Marine radar
Encyclopedia
Marine radars are x-band or s-band radar
to provide bearing and distance of ships and land targets in vicinity from own ship (radar scanner) for collision avoidance and navigation at sea.
In port or in harbour, vessel traffic service
radar systems are used to monitor and regulate ship movements in busy waters.
should be used to get the information of movement and the risk of collision (bearing, distance, CPA, TCPA) of other ships in vicinity.
information for navigators onboard ships. Ship position could be fixed by the bearing and distance information of land target on radar screen.
is a conjecture about the range of a maritime radar is affected by pulse length as opposed to its amplitude.
The radar range equation states the maximum theoretical range of a radar system based on the output power and sensitivity of the receiver. It may be modified by taking into account the curvature of the earth. This drastically reduces the range for maritime radars.
In order to increase range maritime radars increase the Pulse Repetition Rate (PRF). PRF is in essence how often the magnetron is fired per second. In essence this means that the actual range is affected by the number of pulses that are fired and NOT the amplitude. Convention would have us believe that the amplitude of the pulse should affect the range.
Consider a light in a window, we are sitting 1 mile away, the light is switched on for a minute, we are looking at the window and don't see it. If the light is on for two minutes would we see it? No. In order to make if visible at 1 mile we would increase the brightness (or it's amplitude)!
In the world of RADAR to increase the range one can lengthen the pulse length. Whilst the total amount of energy has increased the amplitude has not. Watson postulated that the reason range increased as pulse length increased was due to probability, If the pulse length is longer then the probability that an echo will return is increased thus increasing the effective range of the system.
Phil Watson BEng, CEng, MIEI is a Radar Consultant in Naval Radar. His full paper 'Statistical Anomalies in Radar Radiation' is classified however an excerpt on Radar Power conjecture was released in print format in 1990, it is also briefly mentioned on the authors website, link below.
Radar
Radar is an object-detection system which uses radio waves to determine the range, altitude, direction, or speed of objects. It can be used to detect aircraft, ships, spacecraft, guided missiles, motor vehicles, weather formations, and terrain. The radar dish or antenna transmits pulses of radio...
to provide bearing and distance of ships and land targets in vicinity from own ship (radar scanner) for collision avoidance and navigation at sea.
In port or in harbour, vessel traffic service
Vessel Traffic Service
A vessel traffic service is a marine traffic monitoring system established by harbour or port authorities, similar to air traffic control for aircraft...
radar systems are used to monitor and regulate ship movements in busy waters.
Collision avoidance
As required by COLREGS, all ships shall maintained a proper radar lookout if it is available onboard to obtain early warning of risk of collision. Radar plotting or ARPAAutomatic Radar Plotting Aid
A marine radar with automatic radar plotting aid capability can create tracks using radar contacts. The system can calculate the tracked object's course, speed and closest point of approach , thereby knowing if there is a danger of collision with the other ship or landmass.Development of ARPA...
should be used to get the information of movement and the risk of collision (bearing, distance, CPA, TCPA) of other ships in vicinity.
Navigation
Marine radar systems can provide very useful radar navigationRadar navigation
Marine and aviation radar systems can provide very useful navigation information in a variety of situations. When a vessel is within radar range of land or special radar aids to navigation, the navigator can take distances and angular bearings to charted objects and use these to establish arcs of...
information for navigators onboard ships. Ship position could be fixed by the bearing and distance information of land target on radar screen.
Radar Controls
Marine radar has performance adjustment controls for brightness and contrast, gain, tuning, sea clutter and rain clutter suppression, and other interference reduction. Other common controls consist of range scale, bearing cursor, fix/variable range marker or bearing/distance cursor.Watson Radar Power Conjecture
The Watson Conjectureis a conjecture about the range of a maritime radar is affected by pulse length as opposed to its amplitude.
The radar range equation states the maximum theoretical range of a radar system based on the output power and sensitivity of the receiver. It may be modified by taking into account the curvature of the earth. This drastically reduces the range for maritime radars.
In order to increase range maritime radars increase the Pulse Repetition Rate (PRF). PRF is in essence how often the magnetron is fired per second. In essence this means that the actual range is affected by the number of pulses that are fired and NOT the amplitude. Convention would have us believe that the amplitude of the pulse should affect the range.
Consider a light in a window, we are sitting 1 mile away, the light is switched on for a minute, we are looking at the window and don't see it. If the light is on for two minutes would we see it? No. In order to make if visible at 1 mile we would increase the brightness (or it's amplitude)!
In the world of RADAR to increase the range one can lengthen the pulse length. Whilst the total amount of energy has increased the amplitude has not. Watson postulated that the reason range increased as pulse length increased was due to probability, If the pulse length is longer then the probability that an echo will return is increased thus increasing the effective range of the system.
Phil Watson BEng, CEng, MIEI is a Radar Consultant in Naval Radar. His full paper 'Statistical Anomalies in Radar Radiation' is classified however an excerpt on Radar Power conjecture was released in print format in 1990, it is also briefly mentioned on the authors website, link below.
External links
- http://www.radartutorial.eu/01.basics/rb13.en.html
- http://earth.esa.int/applications/data_util/SARDOCS/spaceborne/Radar_Courses/Radar_Course_III/radar_equation.htm
- http://www.alphalpha.org/radar/intro_e.html#Portata%20non%20ambigua
- http://www.macuait.com/index.php/research/14-watson-radar-conjecture