Lecturer: Assoc. Prof. Dr. M. Zeki COŞKUN

Department of Geomatics Engineering

e-mail : coskun@itu.edu.tr

2009 – 2010 Spring Term

Lecture 1: Introduction

Contents :

Purpose and Classification of Surveying Instruments

History of Surveying Instruments

Purpose and Classification of Surveying Instruments

Good knowledge of surveying instruments enables the professional

surveyor to select the most suitable instrument for his measurements, to

operate it correctly and to utilize it efficiently.

For the determination of horizontal projection of points, instruments which

measure directions or horizontal distances are used. Furthermore,

instruments to determine the position of a point along the plumbline are

available.

For the determination of heights, instruments to measure elevations and

elevation differences are utilized.

According to the capabilities, the classification of the instruments are;

Low precision instruments; are simple and are used for simple

technical measurements, e.g. on construction sites.

Medium and high precision instruments; are used for triangulation,

traversing and levellig, to densify control nets, and for engineering

surveys.

Precision instruments are required for astro-geodetic measurements

like azimuth, latitude and time determinations, for triangulation and

1st and 2nd order levelling.

Every instrument has errors that affect the result of the measurement. In

order to obtain results free of the influences of instrument errors, one can

deal with as follows:

- the error is adjusted at the instrument such that its influence can be

considered negligible for a specific purpose of the measurement.

- one can select a surveying method which yields results free of the

influence of the instrument error

- the magnitude of the instrument error is determined and its influence is

compensated by some corrections.

Depending on the required accuracy one or more of these possibilities can

be used.

The earliest surveying instrument: The Plumb Bob

The observation that a heavy object hanging from a string causes the string to hang perpendicular to the earth is easily made.

By 2600 BC, we know the Egyptians had taken this concept and created the earliest surveying instruments: the plumb board, the A-Level, T-Level and plumb square. This was the first use of the plumb bob, against a wood frame that paralleled the surface being measured.

The worker could then make a more precise visual judgment as to the trueness of plumb or horizontal level. These earliest bobs were stone and their shape, although often egg-like, really didn't matter. These simplest of tools remained virtually unchanged for the next 4400+ years.

A Brief History of Surveying Instruments

The invention of the spirit level, and the beginnings of the Industrial

Revolution that allowed the level to be manufactured, both accurately and

cheaply, began the demise of the ancient plumb tools. For establishing

plumb and true horizontal the level is simply a better tool. It is quicker and

easier to use and just as accurate. But there is one thing the level can't do

easily, and that is to transfer an exact point from one height to another. The

plumb bob is still an indispensable tool in modern construction.

Fig. 1. Plump Bob

The ancirent Egyptian plump bob in Fig. 1 is made

of diorite with bronze ring. Unchanged in design

since 1500 B.C., this surveying tool is still used to

determine a vertical line.

Archaeological records show the use of length standards earlier than 2000

BC. An Egyptian wall painting (c. 1400 BC) depicts workmen measuring

with a knotted line similar to a modern surveyor’s chain.

Fig. 2. One of the earliest measurement

picture

The link (7.92 inches).

The fathom (5.5 feet).

The rod/ perch (3 fathoms or 16.5 feet).

The chain (66 feet).

The furlong or furrowlong (660 feet)

The mile (5280 feet or 1760 yards).

The league (3.125 miles or 16500 feet...also 198000 inches, 25000 links,

3000 fathoms, 1000 rods/ perches, 250 chains, 25 furlongs or furrowlongs).

Early standards of length were based on body measurements. The cubit was

the distance from elbow to finger tip, while the foot, palm and finger units

are self-explanatory.

Early Surveying Units:

Among the earliest length measures was the foot, which understandably

varied from district to district, and occurred in two common sizes. The first

is the foot of 246 to 252 mm based on a man’s unshod foot. The second foot

measures 330 to 335 mm and is based on hand measurements.

Other units derive from the Roman, Saxons, Angles and Jutes who each

invaded England at some time. The rod, furlong and acre are all of Saxon

origin. The mile is a compromise between the French derived Old British

mile and the Roman milliarius.

A traditional unit of distance equal to 5.5 yards (16 feet 6 inches or exactly

5.0292 meters). The rod and the furlong were the basic distance units used

by the Anglo-Saxon residents of England before the Norman conquest of

1066. "Rod" is a Saxon word which meant just what it means today: a

straight stick. The rod was defined to equal 16.5 of the new feet. This length

was called the "king's perch" at least as early as the time of King Richard

the Lionheart (1198). Although rods and perches of other lengths were used

locally in Britain, the king's perch eventually prevailed. The relationship

between the rod and the other English distance units was confirmed again

by the Parliamentary statute of 1592, which defined the statute mile to be

either 320 rods or 1760 yards, thus forcing the rod to equal exactly 5.5 yards

or 16.5 feet. (Russ Rowlett and the University of North Carolinaat Chapel Hill).

