Community Forums

Share:

Caltrans LS and LSIT video and workbook question explanation  

Page 1 / 3

Protracted
Posts: 33
Member
(@protracted)
20+ posts
Joined: 1 year ago

Hi all,

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

Topic Tags
43 Replies
Dave Karoly
Posts: 10197
Member
(@dave-karoly)
10,000+ posts
Joined: 9 years ago

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).

Reply
Gene Kooper
Posts: 951
Member
(@gene-kooper)
500+ posts
Joined: 4 years ago

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!  😀 

Reply
12 Replies
aliquot
Member
(@aliquot)
Joined: 8 years ago

1,000+ posts
Posts: 1052

The correct way to do this is the same in both manuals.

Where are you getting the 41.09?

You cant single proportion between two points on the same side of the corner you are trying to reestablish. 

The distance between the WC and the township line cant be measured, there is nothing to measure to, that would be a calculated distance. 

One has to assume that all these measured coordinates  were measured geodeticaly, so the curvature, is already accounted for. 

Reply
Gene Kooper
Member
(@gene-kooper)
Joined: 4 years ago

500+ posts
Posts: 951

Where are you getting the 41.09?

My mistake.  It's my old weak eyes. 

The distance between the WC and the township line cant be measured, there is nothing to measure to, that would be a calculated distance.

The two standard corners were found and shot in (labeled 1 and 4) so one can measure to the township line if one believes that is the correct way to handle a closing corner situation.

Reply
aliquot
Member
(@aliquot)
Joined: 8 years ago

1,000+ posts
Posts: 1052

Right, but in the language of the test,  the true closing position would not be a "measured" distance. A big part of answering these questions is understanding the test.

Whether that is the right way to handle the CC depends on what is in the notes of the latest official survey, and any other intervening surveys. 

Reply
Protracted
Member
(@protracted)
Joined: 1 year ago

20+ posts
Posts: 33
Posted by: aliquot

The correct way to do this is the same in both manuals.

Can you be more specific as to what is the correct approach to this question (going along with the contrived standard method assumptions of the question)?

Reply
aliquot
Member
(@aliquot)
Joined: 8 years ago

1,000+ posts
Posts: 1052

6-7 (2009): "For corners reestablished by single proportionate measurement, the true point for the corner will be determined by single proportionate measurement between the witness corner and the opposite controlling corner."  

Reply
Protracted
Member
(@protracted)
Joined: 1 year ago

20+ posts
Posts: 33

6-27 (2009).  Does that math work out to answer 3 (I think it does but I'm checking here)?  If so, while I like that answer and it is how I approached the problem with the given information supplemented with some assumptions based on what was missing, it is not the answer given in the answer key.  Which has me leaning towards @dave-karoly explanation of the intention of the question and answer which is that a WC is not necessarily on line and that not enough information is provided in the question.  If this WC is not on line, then the 1/4 corner would be recovered using bearing and distance from the notes. 

Reply
Dave Karoly
Member
(@dave-karoly)
Joined: 9 years ago

10,000+ posts
Posts: 10197

To clarify, given the way the problem is presented I think C (proportion between the W.C. and the southeast section corner) is the best answer but I think the explanation for why McCavitt selected D is the W.C. is not necessarily on line therefore insufficient information is presented to calculate the position of the corner.

The question as presented is ambiguous at best and is poorly conceived, in my opinion.

Although the W.C. is not necessarily on line the way the diagram is drafted strongly implies that it is on line.

Reply
Gene Kooper
Member
(@gene-kooper)
Joined: 4 years ago

500+ posts
Posts: 951

Actually 6-27 (2009).

Reply
Protracted
Member
(@protracted)
Joined: 1 year ago

20+ posts
Posts: 33
Posted by: Gene Kooper

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.

 

That is a good way to summarize and present the answers.  Can you look at answer 3 again?  I think that record is 41.07 ch not 41.09 which I think would revise answer 3 to :

3) is 1.08 ch. south of the witness corner on a line between the witness corner and the SE Cor. of Sec. 6 at single proportionate measure. 

Reply
aliquot
Member
(@aliquot)
Joined: 8 years ago

1,000+ posts
Posts: 1052

I get 0.01' different than 3 in both northing and easting, but I doubt that is the problem. The explanation that the W.C. is not necessarily on line, can't be right, because  question B which requires an assumption that the W.C. is on line.  

Reply
Protracted
Member
(@protracted)
Joined: 1 year ago

20+ posts
Posts: 33

Posted by: aliquot

The explanation that the W.C. is not necessarily on line, can't be right, because question B which requires an assumption that the W.C. is on line.

Good point about question B!

Reply
Gene Kooper
Member
(@gene-kooper)
Joined: 4 years ago

500+ posts
Posts: 951

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.

Should be:

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 41.07 ch. and the measured is 41.454 ch., which would place the E1/4 Cor. 1.08 ch. from the WC.

Reply
Duane Frymire
Posts: 1673
Member
(@duane-frymire)
1,000+ posts
Joined: 9 years ago

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.

Reply
2 Replies
aliquot
Member
(@aliquot)
Joined: 8 years ago

1,000+ posts
Posts: 1052

I assume you are joking, but that could be confusing for someone asking for help.

Reply
Duane Frymire
Member
(@duane-frymire)
Joined: 9 years ago

1,000+ posts
Posts: 1673

No, just wasn't paying attention. Note to self: no test questions before coffee.

Reply
aliquot
Posts: 1052
Member
(@aliquot)
1,000+ posts
Joined: 8 years ago

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. 

Reply
1 Reply
Gene Kooper
Member
(@gene-kooper)
Joined: 4 years ago

500+ posts
Posts: 951

The Manual is not an excuse to not use your critical thinking skills.

The 2009 Manual often states that another method should be selected if the default method gives an unsatisfactory result.  Since I work almost exclusively with mineral survey resurveys I'm fond of the Manual adopting Meldrum's advice of:

There is no hard and fast rule for reestablishing lost corners of lode mining claims.  The method should be selected that will give the best results.

Reply
Page 1 / 3