184 THE CANADIAN SURVEYOR May, 1960
TABLE III
Orienta- Maximum error prior Systematic parabolic my, of
tion to adjustment, m deformations per model | orienta-
Photo- | Length | points |. ton
graphs | of strip per points
model in in in at photo
X y 3 scale [azimuth | height scale
Aviogon
1:60,000 | 200 km 15 —110 | —240 +160 0.109/. 0.2627 210-179 /7 5| 359.0n
Aviogon
1:40,000 | 170 km 9 —130 | —. 40 =. 70 10.1377. | 0.04%/00 10.072 [eo | 23.34
| |
included. With the basic IBM-650, up to 500 ground control and tie points can be
adjusted. The location of the ground control points is arbitrary.
Adjustments of theoretical and practical blocks of strips show most encouraging
results. For instance, a block composed of nine parallel strips, each consisting of about
30 photographs made at the scale of 1:40,000, was triangulated on a Wild A-7 and
adjusted by the procedure described above. The size of the area involved is 60 X 70 km.
In the adjustment 26 ground control points, located mostly along the periphery of the
block, were used. Table IV shows the results. The computation time amounted to
TABLE IV
| Mean errors Maximum errors
|
x y x y
Ground control points +5 3m +4.4 m 11.4m | 10.4 m
Strip tie points +3 8m +3 5m | 10.2 m | 10.0 m
about 30 minutes. When the proper iteration sequence is used the computation con-
verges very rapidly and only very few iterations are required,
The Jerie horizontal block adjustment has undergone extensive testing by mapping
departments and it has been used in the adjustment of some blocks.
Use oF AERIAL T'RIANGULATION IN LARGE-SCALE PHOTOGRAMMETRY
In large-scale mapping the conventional aerial triangulation procedures are often
used. ‘This type of work is carried out mostly by commercial organizations. In con-
nection with the growing necessity to apply photogrammetry in legal survey problems,
this type of aerial triangulation is gaining rapidly in importance, and one may soon
expect a shift of research activities into this field.
EXTENT OF AERIAL TRIANGULATION Activity IN CANADA
Table V gives some information about the extent of aerial triangulation work being
performed in Canada during the four-year period. These figures are incomplete
since they refer only to the activities of federal mapping agencies. Some of the
provinces are in possession of quite impressive photogrammetric facilities (for instance,
British Columbia) but there are also several large photogrammetric commercial com-
panies that are able to handle large mapping projects, including aerial triangulation.
Some of them are particularly advanced in the use of the radar profile technique.
