Abstract
Automatic Radar Plotting Aids (ARPA) is one of the instruments effective for aiding safe navigation in term of collision avoidance and its informations are well utilized and highly appreciated among watch officers. But a few knowledge is available how a target position was decided from a radar echo signal (ARPA position) and ARPA information is based on the past ARPA positions of targets. This article assumed 4 different target positions as an ARPA position and we performed a Monte-Carlo analysis to find the effect of 4 different target positions on the accuracy of ARPA information. The results are as follows. 1. The radar echo signal data of T. S. FUKAE MARU were collected in 36 aspect angles from 0°through 350°at 10°interval. 2. For four target positions assumed to the radar echo signal data, the statistics of each positions were obtained at 36 aspect angles using 63 scan data. 3. Monte-Carlo simulation was carried out and the results for different ARPA positions were compared with the accuracy requirement stipulated by IMO. 4. It is recommened that the nearest point to own ship in the center line bisecting the echo signal is to be chosen as an APRA position.
