© 3D
vertical
horizontal
Fige3 Distribution of photogrammetric controls
required as input for the IMT, the measurement
of six grid points/stereomodel was carried out
in two projective planes by intersection method.
During the IMT, a simultane spatial transforma-
tion was executed for every models of the strip
where the computational units were the formerly
relative-oriented models with their projective
center's data. The observations to be adjusted
were the model coordinates, The model and plot-
ting scale were set up 1/2000 and 1/1500, res-
pectively. All computations were performed on
the IBM 370/158 computer of the THD, The total
CPU time was 38s for execution of the projec-
tive center computation and for the IMT run in
OS-HASP environment at 320 Kbytes virtual me-
mory size, The adjusted control, bridge points
as far as the baseline points and sections in
20 metres interval were drawn by electronic
flatbed plotter at scale 1/1500 serving orien-
tation control for on-line plotting operated
by the Wild A-lo autographe
Data acquisition
Setting up every single model, after the rela-
tive and absolute orientation the following se-
lective and adaptive sampling techniques were
chosen for the surface representation:
a/ Features as railroads, roads, bridges and
boundaries of the band of interest, Number of
registred points = 326, Digitized output data -
Lo le
b/ Grid points. Inside the band of interest a
semi grid system was established. The inter-
val in y direction was chosen constant lo met-
res while in x direction the operator has made
registration in time-interval carefully with
the aspiration that a smoothing curve on the
registred points on the real surface profile
in the same vertical plane be within an accept-
able interval of 1/3 metre, Number of regist-
red points = 1736, Digitized output data = X,
Y,2 /fige 4/o
42
grid model
1
step direction
Fige4 Grid model
c/ ICES profile points in sections, followed
the preliminary drawn lines perpendicular to
the predefined baseline with profiloscope.
Interval was set up to 20 metres while
density within the individual sections was
variable according to surface characteristics.
Handled as randomly distributed reference points
grid pattern generator program can process this
kind of data if desired, computing heights in
given intervals with one of the method reviewed
by Schut [5]. For this purpose a modified IBM
software is at our disposal which uses second
degree equation, in which the rightmost terms
are rejected according to the number and location
of the surrounding height references, The ave-
rage number of points/section «17, is conform
with the recommendation of the Swedish Road
Administration for normal and partially rough
type of terrain [1,4]. Number of scanned points
= 1119, Digitized output data = station no., X,
Yon / fige: 5/5
All points were registred by Wild EK-8 unit
interfaced with IBM 545 puncher on card media,
The disadvantage of this configuration is the
relative low registration speed and, at higher
recording density & large volume of output cards
would result; for mass recording only mag tape
is practical. For further representation of
the terrain based on string format storage
concept, reference points located on contours
as characteristic terrain features were regist-
red. Vertical interval of contours at 1/2000
model scale was 2 metres, in some cases with
additional intermediate information. The num-
ber of contour points registred in time-inter-
val = 1260, The standard error both in plani-
metric and elevation sense was less than ,1
in 1/1000 of the flying height,
