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>Measuring - how to spot correctly

Measuring - how to spot correctly

based on an article by Manuel Schütz in Swiss Boomerang Newsletter 2/2004

A description of the basic measuring procedure can be found here. The additional notes in this article are intended to help improve the distance measurement in terms of speed and accuracy.

In addition to or out of the roughly 6 to 10 range spotters on the field, there is one head spotter or \"runner\", who places himself at the point of farthest flight distance projected onto the ground. He signals the head / measuring offical at the baseline that agreement has been found on the farthest point and the distance to the bullseye can be measured (preferably with a laser range finder). During the distance finding process, i.e. the \"discussion\" phase, he coordinates the measurements of the individual spotters to establish the \"best estimate\" for maximum distance. Therefore, the head spotter should be a person with experience in LD spotting, only then reliable measurements of maximum accuracy can be obtained.


  1. The spotters take the bearings of the apex of the flightpath and mark an imaginary point on the ground or further away (tree, bush, etc.) in the direction of the measurement.

    Fig. 1

  2. The head spotter chooses the spotters HE thinks got the most accurate measurement (that would be spotters A and B in Figure 1). First, he finds the imaginary measuring line of spotter A (he is directed by spotter A). Then, he moves along this line until he intersects with the measuring line of spotter B. If there are more than two spotters with a useful measurement, the head spotter has to judge the significance of the measurements, based on the sideways angle to the apex (90° is ideal), distance to the side (0 m: bad, 20-40 m: ok, then decreasing significance), direction of the sun, and experience of the spotter.
  3. The head spotter can also use his own judgement, should he have been positioned well enough for a reliable measurement. That is up to him to decide.

    Fig. 2

    The second duty of the head spotter is to communicate with the head official at the baseline (preferably with walkie-talkie) and notify the spotters in case of an invalid throw, so that they do not have to hold their imaginary measurement line any longer.

  4. Avoid:

  5. The walking direction of the head spotter depicted in Figure 3 is wrong ! He has to remain on the measurement line of spotter A, even though spotter B is directing him forward. The head spotter can help making his process of distance finding transparent by letting the spotters know what he is doing at the moment (if this should not be obvious..).

    Fig. 3

    The measurement of spotters C and D can be used to confirm the result. In any case, the head spotter is not to be influenced by spotters claiming that they \"have seen the apex very precisely\" if they are obviously not well positioned. The word of the head spotter is final.

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