Replies to This Discussion

Permalink Reply by A Murali babu on October 17, 2016 at 1:04am

Dear Mat,

Please let me know for what kind of misclosure you require, whether its for closed or open traverse. I can send you the excel template accordingly.

Regards

A Murali babu

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Permalink Reply by Adeulure victor on October 17, 2016 at 2:13pm

Surv. A Murali babu, please can u send to me the excel template for traverse or for that of spot heighten

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Permalink Reply by J. Anthony Cavell on October 17, 2016 at 2:03pm

Dear Mr. Win,

A first test is to draw out the traverse in one direction.

Then draw it out in the reverse from the end to the beginning.

Frequently the graphics will indicate to you whether the error is linear or angular.

JAC

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Permalink Reply by uzoewulu uzochukwu on October 18, 2016 at 3:34am

Dear JAC,

truly, I have never come across this your method of identifying errors in the the distance/and or bearing measurements.

Could you please explain better with the aid of a drawing.

Regards.

Uzo.   

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Permalink Reply by J. Anthony Cavell on October 18, 2016 at 8:39am

Mr. Uzochukwu,

Your profile reads, in part, 

"Licenses, Certifications or Awards

B.SC Surveying and Geoinformatics

I have experience with the following

GPS, cadastral, topographic, boundary surveys, construction staking, topographic surveys, control network surveys, Survey Office, Construction, Cartography

How many years have you been surveying?

10

Most comfortable with the following types of instrumentation

Total Stations, GPS, Automatic Levels, theodolite, compass"

Surely with 10 years experience you have had the occasion of drawing a survey. Simply draw the survey as if it goes from the start to the finish. Then draw it backwards. Then observe at which leg(s) the two diverge, either by length or direction.

JAC

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Permalink Reply by Adeulure victor on October 17, 2016 at 2:12pm

Surv. A Murali babu, please can u send to me the excel template for traverse or for that of spot heighten

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Permalink Reply by J. Anthony Cavell on October 17, 2016 at 2:25pm

Check any surveying text book. This involves no more than elementary coordinate geometry.

JAC

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Permalink Reply by A Murali babu on October 18, 2016 at 12:56am

Dear Friend,

PFA Files as required by you.

Regards

A Murali babu

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• BowditchMethodClosedTraverse.xlsm, 128 KB
• TraveseClosureFromKnownCoordinatesBearingDistance.xlsm, 87 KB
• TraverseCorrectionfromKnownco-ordinates.xlsm, 93 KB

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Permalink Reply by Dave Drahn on October 17, 2016 at 7:51pm

That's interesting.  I never learned that one.  Thanks.

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Permalink Reply by CHARLIE B. AYCOCK, III on October 18, 2016 at 10:08am

Yes, that is interesting but there is usually more than one way to skin a cat. I like Mr. Cavell's reply. I could solve such a problem quicker than I can describe how to do it! It sounds like a blunder. If the traverse is plotted from different POBs, the error should be obvious. Plotting it on paper works but a computer screen using cogo is easier. Should the error be systematic, you have a real problem. It could be your equipment & you should probably remeasure the angles &/or distances. I think least squares is the accepted standard for adjustments. You can't adjust a blunder or bad measurements from bad or out of calibration equipment. You can make adjustments for a systematic error if you can figure out what it is, if you want to go that route. I prefer to remeasure as that is the best & safest method & often the quickest. If you find the blunder, you still have to remeasure the suspected course & distance anyway, if you want to do it right. With the equipment available today, there isn't usually much to adjust, unless you are transforming rectilinear coordinates to geodetic coordinates or vice versa. Closures of 1/50,000 are the norm & anything over 1/10,000 & you can start looking for a bust.
Software is ever changing & so is the way we collect data, the math & principles of surveying remain the same. Nobody likes to change the way they are accustomed to doing things. I once had a professor of structural engineering as a supervisor. He would go into a coma if anybody mentioned the "metric system"!

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Permalink Reply by Alexander Montgomery on October 21, 2016 at 2:57am

Completely agree Charlie but I will go further in that all these suggestions give me a clue to where to begin looking for the error but the only thing to do is to remeasure. I also dislike the trend of applying least squares adjustment as it is a statistical adjustment based on matrices and I feel If I can justify applying more weight to one leg over the others then I should have spent the extra time to ensure that one leg was surveyed to the same standard originally. I prefer applying Angle balance and Compass adjustment or Crandall adjustment (which I believe is similar to Bowditch).

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Permalink Reply by William Robinson on October 23, 2016 at 7:35am

I think both you and Charlie are both right to say to get back out there and re-measure. I find it hard to understand how people would get gross errors with the instruments that we have today unless there was a problem with the instrument in question. I have actually posted a video of an application that I wrote for Android mobile phones in which you can quickly plug in all your observed traverse data (Meaned angles of course) on site. This app will calculate angular miss-closure, coordinate miss closure. If you are happy with the results the app will then balance the angles and if necessary apply the bowditch correction rule to finalise coordinate precision. The data can then be copied and sent out via the devices share function. All this can be quickly rattled out before you leave the site so if there are any errors that can be dealt with on site, they can be sorted there and then. Not sure why but people here have have not really bothered to show an interest in the app.

It's Here: http://landsurveyorsunited.com/video/survengtrav

To anyone reading this reply please have a look and I would be grateful if you could give me some feed back

Thanks

Will.

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