The role of digital components in photogrammetric instrumentations

Bibliographic data

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

11 A comparison of Figures 5 and 8 might suggest that we have progressed in a circle. In both cases the servo loop is closed inside a computer. However, in reality the common trends are again verified: the trend has been from specific to general, and the presence of a microprocessor in the servo- system is a good example of distributed processing. Analytical Plotters When discussing here the design trends in analytical plotters there is no reason to start with a historical perspective. Much of what was said previously about recording systems and servos applies to input and output functions of analytical plotters as their development has progressed over the years. Let us therefore start from the present. Figure 9 shows a typical design approach that may be applied to analytical plotters today. All minicomputers in the class capable of handling the analytical plotter requirements have an I/O bus. Peripheral equipments communicate with the computer via this bus, to which they are connected by a bus interface. The bus ipterface contains all the necessary timing and control functions to establish the communication link, as well as pertinent address and data transfer contacts. The input and output functions of an analytical plotter can be tied to the computer by interfacing to its I/O bus. Fig ure 9 shows schematically what is involved. Essentially, there is a trade-off between the number of bus interface units employed and the amount of additional control logic. A practical and cost-effective com promise in most cases is to use several bus interface units, as shown in the figure. Microprocessors are inherently capable of performing various logic functions required in interfacing with the computer I/O bus, and with other devices. Specifically, they can multiplex data in and out, and between these functions also perform data accumulation or "metering out" for servos. Figure 10 shows a possible design approach suitable for the relatively slow microprocessors readily available today. The ever-increasing speed of microprocessors leads to another design concept that may in the near future become feasible. As shown in Fig ure 11, all input/output functions are channelled through a single micro processor. Obviously, in line of what was said about distributed pro cessing and servos, the input and servo channels may include dedicated microprocessors of their own, as means of implementing necessary logic functions. Finally, the computer may become a microcomputer, as shown in Fig ure 12. It may seem again that we have progressed in a circle. This is not so: the system of Figure 12 is a distributed processing system with a hierarchy of processors. Such a concept is certainly intellec tually pleasing; its significance, however, is in equal measure based on practicality. All the microprocessors may be identical, differing

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