- 57 - 
iding control over 
akes it possible to 
ction of the storage 
rtments in use at the 
method, and the nu- 
k of reasonable size 
>er permits us to per- 
ata handling and wi- 
he computer pro - 
ipe, de la chambre 
photography is de - 
¡ts of : (a) Relative 
3 ; (b) determination 
■iplet assembly ; and, 
■es adjustment re - 
1 point employed in 
justed point coordi- 
with a linear three 
bitrary system to 
dinate transforma - 
1604 electronic 
ctitious photography 
ror Causes in 
ihotographs are 
t can be obtained from 
were accuratelydeter- 
ques, à least squares 
s performed several 
times at the Wild A7 Autograph, one triangulation by the method of aerial levelling using sta- 
toscope data, and the others by the method of aerial polygons. 
Comparisons were then made of the orientation elements as recorded at the A7, and 
the elements as determined by the analytical absolute orientation. The resulting graphs of ele 
ment errors versus position in the strip show : 
(1) True error propagation of each of the elements 
(2) True determination errors of each element 
(3) Close correspondence in successive relative errors for the several triangulations in each 
orientation element 
(4) The points at which " breaks " occur in the error propagation, permitting analysis of their 
cause or causes. 
(Note : an analytical triangulation may also be included in the above analysis). 
J.W. HALBROOK 
Measured Airbase Aerotriangulation 
Test results are discussed of a completely airborne system for establishment of a 
block of congruent stereomodels. The system utilizes a Tellurometer, aerial cameras, Air 
borne Profile Recorders, a stereoplotter, stereo-templets, and specially designed automatic 
scale adjusters. 
H. M, KARARA 
Theoretical determination of the maximum bridging distance in aerotriangulation 
projects 
To ensure a specified level of accuracy in aerotriangulated control (photogrammetric 
control) on which the stereoplotting of individual stereomodels is based, the bridged distances 
have to be confined within certain limits. This paper discusses the theoretical determination of 
the minimum density of ground control as a function of the required accuracy and the photo - 
grammetric system used. The basic idea lies in studying the propagation of errors in each of 
the steps involved in aerotriangulation and its adjustment. The propagation of the residual er 
rors (in planimetry and in elevation) remaining after the adjustment could thus be deduced. By 
restricting the bridging, distances to certain limits, the residual errors could be confined wi 
thin the allowable tolerances. Charts and formulae for the determination of the maximum brid 
ging distance as well as the theoretically expected accuracy in aerotriangulated elevations are 
derived and discussed. The planning and design of aerotriangulation projects could be made 
considerably easier and safer with the help of the presented charts and/or formulae. Thus, the 
designer of such projects is virtually free of the necessity of heavily relying on long experience 
and/or guess work. 
La détermination théorique de la densité minimum des points d'appui en fonction de la 
précision désirée 
Afin d'atteindre un niveau de précision spécifié pour un projet d'aérotriangulation, les 
distances entre les groupes de points d'appui pour les bandes doivent être limitées à certaines 
longueurs. Cette présentation traite le sujet de la détermination théorique de la densité mini 
mum des points d'appui en fonction de la précision désirée. Cette détermination théorique est 
basée sur des études détaillées des erreurs dans chaque étape d'opération et de compensation 
de l'aérotriangulation. Pour limiter les erreurs résiduelles à un niveau désiré, on doit limiter 
les longueurs des portées de la bande photographique ; c'est-à-dire, en cas de bandes longues, 
on doit fournir des groupes de points d'appui dont les distances doivent être déterminées à prio 
ri.