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True winds (defined herein as a wind with a direction referenced to true north and a speed referenced to the fixed earth) are essential for oceanographic and atmospheric research over the ocean. Through analysis of automated wind data collected by WOCE research vessels, the analysts at WOCE-MET determined that large errors were common in true wind calculations. These errors were found to be the result of 1) confusion in the definition of true wind and the variables needed to calculate the true wind, 2) incorrect installation or recording of wind parameters, and 3) missing or incorrect navigation data. On this page we provide both documentation of the problems that occur in true wind computation (primarily with automated systems) and program source codes for computation of true winds using meteorological definitions. The meteorological true wind is defined as the generic true wind above with the wind direction being FROM which the wind is blowing. This is opposite the wind direction commonly recorded by oceanongraphers and different from the second Merchant Marine true wind direction, which is referenced to the ship's bow (See Table 1).

For details on the confusion in definitions and the problems found in wind and navigation measurements, please read "Establishing more truth in true winds". This article has been published in the Journal of Atmospheric and Oceanic Technology and contains information on:

Causes for inaccuracy Section 2
Vector calculation of true winds Section 3
Common problems found in true winds
           during WOCE-MET Quality control

Section 4
Estimating true winds from incomplete data sets Section 5
Summary and recommendations Section 6
Detailed mathematics for automated calculation
           of true winds

Appendix A
Conversions between meteorological, oceanographic,
           and Merchant Marine conventions

Appendix B

The calculations presented in Appendix A are the basis to a set of program codes available for calculating true winds (meteorological) from underway and on-station vessels. We provide the necessary subroutines and a test program in three common languages: FORTAN, C, and IDL (an Interactive Data Language). These programs have all been tested under the Silicon Graphics operating system. WOCE-MET believe the codes will be portable to other platforms, but no tests have been run. If you experience any problems using these codes, contact us at


C-Codes FORTRAN Codes IDL Codes

Any questions regarding the any of the above information should be sent to: