Unto KORHONEN 
Aerial triangulation in the Finnish Cadastral Survey 
Aerial photographs have been used in Finland for large cadastral surveys c : a 10 
years, and the aerial triangulation has proved to give sufficiently accurate results in most of 
the cases. The cadastral survey is carried out by the National Board of Survey and its District 
Survey Offices. 
Before the photographic, flight (h = 2, 3 km, camera = RMK A 15/23) white targets are 
set on the geodetic points and the boundary marks. In forested areas the targets have to be e - 
rected up to 15 meters above ground. The aerial triangulation is made by a Zeiss C8 Stereo- 
planigraph, the coordinates being recorded with Ecomat-device and punched directly on cards. 
Conformal 3rd degree formulas are used for coordinate transformations. These are program 
med for Elliott 803 and the IBM-computers, 1620 and 1410. In the IBM-programmes provision 
is made for automatic elimination of rough errors. The accuracy has proved to be 40 microns 
in the scale of photographs (radial error). The cost is found to be c : a 5% of the total mapping 
cost, that amounts to 10-12 marks/hectare on the average. 
The aerial triangulations made up to now are instrumental. The analytical methods ha 
ve been investigated and tested and the practical applications will be undertaken in the imme 
diate future. 
FRANCE 
Institut Géographique National 
Etat actuel de l'aérotriangulation analytique (Cf. Bulletin n° 15) 
Institut Géographique National 
Application des mesures photogrammétriques à la géodésie tri-dimensionnelle 
(Cf. n° 15) 
GRANDE - BRETAGNE 
J. A. WEIGHTMAN 
Mathematics of Space Triangulation 
A - Analytical rectification of a single photograph 
1 - Reconstructing camera-directed direction cosines from photo-coordinates (corrections for 
lens distortion, IMC during exposure,etc) 
2 - Converting to space-directed direction cosines (corrections for refraction, aircraft motion 
during exposure,etc) 
3 - Deriving space cartesian coordinates at an assumed elevation (conversion to other coordi 
nate systems) 
B - Simultaneous adjustment of a number of photographs 
1 - Obtaining provisional space cartesian coordinates as above 
2 - Evaluating distortions of this provisional space framework from the ideal internal camera 
geometry (reconstructed from photo-coordinates) and from the geometry of known ground con 
trol points 
3 - Forming observation equations to reduce these distortions by varying the space cartesian 
coordinates, camera positions and orientations (additional observation equations for auxiliary