Surveying ERRORS

Error Management

Some amount of error is acceptable - acceptable error is determined by the intended use of the measurement. 

(for example: if you are setting construction stakes from which to build concrete curb and gutter, in flat terrain ,we probably need to set those to nearest 3mm so that we prevent the formation of puddles(გუბე) 
    for preliminary dirt work on a subdivision site heavy equipment can only measure or only cut 30mm)

Most construction surveys require 3rd order accuracy 

Good leveling procedures are designed to minimize (cant eliminate) systematic and random errors. (like instrument calibration) 

Leveling Accuracy Standards

1st order accuracy:

provides basic framework for the National Spatial Reference System and precise control  of large engineering projects and scientific studies.

2nd order accuracy:

adds to the basic framework for major engineering projects 

3rd order accuracy:

servers as vertical reference for local engineering ,topo, drainage and mapping projects.

the majority of benchmarks are 3rd order benchmarks.

Systematic Error :

Can be measured / quantified   

Has a Positive or Negative value (მაგ.იარდ სტიკით/folding meter გაზომილი ციფრი რომ შეგეშალოს მეტრებში ანუ imperial/metric bullshit. difference between a meter and a yard is a fixed value, შეიძლება ვარგისი იყოს მაგრამ Has a Positive or Negative value)

Random Error : 

Accidental/ Blunder (we cant quantify because all we know that it exists)

Can not be measured / quantified

(მაგ.misread the rod)

             systematic  error sources: 

Earth curvature & refraction (when the distance to your rod is less then 91m this becomes a very tiny error , but when its 180 or 300 you may include earth curvature and  refraction corrections (trigonometric lvling))

Maladjusted instruments 

Temperature effect on level rod (metals expend as they heat up and contract as they cool. if we use wood rods with lightweight metal faces. fiberglass  is ok)

Level Rod is not plumbed (its systematic error only if you know the slope of the rod, otherwise its random error)

           random error sources: 

Instrument not level

Bad rod reading

Poor turning point (TP needs to be stable to maintain its position, elevation long enough, to take a foresight reading, to allow the instrument to a new location and level it and long enough to take a new back sight in order to establish aN H I at that new instrument location. things like loose rocks on the surface do not make good turning points. 

Parallax (პარალაქსი (საგნის მდებარეობის ხილული ცვლილება დამკვირვებლის თვალის გადანაცვლების შედეგად) is an optical error induced by the mismatch of the focal length of your eye and the focus lenses of your instrument. when those two focal lengths come into harmony then parallax is eliminated)

Heat wave effects  heat waves affect your ability to see across hot surfaces ,you've noticed shimmering effect (ციმციმი) of the sun beating down on a reflective surface 

Wind - blowing rod out of plumb, legs of tripod make them vibrate