- 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.