Page 58 - Ranger Demo

Computations and Results
While we were happy with our field calculations, the final adjustment was carried out back at Tolworth. Initially, our observations on the three loops showed closures of 1:142k, 188k and 263k, respectively. For the final adjustment ‘sticks’ of the old catenary traverses between azimuth stations and all of the early tellurometer traverses to the east of Georgetown were added. No Laplace observations were considered necessary.
The result showed only one significant unexplained anomaly, which was a 9-second difference of azimuth between DOS 16 and the nearest 12th Parallel point only two lines away. Nevertheless, the overall root mean square results were between one and two seconds (including the observed length equivalents) or 1 part in 138,000.
Conclusion
The project was unique and very much ‘of its time’. Serving multiple masters was non-trivial, sometimes frustrating, but satisfying. Working in two languages and with two currencies was often challenging, and the subtle differences in education and survey observing techniques between French and British systems was interesting. The observations were almost all conducted by the counterpart surveyors. The survey was also one of the last Bilby tower traverses before GNSS surveying became accurate and cost-effective enough to take over geodetic and then lower-order control surveys. The towers remained in the Gambia where at least one was purloined by a bird watcher in the British High Commission to get closer to his feathered friends!
Figure 12 Senegambia Connection
Hindsight
A web search shows that the Senegal-Gambian Secretariat still exists and now has a subsidiary boundary committee that always seems to have work to do! Our ancestors on both sides of the channel have a lot to answer for in the divisions of Africa, and it is only in 2019 that the river was finally bridged within the Gambia. Arguably this has benefitted Senegal much more than the Gambia by efficiently connecting the southern province of Casamance to the capital, Dakar. Many Gambians have lost jobs on ferries and the accompanying services for long queues of lorries!
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