On the other hand angular attitude errors in w or ¢ of
10 mgon cause maximum displacements in the projection of
rays of 38 pm in the photoscale, with wide-angle photo-
graphs. It means that the displacements will hardly exceed
0,1 mm at map scales of 1:10 000 or smaller, taking the
usual relations between photoscales and map-scales or ortho-
photomap-scales into account. It also means, that the re-
quirements also for large scale photomapping will be met,
if the orientation data would reach a precision of 0,5 m or
better in position and 5 mgon or better in attitude.
5.3 More detailed considerations have to distinguish bet-
ween mono-projection (rectification, orthoprojection) and
stereo-projection. It can be shown, and it is confirmed by
simulation, that the errors of attitude data and of positi-
on data, if set directly as image orientation elements, are
acting independently in first approximation.
We consider first the monoprojection of photographs, as
applied in rectification and orthoprojection. The error ef-
fects of directly set orientation elements on the projection
are summarized in the following table. It shows the r.m.s.
projection errors uxy, considering the net area (18 cm x
18cm) of à wide-ancie photograph (f = 15 cm), and assuming
standard errors of o,,4,c= Oa =10 mgon and o 2g
= 10 um of attitude 25 Position data, espe LA ches
latter converted to photo-scale.
combined effect
IX Sac 1:60 000 photo scale
10 mgon 10 mgon |og = 10 mgon, opc = 1m (= 17 um)
by y image area | 28 um 11 um 2,0m
Hy y edges 32 um 11 um 2 ,Q. i
by y corners 36 um 11 um 2,4 m
The values show that the assumed precision of the orienta-
tion data would, in this case, allow about 3 x enlargement
to the photomap. The error effects go proportional with the
precision values og and opc and thus can easily be trans-
ferred to other cases. The gaps between adjoining projec-
tions will be V2 times larger than the above values (y) for
edges and corners, respectively. The conclusion is that
direct setting of navigation data would be sufficient for
photo-mapping if attitude data would be precise in the order
of 1:10 000 (= 6,4 mgon) and position data, reduced to photo-
scale, in the order of 20 um. The latter specification is
equivalent to 1,2 m for 1:60 000 photo scale or to 0,4 m
for 1:20 000, respectively.
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