Radar orientation

Introduction to Basic Radar- For New Lookouts & Bridge Watch keepers
1. What Radar Is (and What It Is Not)
RADAR = Radio Detection And Ranging- This means we using radio waves transmitted in a specific direction(bearing) and the time it takes for the wave to travel out and come back is converted into a measurement of range and bearing
Radar works by:
Transmitting a short pulse of radio energy
The pulse travels at the speed of light
It strikes an object (ship, land, buoy, squall)
Part of the energy reflects back to the antenna
The radar calculates:
Time delay → Distance (range)
Antenna direction → Bearing
Key Understanding for Lookouts
Radar does not “see” objects — it displays reflected energy.
This means:
A large steel vessel produces a strong, clear echo
A small wooden or fiberglass boat, kayak, or RHIB may:
Appear weak
Appear intermittently
Not appear at all
Rain, squalls, sea clutter, and swell can:
Create false echoes
Mask real targets
Change rapidly with conditions
⚠️ Radar can lie — confidently.
Critical Watchkeeping Rule
Radar supports the lookout — it never replaces eyes, ears, AIS awareness, or judgement.

2. Radar Orientation Modes
(How the Picture Is Presented)
Understanding orientation is essential before trusting bearings and movement.
North Up (N-Up)
North is always fixed at the top of the screen
The radar picture does not rotate
Own ship moves within the picture
✅ Best for:
Overall situational awareness
Chart comparison
Training and teaching radar interpretation
Understanding relative geography
🧠 Think of it as a moving chart with radar echoes
⚠️ Slightly slower for immediate collision decisions unless the user is experienced.
Head Up (HU)
Ship’s heading is always at the top
The radar picture rotates as the vessel turns
Targets move relative to the ship’s bow
✅ Best for:
Immediate collision avoidance
“What is directly ahead of me right now?”
⚠️ Caution for new lookouts
Bearings are relative, not true
A course change rotates the entire picture — this can be disorientating
Course Up (CU)
Top of screen aligns with vessel’s Course Over Ground
Picture remains stable unless course changes significantly
Resets when course change exceeds a preset value
✅ Best for:
Planned track monitoring
Long steady legs
Pilotage support when course is stable
⚠️ Less intuitive during frequent manoeuvring.
3. Initial Radar Setup
The First 60 Seconds
Before interpreting targets, the radar must be properly set.
Poor setup = false confidence.
a) Range Scale
Short ranges (0.75–3 NM):
Collision avoidance
Close-quarters monitoring
Medium to long ranges (6–12 NM+):
Traffic awareness
Weather and land detection
🔑 Best Practice
Always scan at least two ranges
If close range is clear:
Increase range to detect developing situations early
b) Gain
(Receiver sensitivity — critical for small or weak targets)
Controls how much reflected energy is displayed
Too low:
Small targets disappear
False sense of safety
Too high:
Screen fills with speckle and noise
Real targets become harder to distinguish
Correct setting looks like:
Light background speckle
Solid targets clearly defined
Small echoes visible but not drowned
c) Tuning (Manual or Auto)
Aligns transmitter and receiver for maximum performance
Manual tuning:
Adjust until targets are strongest and clearest
Auto tuning:
Modern systems do this very well
Still worth knowing manual tuning in case of:
Sensor degradation
Heavy rain
System faults
d) Sea Clutter (STC)
Reduces echoes from waves close to the vessel
Too little:
Near field cluttered
Small close targets masked
Too much:
Small vessels near the bow disappear
🔑 Set sea clutter gradually
Clear the sea return
Preserve small, hard echoes
e) Rain Clutter (FTC)
Reduces returns from rain and squalls
⚠️ High risk setting
Overuse can hide:
Small vessels
Buoys
Fishing gear
Best practice:
Use only when needed
Reduce as conditions improve

