ar
Cu
Fig.2 Photograph of the copper lion at door of Summer Palace
In order to meet the requirement for high precise
determination of automobile shell, a spiral blade
is accurately tested by refitted 19/1318.
The accuracy of survey point in industrial photo-
grammetry, for instance the automobile shell, is
highly required to reach 0.1-0.2mm. For this
reason, a high accurate control field in the
object space should be established, which is
determined by ratio method. Setting and levelling
two subtense bars on the object space, the
coordinates of control points and two end points
of subtense bar are measured by the forward
intersection with the approximate base. The ratio
factor is resolved from the coordinates of two end
points of subtense bar:
A =AB/V(XZ-Xp) 2+ (Y, -Y3) 2 (6)
where AB,the known length of subtense bar; X4, Y,,
Xe. Yg,the aproximate coordinates of two end
points. Then the correct coordinates of other
points are calculated:.
X=)\X', Ys AY' (7)
The length of second subtense bar can be got from
the calculated correct coordinates of end points,
equalling 2000.034mm. Comparing it with its known
length, 2000.000mm, the difference is obtained,
amounting 0.034mm. It is obvious that the accuracy
of this measuring method is good to close range
control because it is without the error of
distance survey and the influence of error of the
angle survey on points is not great due to the
close range.
The test blade, placing in the center of control
field of object space, is photographed by 19/1318
applying washer No. C. the average photographic
distance is about 2.5m.
The coordinates of object points are determined by
the space resection of photogrammetry from the
measured coordinates of ten or more control
points, in which the coorrection of lens
distortion is considered. Thus the photogrammetric
coordinates of sixteen points on blade are
obtained. The blade is immediately measured using
the machine for three-dimensional measurement
(LAMBOA 5606 from Italy), in which the precision
of point measurement come up to 6um, in the die
factory of the Second Automobile Manufacturer in
China. Taking the immediate measuring coordinates
as the pseudo-true value and comparing they with
the photogrammetric coordinates, the relative
standard error achieves to t0.118mm. The accuracy
is sufficient for requirement of determination of
automobile shell.
5 CONCLUSION
Originally, is the phototheodolite 19/1318 mainly
adaptable to the topographic survey, and now, is
it fully applicable to the close range photogram-
metry above one meter after refitted. The.
refitting method presented in paper is simple to
work, easy to process and convenient to operate,
and not destroies the former instrumental
construction. The satisfactory results was
produced through the product application many
times. The way of relying upon the old apparatus
instead of the new ones could save the import
funds. It is recommendable for the developping
country like China.
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