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IEC 62388 — Maritime Navigation: Radar Systems for Shipborne Use
The definitive performance standard for shipborne radar equipment meeting IMO SOLAS requirements
IEC 62388 is the core international standard governing shipborne radar systems used for maritime navigation. It defines the minimum operational and performance requirements for radar equipment installed on vessels regulated by the International Maritime Organization (IMO) under the SOLAS convention. The standard covers both X-band (9 GHz / 3 cm) and S-band (3 GHz / 10 cm) radar systems, including their associated target-tracking functions (ARPA/MARPA), transponder (SART) detection, and display performance. Compliance with IEC 62388 is mandatory for type-approval of maritime radar equipment under IMO Resolution MSC.192(79).
IEC 62388 was developed to replace and consolidate the earlier IEC 60936 series, IEC 60872 series (ARPA), and IEC 61023 (MARPA) into a single comprehensive standard that reflects modern solid-state radar technology and digital display requirements.
1. Radar Performance Requirements
The standard defines separate performance tiers for different radar classes and specifies minimum detection ranges for standard targets under defined environmental conditions:
| Target Type | X-band (9 GHz) Detection Range | S-band (3 GHz) Detection Range | Detection Probability |
|---|---|---|---|
| Large vessel (>10,000 GT) | ≥ 37 km (20 NM) | ≥ 37 km (20 NM) | ≥ 80% |
| Small vessel (10 m length) | ≥ 9.3 km (5 NM) | ≥ 9.3 km (5 NM) | ≥ 80% |
| Navigation buoy (with radar reflector) | ≥ 7.4 km (4 NM) | ≥ 5.6 km (3 NM) | ≥ 70% |
| Radar transponder (SART) | ≥ 9.3 km (5 NM) | ≥ 9.3 km (5 NM) | ≥ 95% |
| Shoreline (cliff 60 m high) | ≥ 37 km (20 NM) | ≥ 37 km (20 NM) | ≥ 90% |
The minimum antenna rotation rate is 24 r/min for X-band and 18 r/min for S-band. The horizontal beamwidth must not exceed 2° for X-band and 5° for S-band, while vertical beamwidth must be between 15° and 30° to maintain target visibility during vessel pitch and roll of up to ±10°.
A critical operational requirement is the «sea clutter» performance specification. The radar must provide automatic and manual sea-clutter control that ensures detection of a 10 m² target at 5 NM range in sea state 4 (significant wave height 1.25–2.5 m) with no more than 6 dB degradation relative to calm-sea performance. This demands sophisticated logarithmic amplifier chains or digital IF processing with adaptive gain control.
2. Target Tracking: ARPA and MARPA
IEC 62388 mandates automatic radar plotting aid (ARPA) for ships of 10,000 GT and above, and minimum-requirement ARPA (MARPA) for smaller vessels. The tracking performance requirements are among the most demanding aspects of the standard:
| Tracking Parameter | ARPA Requirement | MARPA Requirement |
|---|---|---|
| Tracking capacity | ≥ 200 targets simultaneously | ≥ 50 targets simultaneously |
| Acquisition range | Auto: 24 NM; Manual: 48 NM | Manual: 24 NM |
| Relative course accuracy (steady track) | ≤ 5° after 60 s | ≤ 7° after 60 s |
| Relative speed accuracy (steady track) | ≤ 1.0 kn after 60 s | ≤ 1.5 kn after 60 s |
| CPA accuracy | ≤ 0.1 NM after 60 s | ≤ 0.3 NM after 60 s |
| TCPA accuracy | ≤ 0.3 min after 60 s | ≤ 1.0 min after 60 s |
| Track swap/target swap ratio | ≤ 1% per scan | ≤ 2% per scan |
The tracking algorithm must employ a combination of α-β or Kalman filtering with gating and data association logic to handle manoeuvring targets, multiple target crossings, and temporary target fade due to sea-state or interference. The standard specifically requires that the tracker be capable of maintaining lock on a target executing a 30° turn at 3°/s without track loss.
3. Display Performance and Human-Machine Interface
The radar display must provide a minimum resolution of 1280 x 1024 pixels with a daylight-viewable luminance of at least 100 cd/m² and a contrast ratio better than 100:1 in ambient illumination up to 75,000 lux (direct sunlight on the bridge). The standard explicitly prohibits display refresh rates below 20 Hz and insists on anti-aliased graphics for all vector-based symbology.
A major engineering improvement in the 2013 edition (currently the latest) is the mandatory integration of electronic chart (ECDIS) overlay capability. The radar image must be geo-referenced to the WGS-84 datum and overlayable on an ENC chart display with a registration accuracy better than one pixel at the selected range scale. This requires real-time chain of transformations from radar polar coordinates through vessel reference frame to geodetic coordinates.
Key user interface requirements include:
- North-up, course-up, and head-up orientation modes — all three must be supported with instant switching.
- True motion and relative motion display modes — with seamless transition.
