Another Multi-Band Camera for Archaeology

Photogrammetric Brief --~ JULIAN H. WHITTLESEY Whittlesey Foundation, Inc. Wilton, CT 06897 Another Multi-Band Camera for Archaeology FIG. 1. The 35-mm multi-band camera and The construction of a 35-mm gimbal system. mu Iti-band motorized and radio-controlled camera system is described. HE SUCCESS of our first aerial multi cameras on the market saved little weight T band camera (Whittlesey, 1972) has led over the Hasselblad EL 500 with Zeiss Dis to the design and construction of an entirely tagon lens. They were not a point of depar new one, in this case for 35-mm rather than ture in this case. Therefore, we had no choice 6-cm film. Both formats are needed in field but to design a system that would accept work. Motorized film advance and remote three standard hand-held 35-mm cameras radio control are obvious requirements and serve to operate them as a motorized where the camera platform is an unmanned unity. The very compact lightweight Rollei tethered balloon or airfoil high in the sky, or a 35 was chosen. It is equipped with a Zeiss floating tripod on the water at some distance Tessar 40 mm focal length lens affording an from the operator. These features are also a angle comparable to that of the Zeiss Dis great convenience even when the platform is tagon 50 mm focal length lens on the larger a bipod raising the camera 10 meters over a format. sensitive archaeological excavation (see Another reason for turning to 35-mm film Whittlesey, 1966). was the convenience to the archaeologist in No 6-cm format multi-band camera having his lectures, as opposed to the larger format been on the market in 1972, we designed and requiring big projectors or the inconvenience made our own as had ASA, Grumman of providing reductions for the more usual Ecosystems, the Defense Mapping Agency, smaller classroom projectors. Resolution of and perhaps others. Likewise, today there is 35-mm film will satisfy most archaeological no 35-mm automated, radio-controlled, missions, but the 6-cm format remains far pref multi-band camera on the market. The Has erable for photogrammetric plotting. The selblad EL 500, already automated, gave us a smaller film will be practical also for spectral head start on our first multi-band camera. analysis in most, though not all, cases. Each There was no such head start for the 35-mm format has its place in our work, which in version if it were to meet the foremost re cludes search missions, mapping, photo in quirement, namely, a material saving in terpretation, and general recording. A capac weight. One statement in the Photogrammet ity of three cameras such as for color, B & W ric Brief (Whittlesey, 1972) proved wrong. and IR, or for various filter combinations, suf The 23-pound camera system therein illus fices for most any mission. Two cameras in trated, along with gimbal, resulted in an un unison will do for many missions, and one favorably low Lift-over-Drag (LID) ratio will satisfy some. when flown by a tethered balloon manage The 35-mm multi-band system able by a two-man ground crew. A good LID motorized, radio-controlled, and carrying ratio is very precious to the balloonist. three cameras - is now completed (Figure Motorized radio-controlled stock 35-mm 1), rigorously tested, and ready for the next 731 732 PHOTOGRAMMETRIC ENGINEERING & REMOTE SENSING, 1975 field season in the air. It weighs in at one perfect flying weather. The solution for sure third the Hasselblad version above referred and timely release was to maintain the to, which came to 23pounds. Measuring but 7 shutter-release button depressed so that the by 13 by Jl/2 inches, it may be flown from the release takes place of itself just as the film same gimbal and below the same balloon advance is completed. Accordingly, each employed for the single Hasselblad EL 500, cycle of the operation stops a quarter-second which has been our most reliable mono short of having completed the film advance. camera on scores of aerial missions in many Once the signal is given the advance finishes, countries. The design, redesign, construc releasing shutters within the quarter second. tion, and reconstruction of the prototypes The return and next advance follow within leading up to the final successful result has seven seconds to await the next signal for taken many months. In the course ofthe work exposure. we set up our own precision shop under the A common drive shaft operates a pair of guidance ofMr. P. W. Winter, who has built a reduction gears at each camera to swing for variety of systems from our designs in the ward and to return the film-advance lever. past. Work on the new system started in