The role of digital components in photogrammetric instrumentations

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Monograph

Persistent identifier:: 830281363

Title:: The role of digital components in photogrammetric instrumentations

Sub title:: symposium of Torino, Italy ; 2nd - 4th October 1974

Scope:: ca. 200 Seiten in getrennter Zählung

Year of publication:: 1974

Place of publication:: Torino, Italy

Publisher of the original:: [Verlag nicht ermittelbar]

Identifier (digital):: 830281363

Illustration:: Illustrationen, Diagramme

Signature of the source:: T 15 B 1280

Language:: English

Additional Notes:: Literaturangaben

Other Title:: Nebentitel: Digital components in photogrammetric devices

Usage licence:: Attribution 4.0 International (CC BY 4.0)

Corporations:: International Society for Photogrammetry, Commission, 2

Adapter:: International Society for Photogrammetry, Commission, 2

Founder of work:: International Society for Photogrammetry, Commission, 2

Other corporate:: International Society for Photogrammetry, Commission, 2

Publisher of the digital copy:: Technische Informationsbibliothek Hannover

Place of publication of the digital copy:: Hannover

Year of publication of the original:: 2015

Document type:: Monograph

Collection:: Earth sciences

Chapter

Title:: TRENDS IN DESIGN OF DIGITAL EQUIPMENT FOR PHOTOGRAMMETRIC INSTRUMENTS. U. V. Helava

Document type:: Monograph

Structure type:: Chapter

Coordinate Recorders Most, if not all coordinate recorders on the market today, are based on a straightforward system design shown as a block diagram in Figure 1. Encoder pulses are accumulated in UP/DOWN counters, or alternatively the measured data is obtained in an absolute code. In either case, a sequencer or a multiplexer scans the counters and presents their contents one by one to transmission logic, which interfaces with the recording device. Point identification numbers and display devices are usually added; however, they are accommodated with the same design approach. A somewhat more advanced design is shown in Figure 2. Here the counters are replaced by an adder and a memory. A multiplexer or a se quencer looks at all input lines frequently enough to be able to pick up all pulses that arrive. These are then added to coordinate values in appropriate memory locations. The transmission of the data to the re cording device is from the memory. Even a very rudimentary memory can provide useful buffering and a basis for relatively simple addition of various arithmetic functions. A microprocessor is capable of integrating all functions needed to drive the recording device from encoders; see Figure 3. Encoder pulses cause interrupts which in turn cause incrementing or decrementing of "counters”. Physically, the counters are internal registers or memory locations whose contents are manipulated by the program of the micropro cessor. Shift of origin, scaling, and other simple arithmetic functions can be readily implemented. Means for communication with the recording device are available as a standard feature. Microprocessors can be used with minimum additional hardware to function as specialized system components, as was the case just explained. On the other hand, they may be expanded to become microcomputers. [14] The microprocessor is employed as the CPU of the computer and its per formance is boosted by additional memory, input/output channels, interrupt lines, etc. Figure 4 shows a recording system based on a microcomputer. The most reasonable place for it is probably at or in the recording de vice. The presence of a microcomputer permits great flexibility in re cording format, as well as some editing, data analysis, and further pro cessing, e.g., coordinate transformation. The trends that may be observed in the evolution represented by the examples described above, are quite typical. The trend is from specific to general, from hardwired to firmware and to software implementation, and in terms of performance from bare bones to considerable flexibility. Physically, there may be a trend that is not typical: the processing is moving toward the recorder. This is contrary to the general trend of distributed processing which tends to put processing power closer to the data source; encoders in this case. However, if the recording system is considered as a part of the entire photogrammetric process, it becomes quite clear that the general trend is valid also in this case.

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