What is Surveying |introduction ,defination. History of survey in ancient

INTRODUCTION

Definition

 Surveying is  the process  of determining  the relative position  of natural and manmade features  on or under the earth’s surface, the presentation of this information either  graphically in the form of plans  or  numerically in  the form of  tables, and the setting out  of measurements on the earth’s  surface.  It usually involves measurement, calculations, the production of plans, and the determination of specific locations.

 The  surveyor  may be  called on  to determine heights and  distances; to set out buildings, bridges and  roadways; to determine  areas  and volumes and to draw plans at a predetermined  scale.

Types

There are two major  categories  of surveying: 

1. Plane Surveying . 

Plane  surveying deals  with  areas of limited extent and  it is assumed that the earth’s  surface is  a plane and therefore no corrections necessary for the earth’s  curvature.

2. Geodetic Surveying.

 Geodetic surveying  is concerned  with  determining the size  and  shape of the earth and it also provides  a high-accuracy framework for the control of lower order surveys.  The highest  standards  of accuracy are  necessary. Geodetic surveys cover relatively large areas  (eg a state or  country) for which the effects of earth curvature must be considered.

Branches

1. Topographic  Surveys are  concerned with the measurement and  mapping of the physical features  of the earth. These features  are all natural  and manmade features.
2.Engineering Surveys cover  surveys  carried out as  part  of the preparation for, and  carrying  out of, engineering works,  including  roads, railways, pipelines, drainage etc.
3. Cadastral  Surveys are concerned  with the measurement, definition and mapping  and  recording of property boundaries.
4. Hydrographic Surveys are those  made  for determining the  shape  of the bottom of lakes, rivers,  harbours and oceans. They also include the measurement  of the flow  of water in  streams and the estimation  of  water resources.
5. Aerial Surveys are made  from an aeroplane, and for the purpose of  mapping the terrain.  The  control for such  a  map  is obtained  from ground  surveys,  but the details  are obtained  from aerial  photographs.  This includes making measurements and interpretations from aerial photographs.
6. Astronomic Surveys are surveys made  to determine  the latitude, longitude and azimuth from observations to the stars.
7. Mining Surveys are those made to  determine  survey  control for the development  of both surface and underground mines  within the mining industry, and the determination of volumes in mine production.
8. Computing is  a specialised area of  surveying  where complex  computer programs  are  used to solve problems within the surveying industry.
9. Consulting  is  another specialised  area of  surveying where  specialist surveyors are hired for a  short period  of time to advise on the  requirements for a specific  task  or to perform the specific surveying

History of surveying

• It is quite probable that surveying had  its origins in ancient Egypt. The Great Pyramid of Khufu at Giza  was built  c.  2700 BC, 755  feet long and  480 feet high. Its nearly perfect squareness and north-south orientation affirm the ancient Egyptians'  command of surveying.  
• Evidence  of  some  form  of  boundary  surveying as early  as  1400  BC has  been found in the fertile valleys and plains  of the 
• The Egyptians had the groma, which  was used to  establish  right angles. It was made  of a  horizontal wooden cross,  pivoted at the  middle and  supported from above. From  the end of  each  of the  four  arms  hung  a  plumb bob.  A plumb  bob  is a  shaped weight  that hangs  from a string.  Because  of  the  weight, the string  will always  be vertical. 
• The  Greeks  used a  form  of log line for recording the distances  run from point  to point along the  coast while making  their  slow  voyages from  the Indus to the Persian Gulf  about 325 BC.  
• The  Greeks  introduced the astrolabe,  which is  an instrument to  measure the altitude of stars  above the horizon, in the 2nd  century BC. It took the form  of a graduated  arc  suspended  from  a  hand-held  cord. A  pivoted  pointer that  moved over the graduations  was pointed at the  star. The  instrument was not used  for nautical surveying for several centuries, remaining a scientific aid  only. 
•  During their occupation  of Egypt,  the Romans acquired Egyptian surveying instruments, which they improved  slightly  and to which they added  the water level and the plane  table. 
•  About 15 BC  the Roman architect and engineer Vitruvius mounted  a large  wheel of known circumference in a small frame,  in much the same fashion  as the wheel is mounted on a wheelbarrow; when it  was pushed  along the ground by hand  it automatically dropped a  pebble into a container  at each revolution, giving  a measure of the distance travelled. It  was, in effect, the  first odometer.
• Arab traders  brought the magnetic  compass  to the  west in the 12th century AD.
•  Plane tables  were in  use in  Europe in the 16th  century. Surveyors practised the principle  of  graphic triangulation  and  intersection.  In 1615  Willebrord  Snell,  a Dutch mathematician, measured an  arc of  meridian by  instrumental  triangulation.  
• In 1620 the English mathematician Edmund  Gunter  developed a surveying chain, which was  superseded only by the steel tape in the beginning of the 20th century. 
• By the late 18th century modern surveying can be said to have begun. One of the most  notable  early feats  of  surveyors  was the measurement in  the 1790s of the meridian from  Barcelona,  Spain, to  Dunkirk,  France, by two  French engineers, Jean Delambre and Pierre  Méchain. This was to establish the basic  unit for the metric  system  of measurement.  
• Many improvements and  refinements  have been incorporated in all the  basic surveying instruments. These  have  resulted in increased accuracy and  speed  of operations  and have opened up possibilities  for improved methods in  the field. 
• During the  nineteenth  century, the combination of a hot air balloon  and a  camera were used to produce maps and plans. It was difficult to survey large areas because the  balloons  were slow  moving and a  new  photographic  negative had  to be loaded into the camera after each  photograph  was taken. In 1862 union soldiers used  cameras mounted in hot air balloons to  map behind the  confederate lines. 
• It was not until the turn of the twentieth  century, with the developments of the aircraft and invention of the roll of photographic film, that aerial photographs started to be  used  extensively within the survey industry. 
• The first light  wave Electronic  Distance  Measurement instrument  was developed in 1943 to measure the velocity of light. Once the velocity of  light was known, it was then possible to reverse the process  so that a distance could  be measured. 
• In 1954, the light wave was replaced  by a radio wave to increase the distance that could be  measured. In the late 1960s, lasers were first used with EDMs. 
• In the mid to late 1970s, the United States of America sent their first Global Positioning System satellites into space.  The final  development  was the extensive use of computers to perform most common data  processing and recording  of survey data. 

