The mats used in judo are called Tatami. Tatamis are traditionally 0.9x1.8m, and made of rice straws. Today, the tatamis are usually either 1x1, 1x1.5 or 1x2m, and made of compressed foam.
there are 2 competitors
one referee
and 2 other referees, sitting on a chair at two of the corners of the mats, to help support the main referee when awarding ippon/waz-ari/yukoand shido(penalty...