According to the key data provided by the International Amateur Athletic Federation for the 400m standard track and field, the diameter of the field is 84.39m, and the arc radius at both ends is 36.5m. See Figure 1.
Fig.1 Schematic drawing of inner ring ditch measurement
Therefore, there are two key control numbers when measuring the centerline of the inner ring ditch, one is a straight line with a length of 84.39m, the other is a radius of 36.5m with a circular arc, and the radius of the general design is 36.0m.
400m inner ring ditch measurement line, the ring ditch center line shall prevail. For the measurement, the axis of the center of the site is used as a reference as shown in Figure 1. Theodolite support at O1, rear view O2, corner 90. (Vertical), from the radius of the O1 ring groove, at the corner 90. A point in the direction. At the same time, reverse the mirror (or turn 90., back to 0. Then turn 90.) from the O1 ring groove radius, in the direction of the line of sight, B, move the theodolite O2 point, also came to C and D, connecting AD and BC Get the centerline of the straight part of the ring groove. Theodolites are at 15 o'clock and 2 o'clock respectively. The angle is a direction. Measure the length of the ring groove in the direction line, that is, the 13 points in the center of the inner ring groove are obtained respectively. From the point A connected to the point B, half an inner ring groove curve is obtained. Similarly, Connect point C to point D to get another half of the inner ring groove curve.
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