What are the characteristics of contour lines?

What are the characteristics of contour lines?

Characteristics of Contours

  • Must close on themselves, on or off the map.
  • Perpendicular to the direction of max.
  • Slope between them is assumed uniform.
  • The distance between them indicates the steepness of the slope, gentle or steep.
  • Irregular signify rough, smooth signify gradual slopes.
  • Concentric closed contours: hills or depression.

What are form lines?

: a line drawn on a map to depict surface configuration in a generalized manner and usually without indicating elevations — compare contour line.

What is the basic difference between contour line and form line?

Contours : A contour is an imaginary line (drawn on map) joining the points having the same elevation above the sea-level. Form Lines : These are broken lines. This method is used in association with contours to show the hilly or mountainous country. They are drawn without any precise measure units.

Is fall in line correct?

(idiomatic) To submit to the rules of a higher authority; obey; conform.

What does spot height mean?

A spot height is an exact point on a map with an elevation recorded beside it that represents its height above a given datum. In the UK this is the Ordnance Datum. In geoscience, it can be used for showing elevations on a map, alongside contours, bench marks, etc.

How do you find the height of a spot?

Spot Height = 11.500 – ((11.500 – 11.000) x (30 ÷ 60) drawing. We can use the method outlined previously.

What is the difference between spot height and benchmark?

The spot height can be defined as the height of the particular point on the ground that often explains the height of a hill or mountain. The spot height is measured from the main sea level. A benchmark can be used as a point of reference that is generally marled on stone.

What is a spot level in surveying?

Dumpy Level Survey. A dumpy level (also known as a Builder’s Level) is an optical instrument used to establish or check points in the same horizontal plane.

How do you calculate RL in surveying?

– method to calculate RL; height of collimation (H of C) = reduced level(R.L.) + backsight (B.S.) reduced level (R.L.) = height of collimation (H of C) – foresight (F.S.) reduced level (R.L.)

What is Rise and Fall method?

Rise and Fall Method is the method of calculating the difference in elevation between consecutive points in levelling work. Some of the points you have to know before starting numerical are: Back sights: The first reading after seeing the instrument is called back sights.

What is TBM level?

Temporary Bench Mark (TBM) – a point of known height above a pre-defined level. This level is not absolute and is defined locally by the surveyor for the purpose of the survey. The height of any target point is referred to as Reduced Level (RL), because it is reduced to a known datum.

What is GTS bench mark?

A G.T.S. (Great Trigonometrical Survey) benchmark is a permanently fixed reference survey station (or point), having known elevation with respect to a standard datum (mean sea level). These are established all over India by Survey of India department with greater precision.

How do you read a dumpy level?


  1. Set your tripod up near the spot you want to measure.
  2. Connect your device to the tripod and position it over 2 leveling screws.
  3. Level the device by adjusting the 2 leveling screws.
  4. Turn your telescope 90 degrees and adjust the third leveling screw.
  5. Check your level’s calibration by turning it 180 degrees.

What is HI in leveling?

Differential Leveling. Definitions. Height of instrument (HI) – the elevation of the line of. sight of the telescope. Starting point.

How do you calculate RL and hi?

Height of Instrument Method | Surveying and Levelling

  1. Height of the Instrument Method.
  2. Determine the RLs of various points if the reduced level (RL) of a point on which the first reading was taken is 136.440 gives the height of collimation method and applies the check.
  3. HL = RL + BS.
  4. Check.

What is Levelling formula?

If you know the elevation of A, called E(A), you can calculate the elevation of B, called E(B), as BS -FS + E(A). But BS + E(A) = HI, the height of the instrument or the elevation of the line of sight directed from the level.

How do you calculate backsight?

Measure a backsight on A (for example, BS = 1.89 m). Measure on C a foresight FS = 0.72 m. Calculate HI = BS + E(A) = 1.89 m + 100 m = 101.89 m. Find the elevation of turning point C as E(C ) = HI-FS = 101.89 m – 0.72 m = 101.17 m.

How do you calculate rise and fall level?

8 Rise and Fall Method This method consists in finding the difference of level between consecutive points by comparing each point after the first with that immediately preceding it. The reduced level (R.L.) is found by adding rise of subtracting fall to or from the preceding reduced level itself (R.L.).