How do you calculate RL?

– 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 the difference between RL and FFL?

Hello and welcome to Just Answer. I don’t see it that often but engineers and surveyors use R.L. for Relative Level or Reduced Level. It is a measurement of height taken from some known datum. F.F.L is First Floor Level.

Is AHD and RL the same?

These levels are referred to as “Reduced Levels” ( R.L. ) which means a height above (or below) a nominated datum. In Australia, this datum is called the “Australian Height Datum” ( A.H.D. ) and is the relative height of a point in relation to Australian mean sea level.

How do you take rl in a survey?


  1. Set up the leveling instrument at Level position 1.
  2. Hold the staff on the Datum ( RL +50 m) and take a reading.
  3. Move the staff to A and take a reading.
  4. Move the staff to B and take a reading.
  5. Move the staff to C and take a reading.
  6. Move the staff to D and take a reading.
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What do you mean by RL?

The term Reduced Level is denoted shortly by ‘ RL ‘. National survey departments of each country determines RL’s of significantly important locations or points. These points are called as permanent benchmarks and this survey process is known as Great Trigonometrical Surveying (GTS).

What is RL height?

Reduced level ( RL ): this is the height or elevation above the point adopted as the site datum for the purpose of establishing levels. To establish the required depths for a drainage system you need to work from the datum point. The datum is taken as a reduced level of 10,000.

What is the highest RL that the FFL can be?

Frequently on contract drawings (plans, sections and elevations), finished floor level may be abbreviated ‘ FFL 27,000’, the figure suffixed denoting the level in metres above a defined datum level (usually outside ground level or ground floor level). The floor above may be FFL 31,000 and the floor below FFL 23,000.

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.

What is FGL level?


How do you calculate AHD levels?

If you look on the footpath of recent developments in the area you will often see a rivet in the footpath which is either a relative level or a AHD point. If you can find a AHD point, and its value, you can then take points from this back to your property to find your own AHD levels.

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What does M AHD mean?

Australian Height Datum refers to the elevation (from the ground) of any object, relative to a reference point. In Australia this reference point is sea level which is taken as 0 metres AHD. All flood levels, floor levels and ground levels are provided in meters AHD.

What is mean sea level datum?

Mean Sea Level ( MSL ) is a tidal datum which is computed by the National Ocean Service (NOS), Center for Operational Oceanographic Products and Services (CO-OPS) as part of the National Tidal Datum Epoch (NTDE) based on data collected over a 19-year tide cycle.

Why RL is given?

Ringer’s lactate solution ( RL ), also known as sodium lactate solution and Hartmann’s solution, is a mixture of sodium chloride, sodium lactate, potassium chloride, and calcium chloride in water. It is used for replacing fluids and electrolytes in those who have low blood volume or low blood pressure.

How do you calculate RL from Rise and Fall?

Rise and Fall Method is the method of calculating the difference in elevation between consecutive points in levelling work. Arithmetic check:

  1. Last R.L – First R.L = 42.842 – 43.000 = -0.158 m.
  2. ∑B.S – ∑F.S = 7.561 – 7.719 = -0.158 m.
  3. ∑ Rise – ∑ Fall = 4.932 – 5.090 = -0.158 m.

How do you calculate RL by HI method?

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.

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