I downloaded a grib file of oceanography (Mean Wave Period) from ERA-Interim and the longitude values give the value at the points is 0,1, 2, 3....357, 358, 359

If I have geographical coordinates that fall between the range 359 to 360 degree longitude. How can I represent them?

Thank you for your time and concern reading my question,



1 Answer 1


Remember that 360° == 0°. They're the same line of longitude. So the gap between 359° and 0° is no more than the gap between 1° and 2°, and should be handled the same way.

  • $\begingroup$ Hi Simon, so the value at 359.25 should be the same as the value at 1.25 ? $\endgroup$ Jun 19, 2019 at 13:57
  • $\begingroup$ @EwokTheSithLord no, the value at 359.25 is the same as the value at -0.75. Think of a line of equally spaced numbers through this region: 359.0, 359.25, 359.50, 359.75, 0.00, 0.25, 0.5.... does that help? $\endgroup$ Jun 19, 2019 at 14:58
  • $\begingroup$ Hi Simon, sorry to bother you again. But as I mentioned if the range is only from 0 to 359, I cannot guess the value at 359.25 (since -0.75 is not in this range) $\endgroup$ Jun 19, 2019 at 20:08
  • $\begingroup$ Remember that 360° is the same as 0°. You have information at 0°. If you need to know the value at 7.5°, you will probably interpolate between the values at 7° and 8°. If you need to know the value at 359.5°, you can interpolate between the values at 359° and 0°. It's no different. $\endgroup$ Jun 19, 2019 at 20:18
  • $\begingroup$ Thank you so much Simon, for the interpolation method, would you recommend cubic ? $\endgroup$ Jun 19, 2019 at 20:20

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