7 
III. 2. 2 Determination of altitudes. 
Different altimetry methods can be applied to perform specific functions 
Absolute altitude and scale over m. s. 1. 
Altitude differences between exposure stations. 
Terrain profile or spot elevations 
Performance of the elements. 
Element Description 
number 
ALT 1 Static air pressure measurement from static 
vent pick-off in flight. 
ALT 2 Barometric air pressure lapse rate per flight 
height, in unknown non-standard atmosphere, 
influence at medium-scale flight altitude. 
ALT 3 Local barometric air pressure reduced to mean 
sea level according to standard atmosphere 
(QNH). 
ALT 4 Local air temperature lapse rate per flight 
height, measured each 20 mb. 
ALT 5 Isobaric surface sloping, without corrections 
being applied, over distances longer than 100 km. 
ALT 6 Mean isobaric surface after slope corrections, 
obtained from height control at both ends of the 
flight line. 
ALT 7 Mean isobaric surface after slope corrections 
obtained from wind and latitude according to 
Henry. 
ALT 8 Residual isobaric undulations about the mean 
ALT 9 Statoscope with individual photograph recording, 
instrumental and system error at high altitude 
(6000 m) 
ALT 10 Statoscope, same system as above, at low 
altitude (1500 - 2000 m) 
ALT 11 Hypsometer with continuous recording and 
continuous strip photo positioning, at high 
altitude. 
ALT 12 Hypsometer, same system, at low altitude. 
ALT 13 Radar, direct APR radar distance or height 
measurement, cm radar type. 
ALT 14 Laser, direct distance or height measurement, 
50 MC type 
Random errors in 
meters height 
0.5 m 
approx. 200 m 
approx. 1 m 
approx. 3 m 
not exactly known 
approx. 1 m 
0.5...1 m 
0. 5... 2 m 
2 m 
0. 7 m 
1.5 m 
0.6 m 
0.10 
0.001