Appendix 2 Longitude Error - Furuno FAR-1416 Operator's Manual

APPENDIX 2 LONGITUDE ERROR

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 er-
ror, represented from 0° to 90° at 96 NM from the radar center (own ship).
Real cursor position
62°N
60°N
135°E
q
5° 10°
LAT
75°
0.2256 0.4444
70°
0.21980213 0.43290201 0.632803
65°
0.21229339 0.41810678 0.61115946 0.78556318 0.93600295 1.05790007 1.14755221 1.20224625 1.22034042
60°
0.20316898 0.40012949 0.58486463 0.75173456 0.89565021 1.0122297
55°
0.19249832 0.37910698 0.55411863 0.71218478 0.84848102 0.95885565 1.03998717 1.08933651 1.10552105
50°
0.18036264 0.35519924 0.51915545 0.66721485 0.79485438 0.89818413 0.97406698 1.02021439 1.03525547
45°
0.16685429 0.32858822 0.48024119 0.61716701 0.73517843 0.83067689 0.90076355 0.94332783 0.95711098
40°
0.15207608 0.29947644 0.437672
35°
0.13614047 0.26808546 0.39177186 0.53339693 0.59953781 0.67725844 0.73420069 0.76865661 0.77961957
30°
0.11916876 0.2346542
25°
0.10129001 0.19943707 0.29139874 0.37433139 0.44568053 0.50326182 0.54532952 0.57063015 0.57843983
20°
0.08264056 0.16270211 0.23768966 0.30527334 0.36336372 0.41017869 0.44429984 0.46471615 0.47085389
15°
0.06336208 0.12472888 0.18217162 0.23389198 0.27828148 0.31397386 0.33988878 0.35526538 0.35968447
10°
0.04360137 0.0858064
5°
0.02350833 0.04623087 0.0674093
0°
0.00323737 0.0063035
q
50° 55°
LAT
75° 1.2780 1.2192
70° 1.24442563 1.18701379 1.09356117 0.96694117 0.81103484 0.3061092
65° 1.20131324 1.14577786 1.05546143 0.93315023 0.78260251 0.60843159 0.41596331 0.21107193 0
60°
1.14905813 1.09582188 1.00932899 0.89225746 0.74821409 0.58162173 0.397582
55° 1.08805799 1.03752602 0.95551494 0.84457408 0.70813132 0.55038538 0.37617487 0.19082831 0
50° 1.0187708 0.97133397 0.89442885 0.79046297 0.66265924 0.51496026 0.35190481 0.17848659 0
45° 0.94174265 0.89774948 0.82653562 0.73033596 0.61214392 0.47561599 0.32495654 0.16478648 0
40° 0.85754099 0.81733258 0.75235195 0.66465066 0.55696981 0.43265198 0.29553516 0.14983224 0
35° 0.76681293 0.73069528 0.63744242 0.59390696 0.49755683 0.38639524 0.26386458 0.13373769 0
30° 0.67024897 0.63849695 0.58741521 0.51864327 0.43435714 0.33719779 0.23018583 0.11662531 0
25° 0.568584 0.54143927 0.49791741 0.43943239 0.36785173 0.28543407 0.19475522 0.09862535 0
20° 0.46259176 0.44026091 0.40463016 0.35687717 0.29854675 0.23149802 0.15784242 0.07987479 0
15° 0.35307892 0.3357319
10° 0.2487894 0.22864776 0.20955062 0.18426754 0.15366517 0.1187643
5° 0.12684572 0.11982348 0.10624302 0.09552679 0.0791912
0° 0.01184713 0.01008727 0.008104
AP-12
°N
Cursor position
indicated
LAT
139°E
15° 20°
0.6496 0.8350 0.9950
0.8134132 0.96923215 1.09551918 1.1884382
0.56242216 0.66990732 0.7568477
0.3428901 0.44054055 0.52460545 0.59251483 0.6422089
0.12526714 0.16073056 0.19108136 0.21537949 0.23289096 0.24311083 0.24577764
0.08634588 0.10242699 0.11514595 0.1241207
0.00903844 0.01130406 0.01299309 0.01403609 0.0144058
60° 65°
1.1233 0.9933 0.8332
0.30826343 0.2716059 0.22696965 0.17580013 0.11972833 0.06051633 0
0.00605903 0.00411455 0.00111154 0.00111154 0.00028325 0
Real cursor position
96 NM
q
OS position
25° 30°
1.1248 1.2202
1.09793265 1.15016811 1.16737294
0.82060477 0.85926197 0.87168229
70° 75°
0.6479 0.4431
0.43117887 0.21881975 0
0.08070304 0.0406973
0.04106355 0.04106355 0.02056855 0
R: Error
Cursor position
indicated
°E
35° 40° 45°
1.2786 1.2980
1.24517456 1.26402037
0.67220131 0.68162348
0.12910605 0.13000029
0.0141187 0.01323356
80° 85°
0.2249 0
0.20171772 0
0
(NM)
(NM)
90°