his Ten miniature ball bearings seat the drive shop in ew York City and was completed in shaft and gears to tolerances within 0.001 ours. inch. Camera mountings are equally precise, As-built drawings and specifications have although they do not qualify this multi-band yet to catch up with the final work, but will be as a metric camera, as is the earlier Hassel available eventually. Meanwhile, the follow blad system. The film frames do not carry fidu ing description along with photos and wiring cial marks. diagram may satisfy those who are interested The drive shaft turns a commutator on in further detail at this time, The first design which five points are precisely located. Two decision was that the Rollei 35 be left intact of these govern polarity of the current for as taken from the shelf. We had learned some forward or reverse motor action. Two provide time ago not to build our own cameras or to mechanical stops to protect the cameras modify stock cameras except in minor re against over-run of either the advance or re spects. But two minor exceptions to this deci turn action. The fifth operates a limit switch, sion were made, namely that the film closing each cycle. Adjustment in the gearing advancing levers were inverted and shutter is tooth-by-tooth to assure perfect coordina release button maintained in the depressed ·position. tion·among cameras. Each camera is very precisely mounted in The heart of the electrical system (Figure the sturdy structural aluminum-channel 2) is a double-pole magnetic-latch relay. This .frame. A strobe light is also mounted as in the affords great versatility in the sequencing of former multi-band. Its distant flash from the the four circuits at its disposal. Only two cir sky assures the operator on the ground that cuits, however, are utilized: one is for the the radio signal has been received and motor and the "on" latch; the other is for the obeyed. A single 12-volt-D.C., geared elec "off' latch magnetic-relay receiving its signal tric motor advances and releases the cameras from the limit switch on a separate circuit. simultaneously. Themotor was built by Wer The "off' latch not only shuts off all current tronix Corporation to our performance but bY.its own action renders itselfdead. We specifications following torque tests of the call it the suicide relay. This precaution in cameras..Shutters release within a quarter the circuitry is vital to reassure resumption of second ofthe radio signal or, ifhand-held, of the action should any cycle close; leaving the the manual signal. Film advance and re limit switch engaged. The "on" latch, receiv cocking follow automatically upon the shut ing its signal from the radio or manual start, ter release, the cycle taking seven seconds, then will take precedence overthe"off' latch less if the voltage be increased. A blue light ·relay whose separate circuit had been left burns during the film advance, a red one dur open. We arrived at this circuitry only after a ing the return of the film advance lever. number of others had proven unreliable and These lights are helpful signals as the multi been dismantled. Manual and radio signals band is prepared for flight, and are well to are wired in parallel so that the multi-band watch during the initial ascent when some may be operated hand-held as shown in Fig low-level coverage may be taken. ure 3. Cameras are mounted with the view The mechanical design became simple finders unobstructed. after a variety of relatively complex shutter The electrical controls are recessed in the release systems was discarded. These had channel at one ep.d of the (rame. They are developed "hang-ups" not to be risked in protected by a transparent dust cover permit field work. One such can spoil the day of ting observation of the commutator, double- ANOTHER MULTI-BAND CAMERA FOR ARCHAEOLOGY 733 FIG. 2. Circuitry for the 35-mm multi-band camera. pole-stack reversing switch, magnetic-latch relay, wiring, and the miniature circuit lights associated. The larger colored circuit lights before mentioned are mounted in more evi dent positions within the frame. One-and one-halfvolt pen-light batteries are recessed in the side channels and are protected by covers. While other re-chargeable batteries are equally practical, these batteries are cho FIG. 3. The 35-mm multi-band camera sen as easily replaceable even in very remote shown being hand held. towns and villages in far countries. One set of eight alkalide 1.5-volt batteries suffices for over 100 cycles. An extra pair reinforces the camera-support systems for aerial, terrestrial, current to the very critical"off' latch-relay as and underwater recording.

Load more