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| Free Software- Setting out simple curve |
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| Elements of a Circular Curve |
Portable Version Compatible with all version of Windows
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- W.C.B -Whole Circle Bearing or Azimuth Bearing
- R.B - Reduced Bearing or Quadrant Bearing
An Surveyor Compass has Reduced Bearings system in which the compass is divided into four sections, each containing 90°. The two quadrants in the northern half of the compass are numbered from 0° to 90° away from north (clockwise in the east, counterclockwise in the west). In the southern half of the compass, the two quadrants are numbered away from south (counterclockwise in the east, clockwise in the west).
Portable Version Compatible with all version of Windows
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Contours
It can be found in a topographical map, an imaginary line passing through points of equal elevations. It is one method to represent the features on earth such as mountains, depressions, undulations, etc.
Uses of Contours
1. Contour map will help in designing dams, reservoirs, roads, canals, etc.
2. To select site for new projects.
3. To check the inter visibility of stations.
4. To determine the quantity of cutting, filling and can determine the capacity of reservoirs.
Contour Interval
The vertical distance between consecutive contours is termed as contour interval. Generally the contour intervals are taken in the range of 1 to 15 m. The contour interval is inversely proportional to the scale of the map. When we have less time to complete a survey for a large area contour interval is kept larger.
Methods of Contouring
1. Direct Method: In this method a series of points are located on the ground having same elevation. For a particular contour value the staff man is directed to move right or left until the required reading is obtained, this method is time consuming but it gives accurate result.
2. Indirect Method: In Block Contouring the given area is divided into number of grids with a known interval and the staff reading is taken on the respective grid points to find the R.L values, by the method of interpolation the contour is plotted. In Radial contouring the same method is adopted but the R.L values are found on the radial lines running from the center point. This method is normally preferred on hilly areas.
Characteristics of contour lines:
· Steep slopes - contours are closely spaced
· Gentle slopes - contours are less closely spaced
· Valleys - contours form a V-shape pointing up the hill - these V's are always an indication of a drainage path which could also be a stream or river
· Ridges - contours form a V-shape pointing down the hill
· Summits - contours forming circles
· Depressions - are indicated by circular contour with lines radiating to the center
· If the middle value is higher in a contour it means it is an elevation
· If the middle value is lesser in an contour it means it is an depression
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| Chain |
Though we have got lot of advanced accurate measuring devices, chain has been preferred for the initial surveys. It is due to the reason that the chain can be used roughly in the field even it get struck with some small plants it can be taken out easily but when we are using a tape for preliminary survey the plastic tape or an invar tape may get easily damaged on rough usage. So we are preferred to use chain.
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| Tape |
It is an art of determining the relative positions of point on earth surface.Take any type of Civil Engineering Project the first step in designing a project involves surveying, because the land surface which you use for construction may not be a level surface.
To make that particular land surface into a level one or to have a certain gradient,the application of surveying is used.,to know which section has to be cutted and filled. By means of using surveying we can accurately calculate the quantity of earth work to be filled and cutted.(particular project may be a road or a building work) The other side is measuring the land area which is used for construction.
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| Total Station |
Total station is one advanced electronic instrument using which we can take horizontal angle,vertical angle ,area,height and width of a structure very accurately.Its one instrument which has the application of many old surveying instrument, also the data which you take in surveying can be transfer-ed to computer and the profile of land can be projected.
Aim:To determine the horizontal distance between two given stations of which one is in accessible and its elevation.
Instrument and Accesories Required:
Theodolite, Tripod Stand, Levelling Staff, Pegs, Arrows, etc.
Side View
Top View
Procedure:
- The theodolite is mounted on the tripod stand.
- The theodolite is centered over one of the given stations P from where the other given inaccessible station R and the staff station G can be sighted without any obstruction. The instrument is levelled using the foot screws and the altitude bubble is brought to the centre of its run.
- Station R is sighted through the telescope.
- The central vertical cross hair is made to bisect the station R and the central horizontal cross hair is made tangential to the top most point of the station R.
- The vertical circle is read and the vertical angle is recorded.
- The theodolite is then turned and the staff station G is sighted.
- The line of sight is made horizontal by setting both the verniers C and D on the vertical circle at 0°00’00” and the staff reading on station G is observed and recorded.
- Another instrument station Q is selected 20 m away from P and in line with station P and R on the same vertical plane by reversing the line of sight at P.
