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Stadiametric rangefinding, or the stadia method, is a technique of measuring distances with a telescopic instrument.The term stadia comes from a Greek unit of length Stadion (equal to 600 Greek feet, pous) which was the typical length of a sports stadium of the time.
The stadion (plural stadia, Ancient Greek: στάδιον; [1] latinized as stadium), also anglicized as stade, was an ancient Greek unit of length, consisting of 600 Ancient Greek feet . Its exact length is unknown today; historians estimate it at between 150 m and 210 m.
For example, a typical stadia mark pair are set so that the ratio is 100. If one observes a vertical length on a stadia rod, rule or levelling rod with the telescope and sees that the rod spans 0.500 m between the marks (the stadia interval), then the horizontal distance from the instrument to the rod is: 0.500m x 100 = 50 m.
2 stadia 369.9 m (404.5 yd) double pipe hippikon ἱππικόν: 4 stadia 739.7 m (808.9 yd) length of a hippodrome [5] milion μίλιον: 8 stadia 1.479 km (1,617 yd) Roman mile: dolichos [4] δόλιχος: 12 stadia 2.219 km (1.379 mi) long race parasanges, or league [6] παρασάγγης: 30 stadia 5.548 km (3.447 mi) adopted from ...
A stadimeter operator adjusts the lower knob until the top and bottom of the object are aligned, and then reads the corresponding range off the edge of the lower knob through a small magnifying lens. A stadimeter is an optical device for estimating the range to an object of known height by measuring the angle between the top and bottom of the ...
The tenths of a foot point is indicated by the top of the long mark with the upward sloped end. The point halfway between tenths of a foot marks is indicated by the bottom of a medium length black mark with a downward sloped end. Each mark or space is approximately 3mm, yielding roughly the same accuracy as the metric rod.
The perimeter of a stadium is calculated by the formula = (+) where a is the length of the straight sides and r is the radius of the semicircles. With the same parameters, the area of the stadium is A = π r 2 + 2 r a = r ( π r + 2 a ) {\displaystyle A=\pi r^{2}+2ra=r(\pi r+2a)} .
Wild brand subtense bar. Another device used in tacheometry to measure distance between the measuring station and a desired point is the subtense bar. [2] This is a rigid rod, usually of a material insensitive to change in temperature such as invar, of fixed length (typically 2 metres (6.6 ft)).