* Industry: Dell Foster, Baush & Lomb, Auto Trol, Bunker, Ramo,
Bendix, Wild, Zeiss Oberkochen, Zeiss Jena, Galileo, OMI,
Matra/SFOM, SOPELEM , Kern, etc.;
Universities and institutes: University of New Brunswick, NRC Canada,
Ohio State University, ITC , etc.;
* Other institutions: USAETL, USGS, Hansa Luftbild, Ordnance Survey, etc.
The A/D interfaces can be differentiated from the viewpoint of:
— operational characteristics, i.e. into stationary and dynamic (9), (10); 4
— compatibility with different instrument types, computers or recording e e
devices;
— components and their configurations (11);
— programming facilities (e.g. hardwired ROM's, PROM's, etc.);
— other features (e.g. reliability, maintainability, etc.);
D/A interfaces are needed for digital control of mechanical movements
in real- or nearly real-time environment. A strict real-time operation is
required in dynamic mode with feedback control (i.e. in the case of servo-
mechanisms). In dynamic operation with sequential control and in stationary
operation the control need not be strictly real-time, which relaxes the
requirements.
From the operational point of view manual overriding of digital control
should be possible, i.e. the motors should be disconnected (de-coupled) for
fine and/or eccentric settings. Moreover, when reaching model- or other pre-
determined boundaries, the motors should stop.
III-3 Digital computer
A photogrammetric instrument may be supported by a general purpose e -
tabletop-computer, a minicomputer or a (special purpose) microcomputer
(12), (13), (14). The supporting computer can be linked with another more
powerful computer which is the case in multiple systems (Chapter V). The
computer supporting a photogrammetric instrument, should meet certain
basic requirements. Often it is desirable to have the main storage expandable
(e.g. to 8K or 16K) and/or a bulk storage connected. The basic routines
should be callable from a keyboard and the input and output devices should
operate fast enough. Compatibility with different peripheral units is essential.
