Too Close to See Clearly? How BOTIX Is Advancing Close-Range Perception on the Water

Conventional navigational radar can detect targets over broad areas, but its performance may be limited when targets are close, slow-moving or small, such as fishing vessels, buoys and floating objects. Limited resolution and strong clutter can make these targets difficult to resolve and distinguish from environmental interference.

To address this industry challenge, BOTIX developed its 4D Imaging Small-Target Radar specifically for close-range detection. By improving resolution and resistance to interference, the radar helps detect and resolve small targets that conventional sensing equipment may struggle to distinguish, providing more precise perception support for navigational safety.

Why Can Nearby Targets Be Difficult to Detect?

In busy waters such as ports, waterways and anchorages, failure to detect nearby targets can create serious collision risks. Visual lookout and conventional navigational radar may both be challenged by small targets at close range. Even advanced X-band solid-state navigational radar may experience unstable detection or target loss under these conditions.

There are two principal reasons.

First, navigational radar has inherent minimum-range limitations. Many pulsed navigational radars use a shared antenna for transmission and reception. During pulse transmission and receiver recovery, strong leakage signals can obscure returns from nearby targets, creating a minimum detection range within which targets may be difficult to detect.

Second, navigational radar is highly susceptible to sea clutter. Reflections from the water surface become stronger at close range, rapidly reducing the signal-to-clutter ratio of small targets and making them more difficult to separate from the surrounding background.

BOTIX 4D Imaging Small-Target Radar: Enhancing Close-Range Perception

Designed and developed by BOTIX, the 4D Imaging Small-Target Radar is purpose-built for close-range small-target detection onboard vessels.

With decimeter-level range performance and high-resolution point-cloud imaging, the system provides stable close-range detection across a broad range of weather and sea conditions, complementing conventional navigational radar where more detailed perception is required.

The following test illustrates its performance under specific operating conditions.

A buoy measuring 2.4 metres in diameter and approximately 3 metres above the waterline was used as the target under Sea State 3 conditions. The image on the left shows the output from the BOTIX 4D Imaging Small-Target Radar, while the image on the right shows the output from an X-band navigational radar.

At distances beyond 500 metres, the BOTIX radar produced a clear and stable representation of the buoy. The target displayed by the X-band navigational radar was comparatively indistinct and unstable.

Within 500 metres, the target return on the X-band radar was frequently lost, while the BOTIX radar maintained stable returns throughout the tested range.

How BOTIX Detects and Resolves Small Targets at Close Range

The real challenge in close-range small-target detection is not simply receiving a return. It is reliably separating, resolving and tracking the target within a complex environment.

To address this challenge, BOTIX has introduced millimeter-wave radar technology into maritime applications and developed a series of purpose-built system and algorithm innovations.

1. System-Level Design Innovation

The BOTIX 4D Imaging Small-Target Radar was designed around the specific requirements of shipboard operation, with innovations extending from the antenna array to the processing algorithms.

The system combines high-gain narrow-beam antenna technology, a sparse two-dimensional MIMO array and a mechanically scanned multi-panel antenna architecture. It addresses technical challenges including inter-channel phase drift, synchronization between antenna panels and real-time vessel-attitude compensation, helping maintain stable and accurate angular point-cloud output with sufficient effective point density.

The system provides:

• 360° azimuth coverage

• A default scan cycle of 1 second, with configurable scan rates

• A maximum detection range of over 4 km

• Decimeter-level range accuracy

• Angular accuracy of 0.1°

• Doppler velocity resolution better than 0.1 m/s

2. Integrated Adaptive Algorithms for Stable Target Detection in Sea Clutter

Conventional detection and tracking algorithms may have limited adaptability under complex sea conditions.

BOTIX has developed an integrated, scene-adaptive processing pipeline covering point-cloud stitching, noise filtering, segmentation, clustering and automatic multi-target tracking. The system is designed not only to detect small targets but also to maintain clear and stable tracks in adverse sea conditions and complex waters.

For targets ranging from slow-moving floating objects to high-speed small craft, the system achieves an average track-initiation time of less than 10 seconds.

Technological innovation is not about accumulating specifications. Its ultimate purpose is to improve safety.

As an early innovator in maritime autonomy, BOTIX continues to invest in technologies that prevent small targets from disappearing into waves and sea clutter. By enhancing close-range detection in busy ports, narrow waterways and challenging weather, BOTIX is helping vessels understand their immediate surroundings with greater clarity and confidence.