5. Target Detection & Acquisition

2. Radar Orientation Modes
(How the Picture Is Presented)
Understanding orientation is essential before trusting bearings and movement.
North Up (N-Up)
North is always fixed at the top of the screen
The radar picture does not rotate
Own ship moves within the picture
✅ Best for:
Overall situational awareness
Chart comparison
Training and teaching radar interpretation
Understanding relative geography
🧠 Think of it as a moving chart with radar echoes
⚠️ Slightly slower for immediate collision decisions unless the user is experienced.
Head Up (HU)
Ship’s heading is always at the top
The radar picture rotates as the vessel turns
Targets move relative to the ship’s bow
✅ Best for:
Immediate collision avoidance
“What is directly ahead of me right now?”
⚠️ Caution for new lookouts
Bearings are relative, not true
A course change rotates the entire picture — this can be disorientating
Course Up (CU)
Top of screen aligns with vessel’s Course Over Ground
Picture remains stable unless course changes significantly
Resets when course change exceeds a preset value
✅ Best for:
Planned track monitoring
Long steady legs
Pilotage support when course is stable
⚠️ Less intuitive during frequent manoeuvring.
3. Initial Radar Setup
The First 60 Seconds
Before interpreting targets, the radar must be properly set.
Poor setup = false confidence.
a) Range Scale
Short ranges (0.75–3 NM):
Collision avoidance
Close-quarters monitoring
Medium to long ranges (6–12 NM+):
Traffic awareness
Weather and land detection
🔑 Best Practice
Always scan at least two ranges
If close range is clear:
Increase range to detect developing situations early
b) Gain
(Receiver sensitivity — critical for small or weak targets)
Controls how much reflected energy is displayed
Too low:
Small targets disappear
False sense of safety
Too high:
Screen fills with speckle and noise
Real targets become harder to distinguish
Correct setting looks like:
Light background speckle
Solid targets clearly defined
Small echoes visible but not drowned
c) Tuning (Manual or Auto)
Aligns transmitter and receiver for maximum performance
Manual tuning:
Adjust until targets are strongest and clearest
Auto tuning:
Modern systems do this very well
Still worth knowing manual tuning in case of:
Sensor degradation
Heavy rain
System faults
d) Sea Clutter (STC)
Reduces echoes from waves close to the vessel
Too little:
Near field cluttered
Small close targets masked
Too much:
Small vessels near the bow disappear
🔑 Set sea clutter gradually
Clear the sea return
Preserve small, hard echoes
e) Rain Clutter (FTC)
Reduces returns from rain and squalls
⚠️ High risk setting
Overuse can hide:
Small vessels
Buoys
Fishing gear
Best practice:
Use only when needed
Reduce as conditions improve

7. VRM & EBL – Measuring Tools

7. VRM & EBL
Simple, Powerful Collision Tools
VRM (Variable Range Marker)
Measures distance to a target
EBL (Electronic Bearing Line)
Measures bearing to a target
Uses
Confirm collision risk
Monitor bearing stability
Check passing distances
🔑 Simple Drill
Place EBL through the centre of a contact
Observe over time:
Bearing steady
Range reducing
Collision risk exists
This works even without ARPA.
8. Parallel Indexing (PI)
A powerful but often underused safety tool.
What It Is
A fixed radar line offset from a known feature (coast, channel edge, track limit).
Why It Matters
Immediate visual warning if the vessel is:
Closing the coast
Drifting off track
Requires no calculation
Works in:
Darkness
Rain
Poor visibility
Typical Uses
Coastal passages
Night navigation
Pilotage support
Backup to ECDIS
🧠 If the PI line moves — something is wrong.
9. Radar Watchkeeping Discipline
Radar watchkeeping is active, not passive.
Good lookout habits:
Regular range changes
Continuous mental plotting
Compare radar with:
Visual sightings
AIS
Chart / ECDIS
Maintain a broad traffic picture
⚠️ Common Errors
Over-gaining the display
Ignoring weak or intermittent echoes
Assuming AIS shows everything
Trusting ARPA without understanding
10. Final Training Message for Lookouts
Radar does not prevent collisions.
People using radar correctly do.
The objective is always:
Early detection
Early understanding
Early action
A good lookout uses radar to:
See sooner
Think clearer
Act with confidence