ACCURACY LIMITATIONS OF RADAR WITH RESPECT TO SHIP COLLISION AVOIDANCE SYSTEMS

Collision avoidance systems (CAS) which use range and angle information derived from normal ship radar echoes are limited in their effectiveness. The CAS output is only as good as the radar input. This paper examines the radar dependent factors of a collision avoidance system, i.e., the radar parameters, environmental effects and ship target characteristics which determine the quality of information furnished to the CAS. The factors include range and angle accuracy; sea, land and rain clutter, attenuation and backscatter; and also ship roll, pitch, yaw, amplitude variations and scintillation or glint. Root sum squared (RSS) standard deviation errors are summarized and radar performance is determined for normal ship return echoes and for transponder enhanced ships. The closest point of approach is calculated by considering ship length, ship position uncertainty due to radar errors and the virtual miss distance which results after a particular time to go with no further effective steering. The results indicate that for C.P.A.'s less than 2 NM a high accuracy digital radar with a ship enhanced transponder is required for effective ship collision avoidance systems in rivers and harbors. Radar, environment and ship related errors make any CAS that derives its input from the normal ship radar returns of present day radars ineffective at close ranges.

  • Supplemental Notes:
    • Presented at the April 24-26th 1972 New Orleans RTCM Assembly Meeting. Volume 1-Papers AA and A thru F-Marine Traffic Systems, Volume 2-Papers G thru L-Safe Ship Operations, Volume 3-Papers M thru Q-Maritime Satellite Systems, Volume 4-Papers R thru Z-Trends in Maritime Communications. SOLD ONLY AS A COMPLETE FOUR VOLUME SET $10.00 PER SET.
  • Corporate Authors:

    Radio Technical Commission for Marine Services

    P.O. Box 19087
    Washington, DC  USA  20036
  • Authors:
    • Moore, T A
  • Publication Date: 1972-4-24

Subject/Index Terms

Filing Info

  • Accession Number: 00033713
  • Record Type: Publication
  • Source Agency: Radio Technical Commission for Marine Services
  • Files: TRIS
  • Created Date: Sep 15 1972 12:00AM