Serge, see - Is there a way to make it clearer?
Route & Mark Manager | Official OpenCPN Homepage
The overall planned speed for the route. The speed for each leg can be set by going to the waypoint Properties->Description tab for the waypoint that starts the leg, and write in the speed. For example " VMG=9.7". [Unfortunately this approach presently excludes writing descriptions for the waypoint. One or the other, be warned!] The Plan Speed value is persistent and will be used for further routes, unless changed. The default value is 6.0 knots.
Leftbrain, I believe it is just a value, not calculated at present. Sean's plugin weather_routing used to calculate hull
speed accordingly, and make an estimated polar from boat
, sail area etc. That has been simplified to just use polar files, but Sean would still have the code available.
The waypoint & route
properties should be expanded at some point to accommodate an average speed for each leg, IMHO without affecting the ability to have a description. However I have not used this feature much, but others do use it extensively.