Procedure of surveying

The following  sequence  of steps is  commonly followed  when  carrying  out  a survey: 

(i) Reconnaissance.  

During the  reconnaissance  phase, the  surveyor will  obtain an overall picture of the area that the project will be conducted in. They will  select  where the control points will be located, the accuracy required for the control, and  which survey instruments  will be required for the project. 

(ii)  Measurement  and Marking . 

During the measurement  and marking  phase, the  surveyor  will perform  all the observations  in the field required to accurately determine the control points, as  well as  placing and observing to any  temporary  points  such  as  wooden pegs. They  would also  perform  any  calculations  from the  observations,  such as angular  and linear misclose and area  and volume  calculations. 

(iii)   Plan  Preparation. 

 During the  plan preparation phase, the  calculations that were performed from the field observations would be further enhanced and used to produce the final plans for the project.

Responsibilities of a Surveyor. 

 The responsibilities of the  surveyor  are  many and varied, but can generally be reduced to the following:
1.  Responsibility to the Task.
The  surveyor is  responsible for completing the task required in the most efficient manner and in the  time available. All effort must be made  to ensure that the information supplied by the surveyor  is as  accurate  as  is  possible to  complete the task.  Not all tasks require the same order of  accuracy. By an understanding  of the task the surveyor  must decide on  the accuracy to  be achieved.
2.  Responsibility to the Client or Employer
 The surveyor has a responsibility to the  client or employer to produce what the client requires, within the budget restraints. This may need   patience and tact in  explaining to  the  client the  limitations to  a task.
3.  Responsibility to the Community.
The  surveyor has  a responsibility to the community  in general, to ensure that work undertaken by his team does not damage property or interfere with members of the community. Permission must  be sought  before  accessing private property  or before removing  trees or  shrubbery  to enable survey measurements.
4.  Responsibility to the team .
The surveyor, as the leader of the survey team, has a responsibility to the members of that team  and  must ensure  that their needs are met  regarding their leave, pay, OH&S etc. The surveyor has a  responsibility to  ensure that  all members of the team receive the training needed, not only to complete the  task  at hand,  but also to enable them to advance within their chosen professions.

Role of a Surveyor 

The  role  of the surveyor  is  that of the  leader of the team. With  that  role  come  the responsibilities  outlined above.
 The  role  of the surveyor  is  to perform  the measurements  necessary to  complete any task  required.

Tasks of a Surveyor 

The tasks performed by a  surveyor  will depend on which branch of  surveying they practise  in. The most common tasks involve the determination of height and distances.
1. For the Cadastral Surveyor, the main tasks involve the determination of property boundaries.
2. For the Topographical Surveyor, the main  tasks involve the location of  detail  on the earth’s  surface for the production of maps.
3. For the Engineer Surveyor, the main tasks include  the setting  out of buildings, sewers, drains, bridges and roadways;  determining areas and volumes of  regular and irregular  figures; the preparation  of detailed drawings and plans.
4.  For the Mine  Surveyor, the main  tasks include the setting out of mine  lease boundaries and the calculation of end-of-month volumes.

Categories: Engineering Trends, Surveying