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Engineering Surveying
Defination
Surveying is an art of determining the rea relative position of different objects on the Earth (surface/beneath the surface) by measering horizontal distance between them and angle. The main objective of surveying is to prepare map showing the relative position of existing features on earth by which areas volumes and other requried quantities are calculated.
The uses of surveying
1. To prepare topographical map It shows towns. village I river, valley, hills etc.
2.To prepare Cadastral map It show boundaries of field house and other properties.
3.To prepare Engineering Map It shows details of engineering works like roads tunnels, building etc.
4. To prepare Millitory map. It show certain Stratagic points requeried for defence system.
5. To prepare contour Map. It shows the best possible route for roadway, railway etc.
6. To prepare archaelogical map. It shows historical objects/ structures.
Classifaction
1) Primary classifaction (curvature)
•Plane Surveying ( less than 260 km² Area)
•Geodetic surveying ( more than 260 km² area)
• Plane Surveying
→We know that the curface of the earth is Sepherical. Thus the surface is obviously, curved. But in plane surveying of earth is not considered. This is because Plane Surveying the curvature is carried out in small area. The line joining two points is taken as stright line in plane surveying
• Geodetic surveying
→ In geodetic surveying the curvature of earth is taken into account. rried out in large area i.e. more than 260 km² The line two Joining point is taken as curved line in geodetic surveying.
2)Secondary classification
1. Based on instrument used
a) chain / tape Surveying -
→The Surveying in which chain / tape is used and only linear measurement Surveying are make is called chain / tape surveying
b) Compass surveying -
→The surveying in which compase is used for angular measurements.
c)Plane the surveying:
→In this surveying measur ements and drawings are made at the same time on the field using a plane table.
d)Theodolite surveying -
→In this surveying theodolite is used to measure horizontal and vertical angle and topelchain is used to measu re distance between stations and objects.
e)Photographic Surveying:
→The surveying which is performed by clicking photos and using them to analyse Surveying the details is called photographic
2. Based on objective
a) Geological surveying -
→ Geological Surveying deals with showing village i towns, geological structure etc.
b) Mine surveying -
→The surveying which is care carried out to find mines in different. place is called mine surveying.
c)Archeological Surveying:
→ The surveying which is carried out to explore ancient structures is called archeological surveying
d)Millitary Surveying.
→The surveying which is carried out to locate strategic points for defence system is called millitary surveying.
3. Based on methods.
a) Triangulataition surveying:
→The Surveying which is performed by making number of traingles is called triangulation surveying. Chain/tape is used for linear measurements.
b) Traverse surveying-
→The surveying is performed by making numbers of traverse line is called traverse surveying. In traverse surveying compass is used for horizontal angle measurement of chain / tape is used for linear measurments. The from traverse can be open or the field. closed depending upon the feild.
4 Based on Nature of field
a)Land surveying
→This surveying is carried out on the land only. Eg Topographical survey, Cadastral surveying.
b) Marine Surveying
→ This surveying is deals with water bodies for the purpose of navigation, water supply etc.
c) Astronomical Surveying
→ This surveying is carried out to locate different point on the surface of earth by observing heavenly bodies in space.
Principal of surveying
1)To work from to part.
2)To locate a new station by the measurement of atleast to fixed reference points.
1)To work from whole to part
→ The whole area is inclosed by main stations le controlling stations and main surveylines The area is Phen divided into number of parts by forming well conditional triangle. The main. Surveylines are measured accurately by the stand chain / type. Then the side of tap triangle meacured. The purpose of working from whole to part is to prevent accumulation of error.
2. To locate new station by the measurement attest at least two fixed refrence point
→According to second principle, the me new station ch should always be fixed by the measurement of at least two refrence points. Linear measurement (Horizontal distance) is performed by chain or tape Angular measurement is performed by compass or thedolite .
Scale
→It is not always possible to represent the actual length of objects on drawing so, it is requiried to reduce or enlarge the measurement of object in order to accumate the object in the drawing sheet. The ratio by which the actual length of object is reduced or as scale. enlarged in known
Type of scale
1)Full size scale.
If the drawing is made with the size equal to that of real size of the object then it is called full sized scale.
2)Reducing scale
If the a drawing is made with the size Yess to that of real size of the object then it is called reduced scale. Eg For 1:5, 1'100, 1:500 etc..
3)Enlarged scale:
If the drawing is made with the size more than that of real size of the object it is called enlarged scale for eg : 2.1, 5.1, 10.1 etc.
Representative Fraction (R.F)
→ The ratio of distance on drawing to the correspon ding actual length of the object is known as Representative Fraction.
i-e. Representative Fraction ('R.F.) : distance on drawing/actual length of object
QN1)
If a tunnel of length 5 k-m is represented by a line of 5 cm on the drawing sheet. Find (R.F) of drawing.
Here,
actual length of tunned = 5km
length of drawing =5cm
(R.F) = length of drawing
actual length of object
or, R.F = 5/5*1000*100
or, R.F = 1/100000
R.F =1:100000
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