Chapter 2

RADAR OBSERVATION

2.1Radar Picture, Target Properties and Radar Pulse

Strength of reflection

The strength of the reflected echo depends not only on the height and size of the target but also its shape, material and the angle at which the radio pulse strikes it.

Actual topography and radar picture

The radar cannot display topography in its actual shape.

Black areas are strong reflection targets.

Coastline difficult to display.

Figure 2-1 Radar picture and actual topography

Target size and strength of reflected echo

The size of a target has little to do with the strength of the reflected echo. If the radio pulse strikes the target at a right angle, even a small target will re- turn a strong echo, provided its material is a good radar target.

Radar picture and how the pulse strikes a target

2.2 Range Resolution

Range resolution is a measure of the capability of a radar to display as separate pips the echoes re- ceived from two targets which are on the same bearing and are close together.

The main factor which affects range resolution is pulselength. Two targets on the same bearing, close together, cannot be seen as two distinct ech- oes on the display unless they are separated by a distance greater than one-half the pulselength.

A return echo will be weak if the angle at which a radio pulse strikes a target is small. For example, flat surfaces, such as sandy beaches, sandbars and mudbanks have almost no area that can reflect en- ergy back to the radar. Conical surfaces, such as a lighthouse, generate a weak return echo because their shape diffuses most of the radiated energy.

Transmitted radar pulse

Transmitted radar pulse

Radar is able to display two distinct target echoes.

Target

Target

Radar sees only the near side of targets. For ex- ample, it cannot show you what is behind a sea wall or an island. The echo of a mountain peak may appear on the radar as a peninsula or small island.

Target material and reflected echo

Generally, steel objects return a very strong echo, and reefs and water return a weak echo. The weak- est echoes come from wood and fiberglass ob- jects. In summary, non-metallic objects and flat or conical objects are not good radar targets.

Radar cannot display targets as separate echoes because they are within the pulselength.

Figure 2-2 Range resolution

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Furuno FR-8111, FR-8251 manual Radar Observation, Radar Picture, Target Properties and Radar Pulse, Range Resolution

FR-8251, FR-8111 specifications

Furuno has long been a leader in marine electronics, and its FR-8251 and FR-8111 radar systems continue that tradition. Both are advanced systems designed specifically for professional mariners who demand high performance, reliability, and technological sophistication in their navigational tools.

The Furuno FR-8251 is a powerful radar system that boasts a range of features tailored for commercial vessels. With a 25 kW transmitter, the FR-8251 delivers exceptional performance, providing a clearer and more detailed image of the maritime environment. It is equipped with advanced signal processing technology, including the Doppler processing feature, which allows for the detection of moving targets. This is highly beneficial for collision avoidance, as it provides accurate information regarding the speed and direction of other vessels.

Another noteworthy feature of the FR-8251 is its large, high-resolution display that enhances visibility and ease of use, even in challenging weather conditions. The user interface is straightforward, allowing for quick adjustments and easy navigation through the various settings. It supports a variety of display formats and allows for customization, enabling operators to tailor the information presented according to their specific needs.

On the other hand, the Furuno FR-8111 is equally impressive and designed as a more compact solution without sacrificing performance. This model comes with a 12 kW output and is specifically crafted for smaller vessels, yet it still delivers high-quality radar coverage. Utilizing Furuno’s renowned Automatic Target Tracker (ATT) technology, the FR-8111 enables mariners to efficiently track multiple targets, significantly enhancing situational awareness.

Additionally, both the FR-8251 and FR-8111 come with integrated ARPA (Automatic Radar Plotting Aid), providing users with sophisticated tools for navigation and collision avoidance. The presence of multiple target tracking empowers operators to make informed decisions, optimizing safety at sea.

Furuno’s commitment to reliability and durability is evident in both models, which are designed to withstand the harsh marine environment. Their robust build quality ensures longevity, while their advanced technologies offer peace of mind.

Both the Furuno FR-8251 and FR-8111 are excellent choices for professional mariners seeking cutting-edge radar systems. With their impressive performance, user-friendly interfaces, and advanced technologies, these radar systems set the standard in marine navigation, providing essential support for safe and efficient voyages.