Furuno FR-1710 Measuring the Range, Measuring Bearing, Measuring range by the fixed range rings

1.18 Measuring the Range

Measuring range by the fixed range rings

Use the fixed range rings to obtain a rough estimate of the range to a target. They are concentric solid circles about own ship, or the sweep origin. The number of rings is auto- matically determined by the selected range scale and their interval is displayed at the upper-left position of the screen. The fixed range rings may be turned on/off and their brilliance adjusted with the [RINGS] key.

0.55NM

15.0°R

Range and bearing to cursor

Target

Ring interval

	Cursor
	No. 1 VRM
	(dotted)
	No. 2 VRM
	(dashed)
Active marker is	VRM
	0.375NM
circumscribed.	0.550NM
	Range to
	Range to No. 1 VRM
	No. 2 VRM

Measuring range by the variable range marker (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 circumscribed.

2.Rotate the VRM rotary control clockwise or counterclockwise to align the active VRM with the inner edge of the target of interest and read its distance (unit: nm) at the lower-right corner of the screen. Each VRM remains at the same geo- graphical distance when you operate the [RANGE] key. This means that the appar- ent radius of the VRM ring changes in proportion to the selected range scale.

3.Press the [VRM OFF] key to erase each VRM.

Figure 1-15 How to measure

range by VRM

1.19 Measuring Bearing

Use the Electronic Bearing Lines (EBLs) to find bearing of a target. There are two EBLs, No.1 and No.2, which are toggled by suc- cessive presses of the [EBL ON] key. Each EBL is a straight dashed line extending out from the own ship position up to the circum- ference of the radar picture. The fine dashed line is the No.1 EBL and the coarse dashed one is the No.2 EBL.

1.Press the [EBL ON] key to display either of the EBLs. Successive presses of the [EBL ON] key toggle the active EBL be- tween No.1, No.2 and index lines (if dis- played) and the currently active EBL readout is circumscribed.

2.Rotate the EBL rotary control clockwise or counterclockwise until the active EBL bisects the target of interest, and read its bearing at the lower-left corner of the screen.

3.Press the [EBL OFF] key to erase each EBL.

The EBL readout is affixed by “R” (relative) if it is relative to own ship’s heading, or “T” (true) if it is referenced to the North, as determined by the item EBL/VRM on the OTHER menu.

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