Authors presented field test results of the ship motion in the survey boat SUO, which is a catamaran, obtained in irregular waves KOKURA in KYUSHU Island on January 1973.
　When the test was carried out, she was light draft without devices for survey work.
　Test speeds were 5 kts, 8 kts, and 12 kts, that were near the planned survey speeds.
　The test results were as follows.
　Rolling angles decreased with each increment of speed and the average rolling angles were about 1.6 degrees at 5 kts, 1.4 degrees at 8 kts, 1.0 degrees at 11.2 kts.
　The average pitching angles were nearly constant at all speeds, however the maximum angle gradually increased with the speeds.
　The cross-correlation between rolling and pitching was not over 0.3.
　The sounding error was mainly caused by rolling, and it decreased with the speed.
　However, at times it was over 30 cm even at 12 kts.
　The sounding error caused by the average rolling angle were around 10 cm and those values were within the accuracy of the device.
　The positioning error reslted from the ship motion were within the accuracy of her electric positioning equipment.
　Judging from test results, SUO would have the suitable ability a survey boat, when she is light draft.