Jeppesen Marine Workboat Navigator 1.3 - Manual (Page 52)

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Jeppesen Workboat Navigator User’s Guide
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Chart Data
Distance Markers
Distance Markers (also known as Mile Markers or River Marks) are some of the
most useful aids on a river. Typically, a Distance Marker is a physical object on
the river attached to a beacon or in other easily seen locations. Distance Markers
indicate units of statute miles, the unit of measurement on the United States
Western Rivers System.
With the exception of the Ohio River, Distance Markers indicate the distance
upstream from the mouth of a river. Ohio River Distance Markers start at the
headwaters and indicate the distance downstream.
On vector charts, Jeppesen Workboat Navigator includes a graphic representation
of each Distance Marker, along with a digital display in the NavInfo window pane
that includes the River Name and Distance Marker you are closest to.
Figure 5.2 - River Mark Position in the NavInfo Window Pane
How close you are to a Distance Marker, as displayed in the NavInfo window pane,
is determined from your triangulated position between two Distance Markers at any
given time.
In some cases, Distance Marker locations are not exact. When the Distance Marker
(River Mark) is shown with an asterisk (mile*) in the NavInfo window pane, the
mileage shown is an approximate number, not an exact number.