Analytical aerial triangulation is widely computed on electronic digital computers up to the block adjustment stage. Various possibilities for an analytical block adjustment are under consideration and one such method has been programmed at the Ordnance Survey of Great Britain. This paper briefly describes this adjustment and the trials so far conducted upon it. The trials suggest considerable economy without loss of accuracy when compared with the Jerie Analogue Computer at present in use.
An analytical relative orientation of a stereo-pair of photographs was computed in an unusual system of co-ordinates. The disparity in the widely mismatched photographs, their tilts and narrow angles subtended resulted in a rather weak solution from which sections of the lunar surface have been plotted. The results were not good but were better than expected. The main outcome of the work is a, probably unique, demonstration of the versatility of analytical photogrammetry.OBJECTIVE PHOTOGRAMMETRIC approaches to the problem of relative heights on the surface of the moon have not hitherto been able to improve upon those produced from shadow measurements. These latter, however, give a purely local relationship without much indication of the extension of the surface over large areas. The small librations of the moon combined with the distance from it of earth-based telescopic cameras (the "flying height") have made normal stereoscopic observations almost impracticable (Arthur, 1961).The Lunar Orbiter satellites have produced stereoscopic cover of parts of the surface, but as a preliminary to work upon this photography it was considered that Ranger photography provided the first opportunity to improve upon the stereoscopic conditions. A stereo-pair comprising one frame from the B Camera of Ranger VII and a part of a corresponding plate from Mt. Wilson Observatory gave a good angle of intersection of homologous rays, even though in many other respects some unusual problems were presented.The proposal was to obtain relative heights, and from these sections, over as large an area as possible, for further application in selenological investigations.
PHOTOGRAPHYThe Mt. Wilson camera has an effective focal length of about 120 feet; however, the enlargement factor of the diapositive used was not known precisely and the principal distance (P.D.) had to be determined from image points and subtended angles. A series of measurements gave a value of 77.6 m. 5 1 m. There is an uncertainty of 1 cm. or so in the position of the principal point but this was not considered serious with such a long P.D. The plate was exposed on 15th September, 1919.
The author has been involved in aerial triangulation, in various capacities, for some 27 years. This period has seen some very significant changes worthy of remark. This essay is a general review of that period; it does not go into detail and no formulae are quoted. The idea has been to look at the more notable developments, skipping the earlier and well documented period in favour of more recent times, particularly as regards the references. The objective will have been achieved if it provides a starting point, indicating further reading, for those who wish to study the subject in greater depth.
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