Furuno FR-8252 Measuring the Range to a Target, Measuring range by the variable range marker VRM

1. OPERATIONAL OVERVIEW

1.16Measuring the Range to a Target

The range to a target may be measured three ways: with the fixed range rings, with the cursor (if set to measure range and bearing), and with the VRM.

Use the fixed range rings to obtain a rough estimate of the range to a target. They are the concen- tric solid circles about own ship, or the sweep origin. The number of rings is automatically deter- mined by the selected range scale and their interval is displayed at the upper-left position of the screen. Count the number of rings between the center of the display and the target. Check the range ring interval and judge the distance of the echo from the inner edge of the nearest ring.

1.16.1Measuring range by the variable range marker (VRM)

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 key to display either of the VRMs. Successively pressing the VRM key toggles the active VRM between No. 1 and No. 2. The currently active marker is enclosed with >.....< in the VRM indication box.

2.Operate the Trackball to align the 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 RANGE key. This means that the apparent radius of the VRM ring changes in proportion to the selected range scale.

3.You may “anchor” the VRM by choosing it and pressing the ENTER key.

4.To erase a VRM, make it active and press the CANCEL/HL OFF key.

No. 1

VRM

+ 37.4°R 0.007 NM

+ Target

No. 2

VRM

VRM1>0.007NM<	VRM
VRM2 0.140NM
	indications

Measuring range and bearing between two targets with the EBL

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