Measuring Range And Bearing To A Target - Furuno GP-280 Operator's Manual

11.5 Measuring Range and Bearing to a Target

This section shows you how to measure the range and bearing to a target.
11.5.1 Measuring range
Measuring range with the range rings, +cursor
Use the fixed range rings or +cursor to obtain a rough estimate of the range to a target. The
range rings are the concentric solid circles about own ship, or the sweep origin. The number of
rings is automatically determined by the selected range scale and their interval is displayed at
the upper-right position of the screen. For measurement by the +cursor place the +cursor on the
inner edge of the target. See the range to the cursor at the left side of the screen.
Measuring the range with the VRM
Use the Variable Range Markers (VRMs) for more accurate measurement of the range to a
target. There are two VRMs, No. 1 and No. 2, which appear as dashed rings so that you can
discriminate them from the fixed range rings. The two VRMs can be distinguished from each
other by different lengths of dashes.
1. Press the [VRM ON] key to display either of the VRMs. Successive presses of the [VRM ON]
key toggle the active VRM between No. 1 and No. 2 and the currently active VRM readout is
marked with >.
2. Turning the VRM control, align the active variable range marker with the inner edge of the
target of interest and read its distance at the lower-right corner of the screen. Each VRM
remains at the same geographical distance when you operate the
that the apparent radius of the VRM ring changes in proportion to the selected range scale.
Check the VRM range indication at the lower-right hand corner on the screen.
3. Press the [VRM OFF] key to key to erase each VRM.
Note: The unit of range can be selected to nautical miles, statute miles or kilometers. This can
be done on page 2 of the radar Initial Setting. For further details see page 11-33.
Range Ring
Target
Interval
+Cursor
No.1 VRM
(Dotted)
No.2 VRM
(Dashed)
〉 0.375NM ← No.1 VRM Range
0.550NM ← No.2 VRM Range
 〉  Active marker
, key. This means
11-11