The main observation is that even with poor accuracy of
auxiliary data (t 10 m) very interesting results for the
block accuracy are obtained (n, - 2-0, PM, T 3s0, ), be-
ing directly sufficient for small scale mapping (in
1: 60 000 photo scale 0, corresponds to 0,9 m in the
terrain). The same accuracy could be obtained without
auxiliary data only with bridging distances of 8 base-
lengths (case C5/E0). With camera position accuracy of
about 3 m the resulting accuracies of the terrain point
coordinates X, Y, are in the order of O9. 1“ 8, equival-
ent to very dense ground control per model. (It should
be remarked that the measuring accuracy in height is
equivalent to o,, ” C, J2°h/b = 2.4 00; with 6, = 15 um,
fy, = 35 um, a rather poor value.)
With the optimistic acceptance that all exterior
orientation elements could be measured with high accura-
cíes (t. 0,l m for Xp Yoo! Z»c and t 0,7 mgon for
Q, ¢,K ) by navigation systems , one would obtain
very high accuracy for the adjusted block with values of
pare 0.6 * v, and p, = 0,. In this case, the block ad-
justment reach an accuracy level, where only the photo-
grammetric measurements determine the limit. This is
confirmed by the theoretical limit case for error free
navigation data (PO).
3.2 Ground control
A comparison of the values in table 2 referring to the
cases © E1/C0, ° EL/C1 and E1/C2 demonstrates, that an
additional ground control does not lead to: Any
significant improvement of the adjusted block accuracy
(Fig. 3). rIt-is obvious that aerial triangulation does
not require ground control if all six exterior orient-
ation elements are availabe as auxiliary data. (This
conclusion might slightly be modified if drift para-
meters are to be determined as well.) In cases where
only the camera position coordinates or only the
attitude parameters are observed, additional ground
control is necessary to stabilize the block. Also the
case CO (without ground control) is not realistic as the
datum problem is not solved. Therefore some control
points are required for transforming the block into the
state coordinate system. The case Cl (4 control points)
may represent the practical case of minimum control.
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