Furuno NAVNET 1823C - Manual (Page 97)

3. PLOTTER OPERATION
3-11
3.5.2 Indices and chart enlargement
When the [RANGE] key is operated, you will see several frames appear on the
chart. These frames are called indices and they show you what parts of the chart
can be enlarged in the current range.
Sample chart (Japan), showing indices
When a chart cannot be displayed
A chart will not be displayed in the following conditions:
• When the chart scale is too large or too small.
• When scrolling the chart outside the indices.
When this happens, select proper chart scale.
Note: Indices can be turned on or off. For further details see “Chart border line”
on page 5-14 for FURUNO and NAVIONICS charts and page 5-16 for
C-MAP charts.