Determine the launch method

[corstian]

In order to collect a key piece of information we're going to determine one of three launch methods;

• Winch
• Aerotow
• Self start

Each launch method has its own characteristics;

• Winch launch: A winch launch is determined by a steep climb (skewed z curve) over a short and straight distance (1-2 kilometers), followed by free flight which is characterized by a much more volatile amount of available energy.
• Aerotow: A primary characteristic of an aerotow is that there are two aircraft closely departing in line. The flight path is characterized by a much longer climb, after which it's climbrate should lower.
• Self launch: Somewhat similar to an aerotow, but with only a single aircraft.

Elimination process

To make the process of determining the launch method a bit easier we'll try to eliminate certain options;

1. Check if it is not a winch launch. This can be determined by the climb profile.
2. Check if there is another aircraft flying in front. If this is the case, automatically tag it as an aerotow. (The interpolation algorithm might be greatly beneficial to solve this)
3. If both options above are not the case; tag it as being a self launch.

Regardless of launch method it would be important to determine the end of the launch. This should be done by checking the flight profile. XCSoar should have an algorithm for this baked in.

[corstian]

Current status:

• There is about 95% accuracy when recognizing an aerotow launching from a position which can be observed by a receiver.
• Winch launches and self launches are not so accurate yet. Need to create a stronger distinction between both
• Launches from positions not covered by receivers (outside direct line of sight) require more attention as recognition of those is flakey at best.

[corstian]

With the recent release, the launch recognition is shakey at best. Will be addressed in the next release.

[pschuler78]

Motor aircrafts seems to be detected as Winch launch. Using the aircraft type could improve detecting the launch method.

[corstian]

I need to move some other work out of the way before I have the time to dive into this, but here are a few ideas on how this can be improved in the future;

1. The best solution would be to improve the recognition to define it as being a 'self' launch.
2. The second best, but eventually implemented either way would be an accessor (just like the nearbyAirfieldAccessor) to retrieve aircraft information.