Incorrect Wind Direction Indication

[mhoogerland]

I've noticed that the wind indication in the Isaac software seems to be incorrect, at least in group rides. This past Saturday, the wind was from the south to begin and swung around to the Southwest and then West-Southwest during the time of the ride. We rode south, then Southwest for the first half of the ride before turning north/northeast to return. the attached graph seems to show a tailwind throughout most of the ride.

Am I incorrectly reading the graph?

Wind Direction Graph.PNG (53.72 KiB) Viewed 2487 times

[Velocomp]

You are reading the wind graph correctly; it shows that most of the time you are in a tailwind.

How can this be? You provide the answer in your post: you are riding in a group. When you're in a group and not at the front of the line, you are drafting behind the other people in front of you. The cyclists ahead of you are pushing the wind in the direction of the ride, creating a total wind speed that is less than bike speed. When wind speed is less than bike speed, that is a tail wind.

Your graph shows something else, too. There are a few places where your wind speed is comparable to bike speed. For example, look at the 6th "box" from the beginning. What happened there? You were at the head of the line, pulling the group forward!