Safety | Measure | Plans | Airfoils | Materials | Flight path | Smith | National Records | WR Evolution | Mailing list | Syndicate
Home | Forum | Results | Articles | FAQ | Competition archive | Media Gallery | Store
News
-LD in Bordeaux
-Maulbronn 2016
-Swiss LD Championship 2016
-US Nationals

 
 

Measuring - how to spot correctly
Nov 30, 2005, 16:59

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.

Procedure:


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


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.
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.

Avoid:

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.
 
 
 
© 2005 BAGGRESSiVE

Measuring
Sep 17, 2007, 12:34

Download the LD template here:
http://www.baggressive.com/downloads/LDScoreSheet.pdf

We want to ensure that LD competitions follow the same rules all over the planet now and for all. Here you will find guidlines how to organize and run an LD tournament properly. We arevery much interested in helping you to hold a well organized and accurate LD tournament. Contact us at ld@baggressive.comif you require assistance. Always keep in mind:
  • LD is the most dangerous boomerang event ! Be serious about this and brief the competitors accordingly. Send spectators sufficiently far away ! Read our safety advice carefully.
  • You will need at least 10 people to hold a proper tournament, because you need at least 6 spotters on the field to measure the distance of the boomerangs.
  • Boomerangs do not need to be caught upon their return.
  • Metallic LD boomerangs are not allowed in tournaments due to safety regulations.
  • Paint your boomerangs with a bright neon color to facilitate spotting it in the air and finding it on the ground.
You do not need a lot of stuff to organize an LD tournament. You need a baseline of 40m length, made out of a rope or a ribbon, and a circle at the center with a radius of 2 m, i.e. a standard bullseye used in bomerang tournaments (marked with ribbon, chalk or paint). The end of the baseline is marked with a post on each side. The baseline is usually perpendicular to the wind direction. However, the thrower may have it rotated around the center as he wishes.


For the throw to be valid, at least one foot of the thrower has to be on the ground inside the center half circle at the moment of release of the boomerang, and the thrower must NOT crossthe line at any time as long as the boom is in the air. The boomerang has to cross the baseline upon return, either directly or from behind, otherwise the throw is not valid (cf. drawing with valid / not valid boomerang flightpaths).

Officials & Spotters

The head official's place is near the throwing circle. He runs the tournament. He calls forth the throwers, ensures correct throwing from the center circle, and communicates with the head spotter on the field. There may be another official helping him in his task. In addition, there are two line judges at the left and right end of the baseline, respectively, to judge whether the boomerang crosses the line or is out of bounds.

Thereis a number of spotters on the field to determine the farthest point of the boomerang's flightpath. We suggest the spotter arrangement shown in the schematic on the left. You have to be aware that if the boomerang is more or less flying over you, it is difficult for you to judge where the projected path on the ground actually is. Only by spotting from a distance off to the side are you able to determine the apex of the flightpath accurately. Therefore, we suggest placing a row of spotters to the left and right ofthe expected throwing corridor, respectively, with a ~20m distance between the spotters within one row. You can also align the two rows in a a staggered manner to get a better coverage. The spotters should be spread such that all throws, including the shortest and farthest ones, can be precisely spotted. Send the farthest spotter sufficiently far out, as there may always be "lucky" throws. One of the head spotter's duties is to ensure that the spotters are distributed correctly.

Don't use more spotters than necessary to fulfil the task, because with too many spotters they tend to walk about and have chats ! 6 is the minimum (+1 head spotter), 12 should be enough in all cases. Here's what you have to do as a spotter: Follow the boomerang on its way out with your extended arm and stop when you think it reached its farthest point. Then project that point down onto the ground by lowering your arm vertically. Fix the point on the ground with your eyes and direct the head spotter to that point. At least one other spotter will do the same, so the head spotter will have to position himself such that the closest 2-4 spotters are happy with the result. Often, there is a little arguing about the farthest point, but that's the interesting part of spotting: discuss until there is agreement ! The spotters that could not see the apex of the flightpath very well should not interfere ! The maximum distance of the boomerang is now defined as the distance from the head spotter to the center of the throwing circle. If you have a Laser Rangefinder (e.g. a Bushnell) you can measure the distance immediately, otherwise you have to place a marker in the ground and measure the distance at the end of the round with a (steel !) tape.

We estimate the accuracy of the measurement with this "spotting" method is 2m in the best case, 5m on average, and more if the spotters are not placed very well or if they are not paying attention. It is actually helpful to distribute thin wooden sticks (~2m long) to the spotters, with the help of which it is much easier to follow the flying boomerang at its farthest point and drop the perpendicular to the ground.

© 2005 BAGGRESSiVE
www.baggressive.com provides information for boomerang throwers and interested parties. You'll find all the info you need to successfully throw a boomerang over 100m and have it return over your head.
Sponsors: Renegade Motorhome - Costa Rica - Guitar Lessons - British Virgin Islands