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Upgrading Photogrammetric Instruments 
Patrick Wong, MA 
|.S.M. International Systemap Corp. 
Suite 777 - 650 Georgia Street, Vancouver, B.C. V6B 4N7 
Tel:(604) 684-3750 Fax:(604) 684-9750 
ABSTRACT 
Analog photogrammetric instruments can be upgraded by encoding/interfacing to CAD software. Encoding system designs include the 
utilization of rotary or linear encoders mounted on the photo or model coordinate axes. Typical interfacing technology utilize solid-state 
"cards" for popular PC-Compatible CPU's. CAD software system may have been created specially for digital mapping or adapted from 
generic off-the-shelf packages. 
A more radical approach is the full conversion to analytical operations. Such approach requires special mechanical engineering and 
computerized "plate control" system. A better integration with CAD software is also effected. 
The cost/benefit analysis however, may not justify the upgrading of a typical analog instrument any longer due to the availability of 
affordable digital image based systems. In any case, the demand for digital image products can never be supported by upgraded 
analog or analytical instruments. 
KEY WORDS 
Instrument encoding, calibration, digital mapping system, stereo superimposition. 
1.0 INTRODUCTION irreversible. Most of these designs retain nothing more than the 
viewing and the plate carrier sub-systems of the original 
Photogrammetric instruments based on the simulation (or ^ instrument. The "Space Rod" and other mechanism that were 
analog) principle have been in production for more than 45 used to maintain a parallax-free model are replaced with a servo- 
years. Many of the early models of these, so called analog motor driven system controlled by analytical photogrammetry 
instruments, are still in use world-wide despite the advent of ^ software. 
the analytical plotter and digital image workstations. 
Instruments that are still in active duties include WILD A7, A8, 
A10, AMU/H, B8, AG1; ZEISS D2/3, E2/3; JENA 
Stereometrograph & Topocart models; Kern PG2 and some 
Santoni models. 
A more conservative approach in analog instrument up-grading 
may include instrument encoding, viewing systems modification 
and graphic system interfacing. ISM concentrates on providing a 
"turn-key" service in this approach. 
This paper will report ISM's experience in the field and provide 
some recommendations based on those experiences. This paper 
will also offer some of our insights as to the future of analog 
instrument upgrading. 
In the late 1970's it was apparent that Analytical Plotters and 
digital mapping were to be the way of the future. Many 
manufacturers offered retrofit systems for the existing late model 
instruments so that digital mapping could be performed. All of 
these "up-grades" included some form of instrument encoding with 2.0 GENERAL CONSIDERATIONS IN INSTRUMENT UP- 
an interface device connected to a computerized graphic system. GRADING 
For example, WILD offered the Synercom-Infomap interface, 
ZEISS offered the Intergraph IGDS interface and KERN offered ISM realized from the outset that digital systems are "unforgiving". 
the PC-PRO interface. Imperfections in the instruments (instrument errors) are brutally 
: revealed in numerical form. It is therefore extremely important that 
y early 1980s however, fne major manufacturers had ali but Users should understand that an instrument in good repair is 
horn fom upgrading analog instrument nd Wee necessary to support a digital conversion. |SM has also learned 
concentrating their efforts on Analytical Plotters. Despite the lack that many instruments were instaled in less than ideal 
of support from the major manufacturers, a thriving after-market ments with little or no maintenance. In order to avoid 
instrument up-grading industry developed. SM. International ing instrument errors with software algorithm problems, ISM 
Systemap Corp. (ISM), amongst others, offers such services. always offered, and occassionally insisted on a full instrument 
One approach to up-grading is a full "analytical" conversion of the service and calibration performed along with the up-grading. 
Instrument. This approach is more radical in that the process is Many late model analog instruments were factory encoded 
because the instruments were intended for "digital" aerial 
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