evidence.
This test in unfortunate in that it encourages the kind of assumptions that get surveyors into trouble every day. You have to assume that the original survey was done by the standard method and was reported to be perfectly cardinal. Never attempt something like this without the original plat and the original notes.
The Manual's primary methods to replace lost corners are only applicable when the prescribed methods were followed. They often weren't. The manual allows deviations due to particular circumstances and by the Chief Cadastral Surveyor's directions, not to mention all the short cuts taken by the contract surveyors.
I recently had a discussion with a surveyor who presented good evidence that the e-w 1/4s were stubbed out, but then he used double proportion to reset a lost section corner. The Manual is not an excuse to not use your critical thinking skills.