The Technology Revolution and Budo：Drones, Virtual Reality, and the Future of Judo〇Takeru SATO 1, Takayuki YOKOYAMA 2, Keisuke MIYAKE 3, Tatsuya INADA 4
1 Faculty of Education, Kogakkan University

2 Sports Development Center, Setsunan University

3 School of Health and Sport Sciences, Chukyo University

4 Graduate student, Graduate School of Faculty ofEducation, Kogakkan University

Introduction
The term “multicopter” is a broad one encompassing “drone,” but in this paper both will be referred to collectively as“drones.” Due to the rapid pace of development in recent years, drones have been in the spotlight as a technology
with applications in various fields. Today’s Information and Communication Technology (ICT) environment isexperiencing dramatic changes in adapting to current trends. These drone technologies have also begun to be used in
the field of sports. Because drones are capable of filming from angles that used to be impossible with conventional
tools, in fast-paced sports such as snowboarding and freestyle BMX, unmanned vehicles can film athletes from thesky, and so they are used in various situations, with further developments expected in the future. Recently, drones
have been developed to such a level that athletes can communicate interactively with them, and the drones arecapable of automatically taking off or landing. Drones can track athletes automatically, keeping them in the frameowing to the evolution of gyro-stabilization technology. As a judo coach, I am especially interested in thepossibilities that drones have for my sport. Recently, in judo competitions, a new system with a single referee has
been implemented. A single chief referee is in the contest area supported by two assistant referees outside of it. These
assistants help the chief referee to make decisions by either monitoring the competition directly or by inspecting
footage of the competition shot by two separate fixed digital video cameras. According to Hironori Hayashi, aresearcher at Biwako Seikei Sport College, when evaluating a throw, differences in the viewing angles or levels ofreferees could produce different evaluations. This finding indicates that there are limitations in evaluations made fromfixed angles, and if we consider the smooth progression of the competition and appropriate evaluations of techniques
during a judo match, the necessity of capturing images with highly mobile cameras from more perspectives becomes
clear. Because the aforementioned drone technology can track an athlete automatically and allow referees to monitor
the competition from any line of sight, it is possible to judge a competition from more angles. However, until now,there have been no studies on the feasibility of using drone technology to film judo competitions.

PurposeThe present study aims to clarify the current status of drone technology in order to explore possibilities for using
drones that can film matches from more angles during judo competitions.

Methods
The drone used in the present study was a DJI Mavic Pro, which is a leading-edge drone system equipped with ahighly sophisticated compact flying camera. The actual flight time of this drone was measured both when it washovering and automatically tracking a target (a pedestrian in the present study). The measurement was conducteduntil the battery was discharged to 30% (BL = 30%) and 20% (BL = 20%) in order to preserve enough power toreturn safety to the base station. The wind speed and noise level generated by the Mavic Pro in an environmentsimilar to the ones found at judo competition were alsomeasured. The wind speed was measured at 90 cm above
DJI MAVIC PROthe floor with a Floureon GM816 digital wind meter
when the Mavic Pro was flying (at 4m, 3m, and 2m)

Sanwa Sound Level Meter

above the floor; the average wind speed was obtained foreach flight level. The noise level was measured at 130 cm

4m,3m,2m

above the floor using the Small Sound Level Meter(Sanwa Supply, Inc.) when the Mavic Pro was flying (at4m, 3m, and 2m) above the floor; the maximum noiseFloureon GM816
130cm
90cm

level (in dB) was obtained for each flight level (Fig. 1).
In order to provide a point of reference for the wind

Fig. 1 Measurement of sound level and wind speed

velocity and sound levels, the amounts during a judo
competition at a high school were measured.

Results
The actual flight times when the Mavic Pro was hovering were 18 m 20 s (until BL = 30 %) and 21 m 10 s (until BL= 20 %). When it was auto-tracking a target, the flight times were 17 m 27 s (until BL = 30 %) and 19 m 56 s (untilBL = 20 %). The (average) wind speed and (maximum) noise level of the Mavic Pro when it was flying at 4, 3, and2m above the floor were 2.2 m/s and 77.6 dB, 3.3 m/s and 79.3 dB, and 3.9 m/s and 83.2 dB, respectively. For judo
competitions, when we look at the sound level of an ordinary high school competition space, the highest values
measured were: 83.7 dB for the first measurement, 96.4 dB for the second one, and 81.0 dB for the third one. Also,the lowest sound levels recorded were: 59.6 dB for the first measurement,60.7 dB for the second one, and 61.4 dB for
the third one. In measurements of wind velocity, no wind was found (Table 1).
Table 1 Environment data in arena
Drone used in empty arena
Noise level（dB）
Wind speed（m/s）
Hovering altitude（m）
Maximum value Minimum value
Average
2.0
83.2
70.3
3.9
3.0
79.3
65.7
3.3
4.0
77.6
62.3
2.2

Actual competition at high school judo tournament (no drones)
Noise level（dB）
Wind speed（m/s）
Number of times
Maximum value Minimum value
AverageFirst time
83.7
59.6
0.0
Second time
96.460.70.0
Third time
81.0
61.4
0.0

*Values measured for 1 minute*Values measured for 1 minute

Conclusions
When we compare the highest measurements obtained for sound levels, the first and second measurement for a highschool competition space was clearly found to be higher than measurements taken while the drone was in use.
However, for the lowest measurements, the sound level measured in a high school competition space for judo waslower than the one found when using the drone. We can conclude from this that when there is a great deal ofexcitement at a judo competition, the noise will be at a greater level than that produced by the drone. Whenever adrone is used, it produces some wind, and in a judo competition space, where there is normally no wind, we have toexpect the production of intermittent wind. Although my research suggests the levels are so low that there would beno significant impact on competition, further research on these needs to be done.
1) Hironori Hayashi, Hirotaka Okada, Katsuyuki Masuchi, Yoshihisa Ishikawa, Takanori Ishii, Michito Sakamotoand Koji Komata: Study of factors affecting different opinions expressed by Judo referees and judges regarding
throwing techniques, Japan Society of Physical Education, Health and Sport Sciences, 55(2), 363-378, 2010.