Hi All

I hope this post find everyone well and in good health

  1. Explain how differences in heights are reduced by adapting the raw   

              measurements to refined data. Explain reductions relating to sea level, close,

              and mean. 

Any help would be appreciated

Regards

MAt

This Content Originally Published by a land surveyor to Land Surveyors United Network

Views: 456

See Your Saved Posts Timeline

☇ Reply to this

Replies to This Discussion

I need a more clear question. What's your survey project and are you dealing with littoral data???

Dear Mr. Win,

I will try to give an explanation, but first, here are a few links to previous comments.

Link 1
Link 2
Link 3

Link 4
Link 5

  • Explain how differences in heights are reduced by adapting the raw measurements to refined data.

Perhaps the best short explanation I have is to consider people who speak different languages but who think it is the same one, e.g., Britain and U.S. natives. Some of the sentences almost make sense but some of the words used need to be correlated.

Let's take a simple example of elevations in which the measured elevations seem slanted. They are higher on the east  relative to the ones on the west. If our project controls are supposed to rule the project and adjustment of our observations by tilting your observations until they agree with the control. that was an oversimplification, of course, but not too far off.

An adjustment (or localization/calibration) develops the necessary functions to bring your observations into conformity with the control. Adjustment can be quite simple or ridiculeslycomplex, but their purposes are to do what I described.

Often one or more observations or control points will prove to be outliers and removed from the process.

  • Explain reductions relating to sea level, close, and mean.

MSL:  Sea Level is an average value of the level of the sea at a tide guage over an 18.6 year period, the time it takes for all the influences on the tides to cycle through.

At one time, (in large part because running levels for any great distance was a daunting task) the CSG&GS took the MSL at several guages around North America averaged their MSLs and developed the MSL29 vertical datum. It bacame obvious that these were not actually MSL, so the datum was renamed NAVD29. Since leveling was a local affair it served until the 1980s.

We now have a better datum, a hybrid datum called NGVD88. Its zero is far more consistent but NOT MSL because MSL only exists at a tide guage. So much for MSL. Except at tite guages, we don't know where MSL is.

Close:  I presume you mean the verb close = to shut. In surveying parlence, to close means for an observation to agree with a previous one. A level loop closes if the ending value is the same or very nearly the same as the original value.

Mean:  Again, I'm not sure of your request. Mean = simple average of some numbers.

I hope you find this helpful.

JAC

http://opencommons.uconn.edu/thmeyer_articles/2

What Does Height Really Mean

Meyer, Roman, Zilowski     2006

Yes! Tom's, Dan's and Dave's essay is a great source.

Thanks, Mr. Noblitt.

JAC

im guessing the question is written way that everyone interrupts it differently.

The explanantion is meant to include or show how differences in heights are reduced by adapting the raw measurements to refined data. Their explanation must cover reductions relating to sea level, close and mean. Explanations may include these points:

Curvature and vertical refraction zenith angles measured for horizontal and vertical reduction of long lines require curvature and refraction corrections.

The manufacturer’s specifications for most total stations indicate that the earth's curvature and atmospheric refraction are internally computed and the corrected horizontal and vertical distances displayed. This correction can be eliminated (or balanced) by taking the mean of two reciprocal measurements.

The reciprocal procedure means that a distance and a zenith angle are measured at point A to point B and then from point B back to point A.

At longer distances -- over 1000 meters (3280.8 feet) -- it is better to use this averaging solution than the on board correction factors provided within these total stations, even when they are in perfect adjustment.

i maybe readying into the question way too much who knows

thanks for your help tho

Cheers

Mat

RSS

Where Thousands of Professional Land Surveyors, Students of Surveying and Educators are United through Collaborative Knowledge and Purpose.

Land Surveyors Forum

Survey Abstract Coordinates

Started by John J Rodriquez in Introduce Yourself to the Community. Last reply by Kevin D. Allen yesterday. 13 Replies

Control surveying problem

Started by shree ram bhandari in Land Surveying Jobs. Last reply by Billy Brooks yesterday. 11 Replies

Magnetic North Update

Started by Billy Brooks in Surveying Best Practices. Last reply by Billy Brooks Feb 6. 2 Replies

AERIAL STEREOSCOPY

Started by Lalith Senanayake in Surveying Related Links. Last reply by shree ram bhandari on Tuesday. 4 Replies

Job Quotation

Started by Nitesh Shrestha in Land Surveying Jobs. Last reply by Nitesh Shrestha Jan 21. 3 Replies

Survey under tree canopy

Started by Massimo in Surveying Best Practices. Last reply by Maurice Heter yesterday. 7 Replies

Mean Sea Level (MSL)

Started by Chuck Turlington in Geospatial Industry Types. Last reply by Kim Noblitt Jan 17. 6 Replies

Surface pro

Started by Malik in Surveying Field Tips and Tricks. Last reply by Kevin D. Allen Jan 7. 5 Replies

ROOF PEAK SURVEY

Started by Mthulisi Mloyi in Professional Advice for New Surveyors. Last reply by ⚡Survenator⌁ Jan 4. 2 Replies

Tools,Apps and Quick Guides

DEDICATED TO THE MEMORY OF SKIP FARROW (1953-2015)


Help With Survey Equipment

Social Support For Equipment

Surveying Video Categories

Surveying Photo Categories

United States Hub Forums

International Surveyor Hub Forums

Resources for Company Owners

Land Surveyor Social Media

Surveyor Resources Collections

Getting Started & Newsletter

Featured Land Surveyor Hubs

Student Surveyors

71 members

Surveyor Birthdays

Surveyor Birthdays Today

Surveyor Birthdays Tomorrow

© 2019   © Created by Land Surveyors United   Powered by

Badges  |  Contact LSU  |  Privacy Policy  |  Terms of Service

Site Explorer