How to estimate Plane Surveying and it's different methods
The Basics of Plane Surveying
Plane surveying is a form of surveying where the earth is assumed to be a flat surface, it's curvature is not taken into account.
In this kind of surveying two points are first considered, a line joining these two points are treated as a straight line. The triangle produced by any three points is known as the Plane triangle and the angle produced is known as the Plane angle.
If we compare this type of survey with Geodetic surveying the accuracy is pretty much low. However, American Surveryours defined the limit of 250 sq km of treating the survey as plane survey.
Types of Survey
Based on the nature of the field, surveying can be done in different methods. In this article, we will discuss about the different methods of survey.
This is the most primitive method of surveying. If you want to do surveying in the most simple form then you can choose this type of surveying. In the chain survey, measurements are taken in the field whereas plotting and calculations take part in the corporate offices. The pivotal point of chain survey is, here no angular measurements are taken, whereas only linear measurements are considered.
If one needs to survey small areas with minor details one can always opt for Chain surveying.
The requirements for chain surveying are mentioned below:
- Cross staff
- Ranging Rod
2.Plane Table Surveying
In this type of Surveying the plotting work and the fieldwork are done simultaneously and no office work is required.
It is mainly used for small scale or medium size mapping. The equipment required for plane table surveying is very simple and is available everywhere. The equipments are described below:
- Drawing Board
- Spirit Level
- Trough Compass
- U-frame or plumbing Fork
- Water Proof Cover
- Paper or Drawing sheet
The drawing board is made up of well-seasoned Timber wood and is mounted on a tripod with a levelling head in such a way that it can be levelled or revolved about a vertical axis. Normally the size of the drawing board varies from 40 cm x 30 cm to 75 cm x 60 cm or 45 cm square, 60 cm square, etc.
An Alidade is a ruler which is used on a plane table for bisecting objects, drawing direction lines, rays etc. The alidade may be plain fitted with sight vanes at both the ends, or it may be equipped with a telescope. One of the sight vanes has a narrow rectangular slit. While the other vane has a central vertical hair or wire.
If the alidade is telescopic, the telescope is provided with a vertical circle, and a level tube is fitted with cross-hairs.
With the help of the spirit level, the table can be levelled by putting in two positions at right angles to each other.
The setting of the spirit level and the plane table must be in such a way that the bubble is central in both positions.
Trough compass is normally used to indicate the direction of the magnetic meridian on plane paper.
U frame or Plumbing Fork
The U fork is a metal strip bend in the shape of U having equal arm length. The top arm is pointed and bottom arm carries a hook for suspending a plumb bob.
The main function of the waterproof cover is to save the drawings on the paper from rain and water.
The main function of the Tripod is used to fix the drawing board.
Compass Surveying is the one in which the traverse work consists of a series of the lengths and directions and which is measured with tape or chain and with an angular instrument.
Purpose of Compass Surveying
Normally Compass Surveying is conducted in the following situations.
- When there is loads of work pressure and the survey work needs to be completed quickly
- When the chaining is difficult and the area is hilly
- When the whole area cannot be segregated into a network of triangles
- When the area long, narrow it is too large to be surveyed, one can use Compass Surveying in this situation.
- When the geographical area is covered by dense forest, compass Surveying is the best option to conduct the survey.
Types of Compass used in Compass Surveying
The major types of Compass used in this type of Surveying are :
- Prismatic Compass
- Surveyor's Compass
- Level Compass
Advantages of Compass Survey
The main advantages of Compass Survey are specified below:
- They are light and very much portable
- It helps to retrace old surveys
- The error produced in a single survey line does not affect the other lines.
4. Theodolite Surveying
For building constructional work theodolite surveying is mainly used.
Theodolite is an electronic measuring instrument, used to analyze the horizontal and vertical angles along with a tiny low telescope that may move with the horizontal and vertical planes. In construction, it is mainly used in the housing industry for measuring horizontal and vertical angles and scaling functions.
Theodolites are placed everyplace from construction sites to main road points. Theodolite plays a pivotal role in the measurement of vertical bearings, horizontal and vertical angles.
For example, to measure huge buildings escalating edges, Theodolites are used. It is also used for determining highway points. Theodolites use paradoxical faces and swings to produce more curved of readings.
Uses Of Theodolite
Listed below are the uses of Theodolite
- It is used to locate points on a line
- It is used to range curves
- To determine the difference in levels
- To set out the grades
Advantages of Theodolite Survey
The advantages of theodolite survey are listed below
- For accurate result and correctness of reading, it is used
- It gives electronic readings.
- It is not affected by weather factors
- Horizontal circles are arranged with any other value
- It does not give repeat readings
Levelling is a form of Surveying to measure levels of different points with respect to a fixed point such as elevation of a building.
Types of Leveling
There are different types of Leveling in surveying
- Trigonometric levelling
- Barometric Leveling
- Direct Leveling
- Stadia Leveling
The process of Leveling in which the elevation of the point is measured from the vertical angles and observed horizontal distances in the field is called Trignomatric Levelling.
In this process of Leveling atmospheric pressure of two different points are observed based on which the vertical difference between two points are determined through Barometer. It is an approximate estimation and is very rarely used.
This is the most widely used process of leveling, It is also called as spirit leveling. The spirit level is mounted on the telescope of the leveling instrument which is used to make the line of sight horizontal. The vertical distances are measured with respect to this horizontal line of sight and are used to compute the difference in elevations of various points.
In this process of leveling the Tacheometer principal, is used to calculate the elevation point.
In here the line of sight is bent from the horizontal. It is widely used in the hilly areas as it gives accurate estimation.
The first step of any construction project is to initiate the surveying process.
A land survey helps in the purchase of land and construction in the right direction. It is not possible to measure the plot of new land without the help of the Land Survey as it might lead to inappropriate land measurements.
Thus surveying plays an important role to know the potentiality of the land.