- The theodolite is shifted and the centered over the station Q. The instrument is levelled using the foot screws and the altitude bubble is brought to the centre of its run.
- Station R is sighted again through the telescope.
- The vertical angle is read and the vertical angle is recorded by repeating the above procedure.
- The theodolite is then turned and the staff station G is sighted.
- The staff reading on G is observed and recorded after making the line of sight horizontal following the above procedure.
- The horizontal distance between the two given stations P and R and the elevation of station R are determined from relevant trignometric expressions.
Tabulation
Inst At | Sighted To | Vertical Circle Reading | Remark | ||||
Vernier C | Vernier D | Mean | |||||
° | ‘ | “ | |||||
P | R | ||||||
Q | R | ||||||
Formulas
S=S1-S2 =h2-h1
h1= D tan(Angle P)
h2= (D+ 20) tan (Angle Q)
(D+ 20) tan (Angle Q) - D tan(Angle P) = S1-S2
(D+ 20) tan (Angle Q) - D tan(Angle P) = S
D(tan(Angle Q) – tan( Angle P)) = S – (20tan (Angle Q))
D = S – (20tan (Angle Q)) / (tan(Angle Q) – tan( Angle P))
Result: Thus the horizontal distance between the two given stations and the elevation of the given stations are determined
- Horizontal Distance PR =
- Elevation of R =
Aim:To determine the gradient between two stations by the principles of statia Tacheometry.
Instrument and Accesories Required:
Theodolite, Tripod Stand, Levelling Staff, Pegs, Arrows, etc.
Side View
Top View
Procedure:
- The theodolite is mounted on the tripod stand.
- The theodolite is centered over an arbitrarily selected station P from where the staff stations A and B can be sighted without any obstruction and the instrument is levelled using the foot screws and both the plate bubble and the altitude bubble are brought to the centre of their run.
- The theodolite is set on the face right mode and the vernier A on the face right mode and the vernier A on the horizontal circle is initially set at 0°00’00” and the staff station A is sighted.
- The central vertical cross hair is made to bisect the staff station A and the central horizontal cross hair is made tangential to 2.5 m mark on the staff station.
- The horizontal and vertical angles are recorded by reading the horizontal and vertical circles respectively.
- The stadia hair readings for the staff station A are also observed and recorded.
- The theodolite is swing to the right and the staff station B is sighted.
- The central vertical cross hair is made to bisect the staff station B and the central horizontal cross hair is made tangential to 2.5 m mark on the staff station B.
- The horizontal and vertical angle are recorded by reading the horizontal and vertical circle respectively.
- The stadia hair readings for the staff station B are also observed and recorded.
- The observations are closed on the first staff station A.
- The theodolite is then set on the face left mode and the horizontal and vertical angles and the stadia hair reading are observed for both the staff station A and B are recorded by repeating the above procedure for the initial settings of 180°00’00” on vernier A. The staff stations are sighted in the same sequence as above but by swinging the theodolite to the left.
- The average of the horizontal angles subtended by the line AB at the instrument station P and the vertical angles are found.
- The average vertical angles and the staff intercepts are substituted in the relevant expression for horizontal distance for inclined line of sight and vertically held staff and the horizontal distances of the staff stations A and B from the instrument station P are determined by the principles of stadia tacheometry.
- From the mean value of the horizontal angle APB and the horizontal distance PA and PB, the horizontal distance AB is determined by the cos rule.
- The difference in elevation between the two staff stations A and B is also determined.
- The gradient between the two staff stations A and B is determined from the difference in elevation and the horizontal distance between them.
Tabulation
Inst At | Sighted To | Horizontal Circle Reading -Vernier | Included Angle | Average Included Angle | Vertical Circle Reading - Vernier | Average Vertical Angle | Stadia Hair Reading | ||||||
A | B | Mean | C | D | Mean | Top | Middle | Bottom | |||||
P | APB | Angle A Angle B | |||||||||||
Formula
PA = KSACOS2(Angle A) + C COS (Angle B)
PB = KSBCOS2(Angle A) + C COS (Angle B)
Horizontal Distance between AB can be obtained by using Cosine rule
AB2 = PA2 + PB2 – 2PA x PB Cos APB
h1= 2- PAtan (Angle A)
h2= 2- PBtan (Angle B)
Difference in elevation between A and B = h2- h1
Gradient from A to B = Vertical distance AB/ Horizontal distance AB
Result: The gradient between the two stations is determined.
The gradient between the two stations A and B is 1 in ____
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