Surveying Interview Questions and Answers

Surveying is the art of determining the relative positions of point on, above or beneath the surface of the earth by means of direct or indirect measurements of distance, elevation, and direction.

The best surveyor is not the one who is extremely accurate in all his work, but the one who does it accurately enough for the purpose without waste of time or money.

1. Determining relative positions of various points, above, on or below the surface of earth,
2. To mark the positions of proposed structure on ground.
3. To determine areas, volume and other related quantities.

There are two major principles of surveying,

1. Working from whole to part – first a system of control points is fixed with higher precision for a large area. Minor control points can then be established by less precise methods within the main area. It prevents accumulation of errors. Minor errors are localized in this system.
2. Location of a point by measurement from two points of reference.

To determine the level, staff is kept inverted at the staff station and negative foresight is noted.

Least count of the measuring instrument is the least graduation marked on the instrument below which the instrument cannot measure.

Representation factor is the ratio of distance on the map to the distance on the ground i.e., R.F = Distance on the map/distance on the ground.

In this, 1:100 scale is larger because accuracy of map is high.

The book in which chain or tape measurements are recorded is known as field book. Standard dimension of book is 20 cm x 21 cm, double line field book is most commonly used for ordinary survey works.

Base Line –  is a long survey line which is run through the middle of the area to be surveyed. The frame work of triangles is built upon the base line.

Check Lines – lines run to check the accuracy of the main frame work of triangles. Also called proof lines.

Chain of length 100 feet having 100 links is called Engineer’s chain.

Bearing of line is the angle between a meridian and a survey line or we can say that a bearing is the clockwise or anticlockwise angle between north or south and a direction

Bearing measured from one station to adjacent next station in the direction of traverse/surveying is known as fore bearing and bearing measured from one station to adjacent previous stations in the opposite direction to traverse/ surveying is called back bearing.

Declination is just an angle which is in between the magnetic north and true north. Whereas magnetic dip is an angle between magnetic field lines and a horizontal plane at a particular location on the planet.

Traverse survey is a method in the field of surveying to establish control networks. It involves a number of connected survey lines and form a frame work.

If a closed traverse is plotted according to the field measurements, the end point of traverse will not coincide exactly with the starting point, owing to the errors in the field measurements of angles and distances. Such an error is known as closing error.

Levelling is a process of determining the height of one level relative to another. It is used in surveying to establish the elevation of a point relative to a datum, or to establish a point at a given elevation relative to a datum.

Datum – datum is an imaginary level surface or level line from which the vertical distances of different points are measured or we can say that any surface to which elevations are referred.

Reduced Level (R.L) – height or depth of a point above or below the assumed datum is called R.L.

Benchmark – B.M is fixed reference point of known elevation.

1. Backsight – sight taken on a known elevations, to obtain the height of instruments (known as plus sight)
2. Intermediate Sight – intermediate between two points on which only one sight (minus sight) is taken to determine the elevation of the station.
3. Fore Sight – taken on unknown elevation. (Known as minus sight)

1. Height of instrument method
2. Rise and Fall method

The surveying in which both horizontal and vertical control can be achieved i.e., horizontal and vertical distances of various points can be determined directly with the used of instrument. This is a fast method and error will not exceed 1/1000.

A contour may be defined as an imaginary line passing through the points of equal elevation. Since a contour map is a three-dimensional representation of the earth surface, it furnishes a lot of information i.e.,

1. Determination of inter-visibility.
2. Character of terrain,
3. Site selection
4. Drainage area
5. Capacity of reservoir etc.,

Plane tabling is a graphical method of survey in which the field observations and plotting processes simultaneously. It is essentially a tropical instrument and not intended for very accurate work.

Total station is an electronic theodolite integrated with an electronic distance meter (EDM) to read slope distances and elevations from the instrument to a particular point.

1. Total stations are mainly used by land surveyors and civil engineers either to record features as in topographic surveying or to set out features such as roads, houses, boundaries etc.
2. Total stations are also used by archaeologists to record excavations.
3. Meteorologists also used total stations to track weather balloons for determining upper-level winds.
4. Total stations are also used to record the absolute location of the tunnel wells, ceilings and floors of an underground mining.

It reduces the error due to line of sight.

1. Theodolite
2. Sextant
3. Clinometer

Survey is done from whole to part so that if large main frame is precisely established consisting of widely spaced control points, their subsidiary small frameworks can be established with less accuracy thereby confining the errors in a localized region and avoiding accumulation of errors.

It is an instrument used for setting out right angles in fields.

Determining the bed depth of a water body in order to have a bed profile is called as sounding i.e., measurement of bed depth below the water surface.

To mark the positions of the stations or terminal points of a survey line.

The ranging rods are almost invisible beyond the distance of 200 meters that’s why we use coloured flags to increase the visibility of rods.

At the zero end or rear end and is called follower.

The levelling staff determines the amount by which the station is above or below the line of sight.

1. Barometric levelling
2. Trigonometric levelling
3. Spirit levelling

Height of instrument method is more rapid, less tedious and simple, a number of reading can be taken by the same instrument setting. Whereas rise and fall method is more tedious, needs time for full check of calculations for all sights.

Refraction, earth’s curvature, variation in temperature, settlement of tripod on turning point, wind vibrations are some of the natural errors occurred in levelling.

The branch of surveying which deals with the measurements of bodies of water is known as hydrographic surveying. It is the art of delineating the submarine levels, contours and features of seas, gulfs, rivers and lakes.

In geodetic surveying the curvature of earth is considered in plane surveying and the ground is considered plane.

3 satellites

Control points are the points on the field whose location (latitude, longitude and height with respect to MSL) is known with greater accuracy. In survey purpose of establishing control points first is to minimize errors. Control points are established using the most precise instruments for collection of data and rigorous methods of analysis.

With the help of trigonometric levelling.

The least count of a levelling staff is 5 mm.

A plump bob is a device in which a weight usually with pointed tip on the bottom, suspended from a string by using law of gravity in establishing a vertical reference line or plumb line.

Fundamental principles of surveying are

1. Measuring distances from two fixed point
2. Working from whole to part

Before a highway alignment is finalized in highway project, the engineering survey are to be carried out in following stages: –

1. Map Study – Alignments are drawn on available maps considering maximum utilization and avoiding obstructions.
2. Reconnaissance – it is done by visiting at site location for detailing of features which are not available in map (ex. Temples, low forest areas, power grid etc.)
3. Preliminary Survey – This survey is carried out to collect all the physical information which are necessary in connection with the proposed highway alignment. Topographical survey, traverse, levelling work, drainage study, traffic study, chain survey, compass survey, soil investigation are included in this stage of survey. Highway alignment is finalized in this stage.
4. Detailed Survey – After preliminary survey, detailed survey should be carried out for collecting the information necessary for the preparation of plan and construction details for the highway project. The data during detailed survey should be elaborate for preparing detailed plans, material, cost estimation and design etc. of the project.