Determining Actual Radar Range - Raymarine RL70C Owner's Handbook Manual

Chapter 3 Standard Radar Operations
Maximum
Range (nm)
1 /
¼
½
¾
1½
3
6
12
24*
48*
72*
* The maximum range depends on your scanner type, as detailed in the Pathfinder Radar
Scanner Owner's Handbook.
The number of range rings shown in the table is the number to the selected
range. Additional range rings are displayed to the edge of the radar picture, at
the standard ring interval for the current range, and are most noticeable when
the centre is offset.

Determining Actual Radar Range

The actual maximum radar range is essentially line-of-sight, and is limited by
the height of the scanner and the height of the target as shown in the following
diagram. The table below lists some range examples:
Antenna Height
3m
3m
5m
5m
Note: The ranges shown in the table are theoretical maximum ranges. The
radar horizon is greater than the optical horizon, but the radar can only detect
targets if a large enough target is above the radar horizon.
Number of
Range Rings
2
8
2
4
3
6
6
6
6
6
6
6
a
1
Radar
R max = 2.23 (
R max maximum radar range
h radar antenna height
H target height
R max = radar horizon of antenna (
Target Height (m)
3m
10m
3m
10m
Range Ring
Interval (nm)
1 /
16
1 /
8
1 /
8
¼
¼
½
1
2
4
8
12
R max
a
2
Earth
h + H )
in nautical miles
in metres
in metres
a a
) + radar horizon of target (
1 2
Maximum Range (nm)
7.8
10.9
8.9
12.0
53
Cliff
)
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