Nautical Studies

about Marine Navigation & Technology

Is a clean radar picture a clear radar picture? (清晰的雷達)

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A harbour tug was moving through the water. A small sampan was crossing and riding on the bow wave of the tug.

It can be agreed that the height of the bow wave shown in the photo is as much as those of the sampan. The bow waves also present suitable surfaces to reflect radar pulses. As well, sea water has a high reflective rate. It is as good as steel. In contrast, the fiber-glass sampan reflects radar energy rather poorly. It could be difficult to pick up by radar.

It can be suggested that the sampan will not be visible on a radar screen if the bow wave is not visible. The signals reflected by the sampan will be suppressed if the signals reflected by the bow wave are suppressed.

Should bow waves or ship wakes be seen on a radar screen? Could radar screen a clean screen if bow waves and ship wakes of the nearby moving vessels are detected? Is a clean radar picture a better radar picture?

在照片中,一艘拖船正在水中移動,一艘小舢舨正在駛過拖船所引起的波浪。

照片中的拖船移動時所產生的海浪看來比那舢舨還要高,那些波浪亦有合適的表面以反射雷達脈衝。再者,海水具有非常高的電波反射能力,其雷達反射率可以說是僅次於鋼鐵。相比之下,玻璃纖維制造的舢舨的雷達反射率則較差,其反射的能量相當低,雷達亦可能探測不到。

如果在雷達屏幕未能探測到如照片中的海浪,那舢舨亦可能探測不到。如果將如照片中的海浪所引起的回波抑制,類似那舢板所反射信號波亦將會被抑制。

像船首波或船尾流所導致的海浪波,是否應該可以在雷達屏幕上看到呢?一個反映到這些回波的雷達畫面,會否是一個沒有雜亂回波的雷達畫面呢?一個沒有雜亂回波的雷達畫面是一個可信的雷達畫面嗎?

Written by Bruce Chun

June 1, 2010 at 20:52

Posted in Radar Operation

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