Furuno GD-280, Руководство оператора

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11-9
11.4.3 Erasing the heading line, north marker
The heading line is a line from the own ship position to the outer edge of the radar display area
and appears at zero degrees on the bearing scale in head-up mode, and in the north-up and true
motion modes it changes with ship's movement.
The north marker appears as a short dashed line. In the head-up mode the north marker moves
around the bearing scale. In accordance with compass signal.
To temporarily extinguish the heading line and north marker to look at targets hidden by them,
press the [GAIN] control. The heading line and north marker reappear when the control is
released.
North Marker
Heading Line
11.4.4 Zoom
The zoom function enlarges an area of interest as large as twice the normal viewing. Note that
the zoom feature is inoperative when the display is off centered or the mode is true motion or
course up.
1. Place the +cursor close to the point of interest by operating the trackball.
2. Press the [ZOOM] key. The area around the +cursor and own ship is enlarged twice as large
as the original size and the label ZOOM appears at the lower-right corner of the screen.
3. To cancel zoom, press the [ZOOM] key again.
Note: Zoom is canceled whenever the range or mode is changed.
11.4.5 Echo stretch
On long ranges target echoes tend to shrink in the bearing direction, making them difficult to see.
On short and medium ranges such as 1.5, 3 and 6 nm scales, the same size targets get smaller
on screen as they approach own ship. These are due to the inherent property of the radiation
pattern of the antenna. To enhance target video, use the echo stretch function. There are two
settings: echo stretch 1 (ES1) to enlarge in bearing direction for long range detection, and echo
stretch 2 (ES2) to enlarge in both bearing and range directions.
The echo stretch magnifies not only small target pips but also returns (clutter) from sea surface,
rain and radar interference. For these reasons make sure these types of interference have been
sufficiently suppressed before activating this function.