There is another laser system that has been prepared for very precise geodesy. This system, referred to as the Spaceborne Geodynamics Ranging System (SGRS). would employ a single satellite in a circular orbit of 100-km altitude and 50° inclination (Smith, 1978). Aboard the satellite would be a laser-ranging system that would be directed in rapid succession toward up to several hundred ground-based retroreflectors distributed over regions of interest. Computer simulations indicate that accuracies in relative positioning on the order of 1 cm (0.03 ft) or better can be expected from a 6-day mission for stations separated by up to 300 km (about 200 miles). The report from the Workshop on the Spaceborne Geodynamics Ranging System (1979) recommended that study of the approach be continued with the goal of implementing an actual demonstration in conjunction with the Space Shuttle at the “earliest possible date.”
The technological developments described above do not change the fundamental concepts and principles laid out in this report. Rather, their impact will be on the costs of the various alternative procedures for building a multipurpose cadastre. Their effect will be to increase the feasibility of a cadastral records system.
Because of’ economic considerations, most of the satellite systems considered would be applicable mainly to the establishment of primary geodetic nets and would not displace densification by photogrammetric. inertial, or conventional traverse methods. A possible exception would be a system having capabilities comparable with those projected for the GPS. If the system could successfully operate amid the obstacles of an urban environment, it would suffice to have a single base station at a convenient point in each county operating in conjunction with any number of mobile units operated by private surveyors performing routine surveys. Alternatively. in difficult areas one could envision a GPS system used in conjunction with a compact (second- or third-generation) inertial system, the former providing nearby temporary control for the latter.
The foregoing considerations make it clear that emerging technology will be of increasing, and ultimately dominant, importance in the establishment of the multipurpose cadastre. A rational program for widespread implementation of the cadastre concept must accord due weight to such developments. Some jurisdictions need to improve their system of ground control now. They cannot wait for the new technology. The costs of survey-related projects in the short term and the uncertain pace of technological development make investment in improved ground control by traditional methods a wise one. Jurisdictions that will have significant growth in the near future and jurisdictions with particularly poor systems of existing control are candidates for investment now. Whether investment occurs now or in the future, however, there should be adherence to the basic principles of a geodetic reference framework—large-scale base maps and a cadastral overlay.