22. Radar Overlay; Introduction - Furuno FEA-2107 Operator's Manual

22. Radar Overlay

22.1

Introduction

The radar overlay is optionally available. This means that the radar echo image can be output from the radar unit and
shown on the ECDIS chart display.
Radar overlay video can be received by two methods by ECDIS:
1. Through Radar overlay card fitted in the ECDIS
2. Through LAN from FAR-2x07 Radars, which are capable to send radar video to LAN
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 essential 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 receivers) operate properly 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.
This ECDIS can use radar echo image in several user selectable modes. The "ECDIS only" mode operates without
the radar echo image. The "ECDIS and radar" mode operates using rules for the type-approved ECDIS to visualize
the radar echo image. The "radar over chart" mode draws radar echo image on top of the chart. This mode should
only be used temporarily because legally the equipment is not an ECDIS which can legally replace paper chart when
operating with "Radar over chart". The "radar video only" mode should only be used temporarily to check radar
echo presentation, because the equipment is not an ECDIS which can legally replace paper chart when operating
with the "radar video only" mode.
The radar echo image is output directly from the radar transceiver so the range used in a connected ARPA radar
display does not change the scale in the ECDIS. This ECDIS is nearly independent of the ARPA radar display
settings. The only ARPA radar display setting which affects the radar echo image on the ECDIS is pulse length; the
ARPA radar display controls the radar transmitter and chooses the pulse length. All other controls such as Gain,
STC, FTC, interference rejector, echo stretch and echo trails may be controlled from the ECDIS.
Chosen 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 maximum range of the radar overlay is 24 nautical miles. Radar overlay
can be displayed even if the own ship is not located in the displayed chart area if the range is less than 24 nm.
The thumb rule for range of displayed area:
•
Chart scale 1:10,000 is almost equal to traditional radar range of 0.75 nm
•
Chart scale 1:20,000 is almost equal to traditional radar range of 1.50 nm
22-1