Longitude Error Table (On 96 Nm Range Scale - Furuno FAR-28 Series Operator's Manual

APPENDIX

4. Longitude 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
62°N
60°N
135°E
Distance error in direction of longitude due to latitude
AP-46
Cursor position
indicated
139°E
Real cursor position
°N
96 nm
θ
LAT
OS position
R: Error
Cursor position
indicated
°E