Eagle Electronics 1000C manual Map Datum Selection, 146

Map Overlays (Range Rings; Lat/Long Grid)

The map screen can be customized with four range rings and/or grids that divide the plotter into equal segments of latitude and longitude.

Range rings are handy for visually estimating distances on the map. The ring diameters are based on the current zoom range. For example: at the 100-mile zoom, the screen will show two rings with your current position in the center. The large ring touching the left and right sides of the screen is 100 miles in diameter (same as the zoom range). The second smaller ring is 50 miles in diameter (always 1/2 the zoom range).

The distance from your current position to the smaller ring (the ring's radius) is 25 miles (always 1/4 the zoom range). With the arrow keys and map cursor, you can scroll the map to see the third and fourth rings. In this example, the distance to the third ring is 75 miles and distance to the fourth ring is 100 miles from your current position.

To set range rings: From the Map Page, press MENU↓ to MAP DATAENT. Press ↓ and → to RANGE RINGS. With the option highlighted, press ENT to check it (turn on) and uncheck it (turn off.) After the option is set, press EXITEXIT to return to the page display.

To set Lat/Long Grid: From the Map Page, press MENU↓ to MAP DATAENT. Press ↓ and → to LAT/LON GRID LINES. With the option highlighted, press ENT to check it (turn on) and uncheck it (turn off.) After the option is set, press EXITEXIT to return to the page display.

Map Datum Selection

Maps and charts are based on a survey of the area that's covered by the map or chart. These surveys are called "Datums." Maps that are created using different datums will show the same latitude/longitude in slightly different locations.

All datums are named. The GPS system is based on the WGS-84 datum, which covers the entire world. Other datums may also cover the entire world, or just a small portion of it. By default, your unit uses the WGS-84 datum. It, however, can show your position using one of 191 different datums. To change the datum:

1.Press MENUMENU↓ to GPS SETUPENT↓ to DATUM SELECTIONENT.

2.Scroll ↓ or ↑ to select the desired datum, then press ENT.

3.To return to the last page displayed, press EXITEXIT.

A list of the datums used by this unit is in the back of this manual.

146