Maps and survey . 2. Quadripod beacon for Boundary. Phot. by Capt. E. M. Jack, TOPOGRAPHICAL SURVEY 141 caused by errors in this setting up and centering. To avoidthese difficulties an excellent form of self-centering beacon hasbeen introduced by the Survey of Egypt. The beacon consistsof a concrete pillar carrying on top a brass casting with threeradial V-shaped grooves planed at 120° apart. The threelevelling screws of the theodolite base, or the three feet of thehelio, stand in these grooves. The instrument can be put uponly in one position, which is automatica
Maps and survey . 2. Quadripod beacon for Boundary. Phot. by Capt. E. M. Jack, TOPOGRAPHICAL SURVEY 141 caused by errors in this setting up and centering. To avoidthese difficulties an excellent form of self-centering beacon hasbeen introduced by the Survey of Egypt. The beacon consistsof a concrete pillar carrying on top a brass casting with threeradial V-shaped grooves planed at 120° apart. The threelevelling screws of the theodolite base, or the three feet of thehelio, stand in these grooves. The instrument can be put uponly in one position, which is automatically the correct one, andno error of centering is possible. When the station is not in usethe pillar is covered over and the usual way. Thisself-centering device seems to be worthy of general adoption. Beaconing. The selection of sites for the beacons is done by areconnaissance party making a plane table sketch well aheadof triangulation party, and erecting the beacons on the pointswhich make the best
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Keywords: ., bookcentury1900, bookdecade1910, booksubjectsurveying, bookyear19
