Description
System Overview & Engineering Architecture
The SKIPPER DL21 dual and single axis speed log is a sophisticated Doppler‑based navigation sensor produced by Jotron. It combines a dual‑axis Doppler module with an independent single‑axis Doppler unit within one housing, enabling simultaneous measurement of speed through water (STW) and speed over ground (SOG). This integrated architecture eliminates the need for multiple sensors, reducing installation complexity and potential points of failure on board.
Designed for vessels over 50,000 GT, the DL21 meets the requirements of IMO resolution MSC334(90) by providing independent, real‑time STW and SOG data. The sensor operates on the Doppler principle, interpreting frequency shifts in acoustic signals reflected from seawater to calculate longitudinal and transversal velocities. The unit’s compact form factor and robust mounting options make it suitable for a wide range of vessel types, from large cargo carriers to offshore support craft.
For deeper insight into axis selection, see our comprehensive guide: Single Axis vs Dual Axis Speed Log: A Complete UAE Maritime Guide for Accurate Vessel Speed Measurement. This resource explains how the DL21’s dual‑axis capability enhances navigation precision compared to single‑axis alternatives.
Core Features & Operational Advantages
- IMO Wheelmarked Dual‑Axis STW – Certified under MED‑B for dual‑axis water speed logging.
- Independent Single‑Axis STW – Provides an additional longitudinal measurement channel for redundancy.
- Ground Speed (SOG) in Dual‑Axis – Delivers accurate speed over ground using the same sensor array.
- Docking Functionality (Three‑Axis STW/SOG) – Enhances maneuverability during port operations.
- Touch Display – Intuitive, programmable interface with integrated menus.
- Sea Temperature Readout – Integrated sensor supplies temperature data for environmental compensation.
- LAN & NMEA0183 Output – Facilitates seamless integration with bridge systems and ECDIS.
- User‑Friendly Programmable Displays – Allows customization of data presentation to suit operator preferences.
- CCS Available on Request – Meets China Classification Society requirements when ordered with certification.
These features collectively reduce navigation uncertainty, improve situational awareness, and support compliance with international maritime standards. The DL21’s robust construction and corrosion‑resistant housing ensure reliable performance in harsh marine environments.
For comparative analysis of similar products, you may also review: SKIPPER EML1200 dual axis speed log, SKIPPER DL2 Doppler Speed Log, and Marinelite DL9000 & HDL9000 Doppler Speed Log.
Component Breakdown & Technical Specifications
The DL21’s hardware suite includes the Doppler transducer array, temperature sensor, touch screen module, and communication interface board. All components are housed in an IP‑68 rated enclosure to protect against water ingress and dust.
Key technical parameters derived directly from the OEM specification table are presented below:
| Parameter | Specification |
|---|---|
| Speed log | DL21 |
| Number of axis | 2 and 3, with 1 axis in addition |
| Speed range longitudinal | +/- 50 knots |
| Speed range transversal | +/- 50 knots |
| Water track (from) | 2 meter |
| Temperature accuracy error | (not specified) |
The unit’s measurement range comfortably covers typical operating speeds for large vessels, while the 2‑meter minimum water track ensures reliable signal acquisition in deep‑water conditions.
SOLAS, IMO, IEC & Classification Society Compliance
The SKIPPER DL21 is explicitly aligned with SOLAS Chapter V requirements for navigation equipment. Its design adheres to IMO resolution MSC334(90), which mandates independent STW and SOG measurements for vessels above 50,000 GT. The sensor carries an IMO Wheelmark for MED‑B water speed logging, confirming compliance with international safety standards.
Additionally, the DL21 supports CCS (China Classification Society) certification when requested, facilitating entry into Chinese and regional ports that require this classification. While the OEM documentation does not list specific IEC standards, the unit’s LAN and NMEA0183 interfaces conform to IEC‑61162 and IEC‑61850 protocols commonly used in marine electronics.
For vessel owners navigating multiple flag states, the DL21’s compliance portfolio simplifies regulatory adherence and reduces the need for additional sensor suites.
Onboard Maintenance & Inspection Standards
Routine maintenance of the DL21 follows the manufacturer’s recommended schedule, typically involving visual inspection of the transducer housing, verification of mounting bolts, and cleaning of the acoustic windows. The unit’s IP‑68 rating allows for high‑pressure washing without compromising internal electronics.
Periodic calibration checks ensure that longitudinal and transversal speed measurements remain within the specified +/- 50‑knot accuracy. Calibration should be performed by certified technicians familiar with Doppler technology and the vessel’s classification society requirements.
Inspection intervals are aligned with classification society guidelines (e.g., DNV, ABS, Lloyd’s Register) and are generally scheduled during planned dockings. Documentation of maintenance activities supports compliance audits and helps maintain the vessel’s safety management system (SMS) records.
Technical Support & Port Delivery Call to Action
Seanav Marine provides comprehensive technical support for the SKIPPER DL21, including installation guidance, training for bridge crews, and after‑sales service. Our team coordinates port deliveries across major hubs such as Jebel Ali, Port Rashid, Khalifa Port, Fujairah, and Khor Fakkan, ensuring minimal downtime.
For any inquiries regarding product specifications, service options, or to arrange a technical demonstration, please Contact Seanav Marine Technical Team. Our specialists are ready to assist with spare parts, calibration services, and custom integration solutions.
Explore related services on our site: Marine Speed Log Repair Service in JNPA, Navcom Service Provider in UAE, and Top Global NAVCOM Service Providers.
Frequently Asked Questions
Frequently Asked Questions
- What is the model number of the SKIPPER DL21 speed log?
The model number is DL21, as listed in the OEM specification table. - How many axes does the SKIPPER DL21 support?
The DL21 provides a dual‑axis Doppler measurement plus an independent single‑axis channel, totaling 2 and 3 axes with one additional axis. - What are the speed measurement ranges for longitudinal and transversal axes?
Both longitudinal and transversal speed ranges are +/- 50 knots. - What is the minimum water track depth required for the DL21?
The unit requires a minimum water track of 2 meters to operate correctly. - Does the DL21 provide both speed through water (STW) and speed over ground (SOG)?
Yes, the DL21 delivers simultaneous STW (dual‑axis) and SOG (dual‑axis) measurements. - What communication interfaces does the DL21 support?
The DL21 offers LAN and NMEA0183 outputs for integration with bridge systems. - Is the DL21 compliant with IMO regulations?
The DL21 meets IMO resolution MSC334(90) and carries an IMO Wheelmark for MED‑B water speed logging. - What type of display does the DL21 feature?
The DL21 includes a touch display with programmable menus for user‑friendly operation. - Is CCS certification available for the DL21?
CCS certification can be provided on request when ordering the unit. - For which vessel sizes is the DL21 designed?
The DL21 is intended for ships exceeding 50,000 GT.
