THE TRIANGULATION OF CULTIVATION OVERLOOKED BY HIGH GROUND |
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| Abstract: | Abstract14. General. Except for one or two located by an auxiliary triangle or by ray and distance, every point is fixed by a fully observed triangle of which the base is a pair of pillars. To justify the larger and more expensive party required for this method a high rate of observation must be maintained. The two observing periods available each day in the northern Sudan are the 3–4 hours starting just before dawn, and the 2–3 hours which end with sunset. Since moveluent in the cultivation is generally slow and on foot or by donkey, the longer morning period is best used for observing the single angles at each of a series of points there. The shorter and hotter afternoon period may then be used for observing the rounds of angles at each of a pair of pillars, which can normally be reached or at least approached by car. Asfar as possible the points observed to from these pillars will be those occupied on either the preceding or following morning, so that the triangles can be closed as soon as possible. Up to nine triangles have been closed in a day. |
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