Units - Introduction

Basic of traditional or typical plane surveying are:
1. horizontal distances,
2. vertical angles,
3. zenith angles,
4. horizontal angles,
5. vertical distances,
6. slope distances.

Most common employed units are:
1. length,
2. area,
3. volume,
4. angle.

Two different systems are use in specifying of measured quantities:
1. English system,
2. Metric system (International System of Units - SI)

Levelling - Definition - Part 1

Vertical Line - A line that follows the direction of gravity as indicated by a plumb line

Level Surface - A curved surface that at every point is perpendicular to the local plumb line. Level surface are approximately spheroidal in shape. A body of still water is the best example.

Level line - A line in a level surface - a curved line

Leveling - Introduction

Leveling - applied to any of the various processes by which elevation points are determined.

Leveling commonly used to:-
1. Design highways, railways, canals and other facilities having grade lines
that best conform to existing topography.
2. Lay out construction project according to planned elevations
3. Calculate volume of earthwork
4. Investigation drainage characteristic of an area
5. Develop map showing general ground configuration
6. Earth study subsidence and crustal motion

Source: Wolf, P. R. & Ghilani, C. D. (2002). Elementary Surveying: An Introduction to Geomatics. (10th ed.). Prentice Hall, US.

Geodetic Instrumentation and Methods

Surveyor very familiar with tools to measuring angle and distance. With new technology, the survey tools such as electronic theodolite and total station become sophisticated. Manufacturer also produce robotic function in total station. Robotic total station equipped with servo drive mechanism. With this mechanism, that instruments enable to aim automatically at a point to be set or to track the moving target.

Robotic Total Station (my choice) Leica TPS-System 1000 instruments version TC2003 or TCA2003 (picture),

The performance of TPS1000 version TC2003 and/or TCA2003 :-

Angle measurment accuracy 0.5" or 0.15 mgon

Distance measurment accuracy 1mm + 1ppm

Searching accuracy (TCA version) up to 200m 1mm

Leica Geosystems (http:// http://www.leica-geosystems.com/).

Deformation Monitoring

So what is deformation monitoring?

From Wikipedia, the free encyclopedia
http://en.wikipedia.org/wiki/Deformation_Monitoring

Deformation monitoring is the systematic measurement and tracking of the alteration in the shape or dimensions of an object as a result of the application of stress to it. Deformation monitoring is a major component of logging measured values that may be used to for further computation, deformation analysis, predictive maintenance and alarming.

Deformation monitoring is primarily related to the field of applied surveying, but may be also related to the civil engineering, mechanical engineering, plant construction, soil and rock stability mechanics.

According to [2], deformation surveys are mainly carried out to investigate crustal movement, slope stability, glacier and shelf ice movement, ground subsidence and deformation of man-made engineering structures.

The determination consist from design, measurement and analysis stage [3].

The measurement technique generally divided into geodetic and geotechnical/structural methods.

a) Geodetic method: conventional & terrestrial survey and space-based method. Global information
b) Geotechnical/structural: Local information (strain gauge, piezometer and inclinometer). Short distance and small area coverage

Nex Post : Detail about geodetic deformation monitoring.

References

[1] Vanicek, P. and Krakiwsky. E. (1986). Geodesy: the concept. Second edition. (Amsterdam: Elsevier)

[2] Caspary, W.F. (1987). Concepts of network and deformation analysis, School of Surveying, The University of New South Wales, Monograph 11, Kesington, N.S.W.

[3] Halim Setan (1995). Functional and Stochastic Models for Geometrical Detection of Spatial Deformation in Engineering: A Practical Approach. City University, PhD Thesis

Why Surveyor Concern About Accuracy & Precision - Part 2

What is systematic errors?
- It result from factor which comprise the measuring system and include the enviroment, instruments and observer.
- Systematic errors also known as biases
- In systematic errors, if system condition remain constant, the systematic error will likewise remain constant. If condition change, the magnitudes of systematic errors also change

Source of errors : instrumentation and natural condition

Solution : can be model mathematically

Situation of systematic errors
(a) Constant systematic error - use of 100m tape that has been calibrated and found to be 0.02 too long. It introduce a 0.02m error each time it is used
(b) two-peg test - to eliminated collimation error

Why Surveyor Concern About Accuracy & Precision - Part 1

observations are never exact and will always contains errors. High tech instrumentation only can reduce error size or also the proper procedure only make sure the the errors to within tolerable limits.

Theory of Errors in Observation - Introduction

Making observation or doing measurements and subsequent computation & analysis using them are fundamental task of surveyor. We surveyor must be good observation skill & high tech mechanical equipment to get good measurement. But no matter how good and carefully the observation made, observation are never exact and will always contain errors.

Surveyor must have a knowledge to understand the different kind of errors, their source and expected magnitudes under varying conditions and their manner of propagation.

For more technical,

"surveyor are usually faced with the problem of estimating some unknown quantities (parameter). This is done through collecting several measurement of some kind known as observation - and then adopting the appropriate mathematical model relating both observation an0d unknowns."

ERROR: difference between observation of quantity and the true value (which can never be known)

true error (E) = observed value (l) - true value (t)

since true value (t) can never be known, true error (E) will never be known as well.

Errors in observation occur from several sources such as

1. Personal - Limitation of the observer - the ability to repeat the same measurement - carelessness of the observer

2. Instrumental - due to imperfect construction

3. Natural - Due to changing environmental condition in which the measurement are made.