Surveying ME - BMEEOAFM201

Definitions

• mean sea level
• reduced level
• relative heights in a building

Measurement methods

1. levelling (optical, hydrostatic)
2. trigonometrical height measurement
3. physical methods
   

Levelling

In case of levelling a tangential line (or plane) of the equipotential surface is created by a suitable instrument. The instrument is called the surveyors’ level.

Principle of leveling

hydrostatic (based on the principle of communicating vessels)

optical:

Reading on the leveling staff: Reading1, reading2, reading3, reading4

Getting the height difference: $\Delta h_12= h_1-h_2$

Type of levels

• tilting level
• automatic level

Major error sources - way of elimination

• collimation error - adjust your instrument on a regular basis
  
• tilting of the staff - use circulare bubble on the staff
  
• atmospheric effects - avoid strong sunshine, instable atmosphere
• settlement of the staff - use change plate
  

Aim of levelling: determine (1) new control points or (2) detail points.

Levelling methods

• line levelling

• long and cross sectional levelling

• grid levelling

• detail point levelling

Trigonometric heighting

Principle, figure and formula

$RL_P=RL_A+IH+ \Delta h-TH$

where

$\Delta h= \frac{HD}{tan(z)}$

or

$\Delta h=SD \cdot cos(z)$

Advantages and disadvantages compared to levelling

Measurement of the height of buildings using trigonometric heighting

Barometer for height measurement

Read the Bohr's story