REQUIREMENTS OF A
RADAR FOR THE MARITIME
ENVIRONMENT
By Captain (SA Navy ) Nick Snyman
Senior Staff Officer Maritime Technology
Directorate Technology Development
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AIM
To provide an operational view of radar
operating conditions in the maritime
environment
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SCOPE
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Mission of the SA Navy
Maritime environmental conditions
Uses of radar in maritime environment
Operational implications
Conclusion
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MARITIME ENVIRONMENTAL
CONDITIONS
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Life at sea is good
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Pretty sights
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Beautiful views for a
submariner
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Lovely day in the sun
and calm seas
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Start dreaming that
life could not be
better
….. And you are expect
to see these sights
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AND THEN THE REALITY OF SEA LIFE STRIKES!!!!!!!!
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MARITIME ENVIRONMENTAL
CONDITIONS (The other side of
life at sea)
RomanRock.wmv
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MARITIME ENVIRONMENTAL
CONDITIONS
• Clutter (Rain and Sea)
– Obscures small contacts
– No clear close range picture
– Danger to vessels in confined space
• Ducting
– Ducting increases clutter and increased
anomalous propagation
– Increased radar range
• Multi-pathing
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Factors in Radar Equation
Multipath
Sea & Rain Clutter
Clutter
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Sea Clutter Illumination AREA
θVertical
Area = k(Range)(θH)(τ)(secγ)
θHorizontal
Τ = Pulse Length
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Sea Clutter (SS=3)
Clutter = 0 > Radar Horizon
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Rain Clutter Illumination VOLUME
θVertical
Volume = k(Range)2(θH)(θH)(τ)
θHorizontal
Τ = Pulse Length
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Rain Clutter (1mm/hour)
Clutter = 0 > Radar Horizon
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Sea & Rain Clutter
Influence on Detectability in Naval Environment
Pd = 32km
FSG
FSG
Pd = 11km
Sea
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Rain Clutter
Contacts
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MAGNETRON X-BAND
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SOLID STATE X-BAND PULSE COMPRESSION
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X-BAND MAGNETRON
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SOLID STATE X-BAND PULSE COMPRESSION
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MARITIME ENVIRONMENTAL
CONDITIONS (1)
• Clutter (Rain and Sea)
– Obscures small contacts
– No clear close range picture
– Danger to vessels in confined space
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MARITIME ENVIRONMENTAL
CONDITIONS (2)
• Ducting
– Ducting increases clutter and increased
anomalous propagation
– Increased radar range
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Radar Ducting
Ducted beam
Normal radar beam
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MARITIME ENVIRONMENTAL
CONDITIONS (3)
• Multi-pathing
– Cannot detect and track low flying targets
– Ineffective radar against fast low flying
incoming missiles
• Effect of side lobe interference in littoral
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Multipath: Principle of Null & Sum Values
RDirect
RMultipath
θ
θ
Path Difference = λ/2
Path Difference = λ
Direct
Direct
Multipath
Multipath
4x Amplitude
Sum
ZERO
Sum
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Multipath: Range Holes
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MARITIME ENVIRONMENTAL
CONDITIONS (4)
• Effect of side lobe interference in littoral
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SIDE LOBES
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USES OF MARITIME RADAR
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USES OF MARITIME RADAR
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Collision avoidance
Navigation and Blind pilotage
– Good range discrimination
– Close range clear picture
– High definition
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USES OF MARITIME RADAR
• Surveillance
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Long range, early warning
Close-in surveillance
Range discrimination
3D picture
Track while scan
Track multiple contacts
• Small contacts
• Low flying contacts
• Tracking radar
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OPERATIONAL IMPLICATIONS
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OPERATIONAL IMPLICATIONS
• Range discrimination to discriminate
between contacts in close proximity
• Lack of detection ability in clutter
– Missing the target
– Own ship detected first
• Require recognition and identification
ability
• Interference from other radars
• Antenna height restrictions
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Cannot see the spur
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Interference caused by radar, clutter and
radar shadow
Clutter
Shadow caused by mast
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Radar Picture of land-based radar
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CONCLUSION
• Surveillance, detection and identification is
important to the Navy
• Unique maritime environmental conditions
affects radar performance
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Sea conditions - stability
Sea and rain clutter
Ducting
Muti-pathing
Effect of the littoral on the side lobe contacts
• Different types of radar
– Navigation
– Long range surveillance
– Tracking
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THANK YOU!!
QUESTIONS??
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Multipath (“Two-way only!”)
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Sea Surface Reflection: (1) Amplitude ~ 100% (2) Phase = 180%
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Sea Surface Reflection: Frequency
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MRR vs SSM: RCS = 0.1m2 @ 15m
SSM
Pd (80%) = 25km
Sea
Sub Clutter Visibility = 48dB
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Radar Data Reduction
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SEA TRAFFIC DENSITY AROUND THE WORLD
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Sea Clutter (AREA Illumination)
m2/m2
m2
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