The Analytical Orientation of a Lunar Model

Abstract

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.

Some Considerations Regarding Mapping From Earth Satellites

“…Both Mr. Petrie in his remarks tonight and Doyle (1971) in his Otto von Gruber Memorial Lecture have criticised the rather inferior cameras used in satellites; both have expressed their gratification that at last we are going to see the use of cameras in which the photogrammetrist has had some say. I would like to quote an earlier paper of my own (Proctor, 1968) describing the use of some Ranger 7 photography. This was a hard landing (crash) lunar probe which, therefore, had to send back television photographs before impact; the camera was fitted with a reseau but I had to point out that neither the camera lens nor the reseau had been calibrated before despatch.…”

“…Mr. Petrie: Could 1 start answering by asking a question of Mr. Proctor? We know from his paper in the Record (Proctor, 1968) that he worked on the Ranger photography, but 1 understand that he, later, also worked on the Lunar Orbiter material. I wonder if he could say something about the results of his experience with this for, as far as I know, the results have not been published in the Record and it would be interesting to hear what the difficulties were.…”