e. o 
16 
where: 
ns. = standard (longitudinal navigation) error 
mg, = standard (longitudinal) error of unit weight 
(flight time 1 hr) 
The value for mg _ can be expected to be: ! 
S 
Nt 20600 WU o © 
It seems that for a given survey application, — i.e. operation of one particular 
INS system in one particular aeroplane, flying in one particular country . 
(gravitation anomalies), and one type of survey (manoeuvres) — the system 
performance can be improved by in-flight calibration of the systematic 
influences. 
4B.2 Fokker integrated F-27 systems 
The four systems — delivered to Iran — have partly been calibrated in- 
flight by comparing the absolute orientation elements actually obtained, with 
those recorded at each photograph. 
The fifth system — delivered to Algeria — is being calibrated now by the 
combination Fokker/ITC/Meetkundige Dienst van de Nederlandse Rijkswater- 
staat/Institut National de Cartographie/Forces Aériennes algériennes. 
The first results have made it obvious that the attitude sensing (i.e. 
verticality) is not only recorded with a resolution of 0.5 minutes of arc but 
that the actual recordings have an extremely high accuracy comparable to the 
accuracy of the highest precision photogrammetric instruments. e - 
The relative position of the photographs are supplied with a resolution : 
of 60 ft. 
The autopilot/F-27 system maintaines altitude within 15 ft. (one sigma). 
The heading variations have proven to be about 0.4 degrees. 
1) Performance test for spraying applications have been carried out by the Government 
of Quebec. The flight pattern — as compared to other tests — is most similar to these 
flown in aerial survey. See Ref. 6.1.