The Origin Of The ROD As A Unit Of Measurement

The magnetic compass is one of the most important instruments in the

history of surveying. The compass was probably invented by the Chinese

during the Qin dynasty (221-206 B.C.).

Chinese fortune tellers used lodestones (a mineral composed of an iron

oxide which aligns itself in a north-south direction) to construct their

fortune telling boards.

Eventually someone noticed that the lodestones were better at pointing out

real directions, leading to the first compasses. They designed the compass

on a square slab which had markings for the cardinal points and the

constellations. The pointing needle was a lodestone spoon-shaped device,

with a handle that would always point south. Magnetized needles used as

direction pointers instead of the spoon-shaped lodestones appeared in the

8th century AD, again in China, and between 850 and 1050 they seem to

have become common as navigational devices on ships.

The Magnetic Compass

The first person recorded to have used the compass as a navigational aid

was Zheng He (1371-1435), from the Yunnan province in China, who made

seven ocean voyages between 1405 and 1433 (Inventors with Mary Bellis

Shown: Early B. Rittenhouse Surveyor's Compass)

Fig. 3. Magnetic Compass

From colonial times, through the 1800’s, surveying was performed using a

crude transit or a compass and a “chain”. The most common surveyor’s

chain was 66 feet long and made up of 100 links. 1 link is equal to 1/100 of

a chain or 7.92 inches. These units of measurement can still be found in

many older deeds on record at the courthouse.

The modern steel and fiberglass measuring tapes used by surveyors are still

referred to as “chains” in deference to these early methods of surveying.

The Colonial Surveying; Compass and Chain

The compass was either mounted on a tripod or a single pole, called a

“Jacob’s Staff”. These early surveying tools were not very precise, but were

sufficient in the days when land values were 50 cents per acre, or less.

Fig. 4.Chain

Eventually, the use of the compass gave way to the transit, and the chain

to the steel tape. While the compass was generally only able to measure

the magnetic bearing of a line to the nearest one-quarter degree, a transit

is able to measure the angles between lines to less than one minute of arc.

Angles were measured with a transit and distances “measured” by optical

methods.

A rod or “Stadia Board” was graduated in hundredths of a foot, and

horizontal cross hairs in the telescope of a transit, called Stadia Hairs, were

positioned so that, based on trigonometry, at a distance of 100 feet the stadia

hairs subtended exactly one foot on the rod. Thus, within about 500 feet, a

distance could be “read” directly from the rod. Due to its speed and

efficiency, this method was most common for topographic mapping. For the

most part, stadia has also given way to electronic instruments.

Transit and Stadia

Theodolite and electronic distance measurement:

Modern Methods of Surveying

There are no exact standards differentiating an instrument referred to

as a “Transit” from one that is referred to as a “Theodolite”. Generally,

a theodolite is a much more precise instrument. Also, the angles on a

transit were read off of a circular metal plate, graduated in degrees and

minutes, while the theodolite replaced the metal plate with an internal

etched glass plate and the ability to read an angle through the eyepiece

via a series of mirrors and lenses.

By the 1970’s, relatively small, lightweight and easy-to-use electronic

distance measuring devices, called EDM’s were in use. They were mounted

on the theodolite, and operated on the principle of transmitting a narrow

beam of infrared light to a reflector and measuring the time it takes to

return.

Fig. 6. Total Station

Before long, the advance of technology and

miniaturization of electronic components enabled the

building of theodolites that measure angles

electronically, measure distances with their own internal

EDM, and display a variety of data on an LCD screen.

These super-theodolites are referred to as “Electronic

Total Stations”. In addition to enhanced speed and

accuracy, the digital data can be automatically

“downloaded” to an electronic data collector for transfer

directly to computers for calculations or CAD drafting.

The GPS satellite system (also known as NAVSTAR) was developed by the

Department of Defense for obvious reasons. There is presently a nominal

operating constellation of 24 satellites. The satellite signals received by the

general public are intentionally degraded by the DOD. The system was

never meant for civilian use.

GPS – Global Positioning System:

Fig. 7. The first GPS satellite was called GPS Block I.

Launched in 1978, it was a developmental satellite.

Another nine Block I satellites were launched through 1988.

Robotic Surveying System:

Robotic "one man" surveying systems are now readily available. These are

total stations that are remotely controlled by the use of servo-motors. This is

still a relatively new and expensive technology to implement.

This first robotic total station was made by a company called Geodometer

(now known as Trimble Navigation) in 1990.

Fig. 8. Trimble Robotic System