16-1
16. RADAR OVERLAY
16.1 Introduction
The radar overlay has the radar echo image overlaid on the ECDIS chart display, in
the Voyage navigation mode. The radar video signal can be fed from a FURUNO radar
connected to the ECDIS via LAN, or via the optional Radar Connection Box (RCB-
002) in the case of a FURUNO radar or a non-FURUNO radar.
This ECDIS has many features to support exact match in scale and orientation of the
chart and radar echo image. Exact match of the radar echo image and chart is an es-
sential security feature. If the radar echo image and the chart display match, then the
mariner can rely on what he sees and the mariner also gets a very good confirmation
that his navigation sensors (such as gyro and position fixing equipment) operate prop-
erly and accurately. However, if the mariner is unable to achieve exact match, it is a
very strong indication that something is wrong and he should not rely on what he sees.
If a radar echo and a chart object occupy the same geographical position, the one se-
lected as having priority (with [Priority] on the [Echo] page in the [Overlay/NAV Tools]
box) is displayed.
Selected scale of displayed chart also defines scale of radar overlay. When you
change the chart scale, the scale of the radar overlay is automatically changed. The
table below shows the standard scale and equivalent radar range.
Radar
range (nm)
Standard
scale
Radar
range (nm)
Standard
scale
0.25 1:4,000 6 1:90,000
0.5 1:8,000 12 1:180,000
0.75 1:12,000 24 1:350,000
1.5 1:22,000 48 1:700,000
3 1:45,000 96 1:1,500,000
Radar
echo
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