VISUAL PASSAGE PLANNER
Digital Wave

Pilot charts are a compilation of recorded weather observations dating back to 1850. Thousands of voyage logs were collated by Navy Lt. Matthew Fontaine Maury into graphic presentations of wind and weather which sailors could use for planning. They are still in print today, and still include much of the information Maury found.

The National Imagery and Mapping Agency (NIMA) publishes five large format color atlases of pilot charts covering the world. In these, the wind roses, which indicate the percentage and average velocity of winds from 8 directions, are considered the most important. Other information, such as percentage of gales, average wave heights and currents, air and water temperatures and recommended routes are valuable also.

The databases underlying these pilot charts are ideal for computer presentation. For instance you can convert the graphic data view from the 5 degree lat/long blocks of the paper charts, to the one degree resolution used in the original data. You can also change the standard Mercator chart projection to a more realistic spherical view and spin the image like a globe.

You can switch on and off weather data and other features like port and country names. Zoom in to get greater detail on the 1:1,000,000 vector chart. You can also program a route and see the wind and wave conditions you would expect to find on it. By building a simple "vessel speed profile" (much like a polar diagram for boat performance), the program can estimate leg speeds and even try to optimize the route.

It must be remembered that the routes are based on average monthly weather observations, and that the data is based on reports filed from 1850 to 1974. It is also "biased towards favorable weather conditions", since ships tend to avoid areas of bad weather. If you are planning to go to areas like 55°S and 125° W, you won't find much data.