1. Fundamentals of Geodesy
Height Systems
Eng. Petya Dimitrova, Dept. of Surveying and Geomatics, BAU

2. Orthometric Heights
Discussed astronomic coordinates  and  give the position of a point on an equipotential surface
To define position in 3D space a third coordinate is needed:
In direction orthogonal to the level surface
It gives the height of the level surface above or below the geoid
The third coordinate is called orthometric height
Eng. Petya Dimitrova, Dept. of Surveying and Geomatics, BAU

3. Orthometric Heights
Orthometric height is the distance between the geoid and the level surface trough the point, measured along the plumb line.
It is known that:
Let dr point upward along the plumb line:
Eng. Petya Dimitrova, Dept. of Surveying and Geomatics, BAU

4. Orthometric Heights
Definition of orthometric height in terms of potential difference and gravity:
The gravity cannot be measured inside the Earth’s body:
Different approximations of gravity between the geoid and the Earth surface are used:
Different height systems are possible
Eng. Petya Dimitrova, Dept. of Surveying and Geomatics, BAU

5. Geopotential numbers Geopotential number C:
The gravity potential difference between the geoid and the level surface of the point
Orthometric height and Geopotential number
Eng. Petya Dimitrova, Dept. of Surveying and Geomatics, BAU

6. Dynamic Heights Dynamic height :
A constant gravity value is used instead of the real gravity:
is normal gravity at sea level at latitude 45o
Eng. Petya Dimitrova, Dept. of Surveying and Geomatics, BAU

7. Important Notes Points, which lie in the same level surface have:
The same Geopotential numbers; W1=W2
The same Dynamic heights:
Different orthometric heights!!!
Eng. Petya Dimitrova, Dept. of Surveying and Geomatics, BAU

8. Is it possible?
Eng. Petya Dimitrova, Dept. of Surveying and Geomatics, BAU