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Probably the fact that the Netherlands itself is flat and that the inner orientation has about
no influence in the case of flat terrain has stimulated a method without regular calibration
of the cameras.
Contrary to the calibration of the cameras, all services report regular checks on the
adjustment of their restitution machines. K.L.M. Aerocarto mentions that this check
takes place at least once a year. The Survey Department of the Ministry of Transport and
Waterstaat reports regular tests, generally 6 times a year or at any time when there is a
reason for control.
The instruments in use for aerial triangulation in space are only the universal plotters
Wild Autograph A 5 and À 7 and the Zeiss Stereoplanigraph C 8.
For all photogrammetric triangulation in the Netherlands itself no use is made of any
auxiliary instrument, not even a statoscope. Here again the flat terrain and the rather
short strips in case of triangulation in space will have influenced this policy. K.L.M. Aero-
carto is equiped with an airborne profil recorder which is in use for contracts abroad.
The most important application of this device was on the aerial survey of the southern
half of Suriname (Ia + I b in tabel no. 4) on an area of 55.000 square kilometers with
only 7 astro points of which 4 were along the northern border of the area. The entire
height control was provided by airborne profil recorder, starting at one barometric base
station at the northern boundary of the area.
Regarding the method of orientation, this is in general in all services the same. An
approximate relative orientation is obtained with the optical mechanical method of Von
Gruber and completed by the numerical method measuring y-parallaxes in six points.
K.L.M. Aerocarto reports that in a few cases where residual parallaxes are too high or
high precision is required, 9 points are used for the computation of the elements of relative
orientation.
A further remark is that after the instalment of the instruments in the new Delft buildings
for I. T.C., Survey Department of Rijkswaterstaat and for K.L.M. Aerocarto, aircondi-
tioning was used for temperature (20-21 degree Celsius) and for relative humidity
(60-65%).
Commission III has divided the statistics of actual production in two different parts
namely strip triangulation and block triangulation. I believe that this will be, in several
cases, misleading since there is in practice a difference between the triangulation of isolated
strips and the triangulation of strips, forming together a block, even when no block adjust-
ment is applied. Also in such cases, where only strip adjustments are computed there will
be a possibility for lateral comparison of the adjusted coordinates of the common points,
which gives at least a check. Consequently there will be a possibility to apply corrections
for jumps in scale and azimuth, with the result that this method of computation comes
close to the primitive pre-war block adjustment method. We would have in such blocks
real strip adjustment only if each second strip were adjusted, with the only possibility to
evaluate the precision of the obtained adjusted coordinates during the plotting of the
models of the intermediate strip. I found that this fairly inaccurate method is still in use
in some countries,
It would have been desirable to distinguish between:
a. triangulation of isolated strips;
b. strip triangulation without any block adjustment, taking the mean value of coor-
dinates of common points in two adjacent strips;
c. triangulation of blocks with application of block adjustment (analytical least squares
adjustment, I. T.C. — Jerie Analogue Computers, interpolation method of Zeller, or
pre-war adjustment by lateral comparison as published in 1940 by the author).
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