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Aviation History
1958
1958 - 0204.PDF
214 economic operation, for civil use. The advantages of flying higher,now that much improved camera lenses and finer grain film permit the use of smaller photographic scales, will be apparent. Photo-graphy at 40,000ft above ground requires only one-quarter the number of photographs now needed to cover a given area at20,000ft. An alternative approach may be the development of a survey camera lens possessing all the advantages of high resolu-tion and low distortion of the present 6in focal length lens, but with a focal length of 3yin on the same format of 9in x 9in.The camera to carry this ultra-wide-angle lens is promised for 1959; and since, in theory, the effect will be almost to halve thephotographic scale for a given flying height, the same economy in number of photographs required will follow. Possible dis-advantages of such a lens would be the occurrence of "dead ground" when areas of high relief and the extremities of thephotograph coincide, and an associated danger of reduction in FLIGHT, 14 February 1958 Two Wild RC5a fully automatic vertical cameras installed in a Swiss- owned Hunting Survey Prince. The nearer camera carries a film maga- zine, while the other is adapted for Jin x Tin plates. photographic quality when the more obliquely inclined incidentrays pass through a layer of atmospheric or smoke haze. With regard to progress in external aids, notably in aircraftposition-fixing, simultaneous development in electronic methods for ground measurement should not be overlooked. These havegreatly speeded up field-survey operations and it should be remem- bered that some areas scheduled for development require notonly maps but also a framework of fixed ground-points on which the engineer may base his more detailed surveys. If ground con-trol operations can be expedited sufficiently then it may be better to provide an initial ground framework which will be of valueboth for small-scale topographical air survey and subsequently for the engineer. Finally, it is interesting to note the increasing use made of airsurvey as an aid in cadastral survey and the recording of rights to land. This is a comparatively recent development which islikely to progress rapidly in the light of increasing social con- sciousness among the populations of countries now movingtowards independence. Satisfaction of a demand for title to a plot of land has considerable political significance, but the regis-tration of such title automatically involves survey if a land problem h not to be initiated for future generations. Land survey staffsin many of the countries affected are inadequate for the purpose, and authorities in these territories, which are usually withoutadequate large-scale maps, have turned to air survey as an alterna- tive. In general, it is not economic for such air-survey operationsto be undertaken on a local basis and much work both of an experimental and productive character has been done by Britishcommercial air survey companies during the past five years. It must be emphasized that the air survey method cannot produceall that is required and that it is almost impossible to avoid limited ground survey both for final emplacement of permanent boundarybeacons and for survey in areas of dense vegetation. Nevertheless, sufficient has been done to show that the shortage of ground sur-veyors should not impede progress in this vital operation and one may look forward to continued development both in the use ofthe aerial photograph by itself, as a record of topographical detail, and of the map produced from it in a stereo-plotting machine asa basis for cadastral survey. W. P. S. s u r V ——e y CAMERAS AND PLOTTING MACHINES EVER greater precision is the constant goal in the develop-ment of the whole range of instruments used to record andreproduce ground features for mapping. Quality and per- formance of the lenses, film, plates, shutters, printers, enlargersand plotters has already improved to such an extent that new equipment is being designed to eliminate those errors which wereearlier thought to be relatively unimportant. Infra-red and colour are being increasingly used for the study of soils and forest, andinfra-red offers additional advantages in penetrating haze when extremely wide-angle lenses are used from great heights. The latestaddition to the series of Wild cameras is to be the super-wide- angle RC9 with a focal length of 88 mm (3.5in). Angular field willbe 120 deg, picture size 9in x 9in and lens distortion not greater than 0.01 mm. The need for ground control is being significantly reduced,especially when Shoran and combined radar and barometric height-finding devices have been fitted, as described in the fore-going section of this review. The special radar altimeter in these operations is the Airborne Profile Recorder made by PhotographicSurvey Corporation, Toronto. It is a narrow-beam pulse radar, coupled with a barometric altimeter and synchronized with avertical-positioning camera, producing a graph of aircraft and ground height togedier with a series of positioning photographs.It is accurate to between ± 10ft and ± 20ft, depending on condi- tions; and it can either establish control points for mapping ordelineate ground profiles for such projects as roads or power-trans- mission lines. The aerial dish measures 44in across and altitudelimits are between 1,000ft and 35,OOOft. Fairey Air Surveys have themselves developed a statoscopewhich will sense with extreme accuracy any vertical displacement of the aircraft from a given barometric height. It is used to checkthe scale of air photography. The principal camera manufacturers in the world are Williamson(Britain), Wild (Switzerland), Zeiss (Germany), Fairchild (U.S.A.), and Nistri (Italy). Many of the cameras produced for civil usehave direct military equivalents; and those which become sur-
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