Furuno RP-250 manual Longitude Error Table on 96 nm range scale

6. OTHER PLOTTER FUNCTIONS

6.2Longitude Error Table (on 96 nm range scale)

The longitude lines concentrate on the north pole and south pole, namely, 1 nm is equivalent to 1 minute at 0 degree latitude, 2 minutes at 60 degrees latitude, 3 minutes at 70 degrees latitude and so on. For this reason, a longitude error occurs on the radar display. For example, when own ship is at 60° N and 135° E, even if the cursor indication is 62° N and 139° E, the real cursor position is deviated to the left (west) side. The table below shows the longitude error, represented from 0° to 90° at 96 nm from the radar center (own ship).

Real cursor position		Real cursor position
62° N	° N	R: Error
Cursor position		Cursor position
indicated		indicated
		96 nm
		θ
60° N	LAT	E

135° E 139° E OS position

Distance error in direction of longitude due to latitude

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