- Trail echoes (echo stretch) — minimum 3 selectable persistence levels.
- EBL (electronic bearing line) and VRM (variable range marker) — two independent EBL/VRM pairs minimum.
- Guard zone — at least two independent guard zones with sector and circular shapes, with audible and visual alarm outputs.
- Alarm management — prioritised alarm queue conforming to IMO MSC.302(87) for bridge navigational watch alarm system (BNWAS) integration.
4. Engineering Design Insights for Solid-State Radar Transceivers
The transition from magnetron-based transmitters to solid-state technology has been one of the most significant developments in maritime radar engineering. IEC 62388 accommodates both technologies but implicitly raises the bar for solid-state designs through its demanding clutter and detection requirements:
Solid-state radar transceivers typically use pulse compression techniques (e.g., linear frequency modulation or Barker coding) to achieve the required range resolution with lower peak power (typically 100–300 W peak vs 10–25 kW for magnetron). However, the pulse compression sidelobe ratio must be better than −30 dB to prevent strong-target sidelobes from masking weak targets. Achieving this demands sophisticated mismatch filter design in the digital receiver, often using least-squares or windowed compression kernels.
Receiver dynamic range: The maritime radar environment presents an extreme dynamic range challenge — from sea clutter returns within 100 m to a distant target at 48 NM, the signal power variation can exceed 100 dB. The standard requires a minimum instantaneous dynamic range of 70 dB at IF, which practically dictates the use of logarithmic amplifiers or high-dynamic-range digital receivers with 16-bit or higher ADCs at intermediate frequencies.
Doppler processing for target enhancement: While IEC 62388 does not mandate Doppler capability (unlike aviation weather radar), many modern solid-state designs implement moving target indication (MTI) to suppress sea and rain clutter. The notch filter bandwidth must be carefully tuned — too narrow fails to reject enough clutter, too wide cancels slow-moving targets. A Doppler notch of 30–100 Hz (corresponding to 0.5–1.6 kn radial velocity at X-band) represents a typical engineering compromise.
5. Conclusion
IEC 62388 is a comprehensive, technically demanding standard that ensures shipborne radar systems meet the safety-critical requirements of modern maritime navigation. From minimum detection ranges and tracking accuracy to display ergonomics and solid-state transceiver design, the standard covers every aspect of radar performance. For radar engineers and system integrators, understanding the interplay between antenna pattern design, receiver dynamic range, clutter processing algorithms, and display rendering is essential for developing equipment that will pass the rigorous type-approval process and operate reliably in the world’s most demanding maritime environments.
Q1: What is the difference between IEC 62388 and the older IEC 60936?
IEC 62388 consolidates and supersedes IEC 60936 (radar performance) and IEC 60872 (ARPA) into one standard. It adds modern requirements for solid-state transmitters, electronic chart overlay, digital interfaces (IEC 61162/NMEA 2000), and enhanced clutter performance.
IEC 62388 consolidates and supersedes IEC 60936 (radar performance) and IEC 60872 (ARPA) into one standard. It adds modern requirements for solid-state transmitters, electronic chart overlay, digital interfaces (IEC 61162/NMEA 2000), and enhanced clutter performance.
Q2: Is S-band radar mandatory on all ships?
No. SOLAS Chapter V Regulation 19 requires all ships of 3,000 GT and above to carry two radar systems, one of which must be S-band (10 cm). Ships below 3,000 GT may carry only X-band. S-band is preferred in heavy rain or sea clutter because of its lower attenuation and longer wavelength.
No. SOLAS Chapter V Regulation 19 requires all ships of 3,000 GT and above to carry two radar systems, one of which must be S-band (10 cm). Ships below 3,000 GT may carry only X-band. S-band is preferred in heavy rain or sea clutter because of its lower attenuation and longer wavelength.
Q3: What is the significance of the 2013 Edition with Corrigendum 1 (2014)?
The 2013 edition introduced major updates including mandatory ECDIS overlay, enhanced ARPA tracking capacity (increased from 100 to 200 targets), and updated display luminance requirements. The 2014 corrigendum clarified antenna side-lobe and receiver recovery time specifications.
The 2013 edition introduced major updates including mandatory ECDIS overlay, enhanced ARPA tracking capacity (increased from 100 to 200 targets), and updated display luminance requirements. The 2014 corrigendum clarified antenna side-lobe and receiver recovery time specifications.
Q4: Can a radar meet Type Approval if it uses a magnetron transmitter?
Yes. The standard is technology-neutral. However, magnetron-based radars must still meet the same detection, clutter-rejection, and reliability requirements as solid-state designs. In practice, many manufacturers are transitioning to solid-state for lower life-cycle cost and improved MTBF.
Yes. The standard is technology-neutral. However, magnetron-based radars must still meet the same detection, clutter-rejection, and reliability requirements as solid-state designs. In practice, many manufacturers are transitioning to solid-state for lower life-cycle cost and improved MTBF.
