There are 3 different options for selecting the Contrails you want to see by ticking the appropriate box.

1) In Chart Options:

a) Contrail on local data only

b) Contrail on Shared data

2) Contrail for single or other specific aircraft in aircraft list: Open Aircraft position report (APR)

a) from the chart by right clicking on aircraft or

b) from the aircraft list by Ctrl-right clicking on that row.

Length and width settings. Adapted from a message by Bev in the PlanePlotter group

Control parameters

The Options..Chart..Options dialogue has a Contrails panel which includes a section of parameters for the contrail that can be plotted behind each aircraft symbol.

The section includes the Length of the contrail and that has two parameters : the length in Seconds and the length in Steps (points).

So if you want a contrail that is five minutes long you would insert 300 in the sec box and if you want there to be 50 sample points along that contrail, you would put 50 in the steps box.  In that example, you can see that points in the contrail would be 6 seconds apart.  The screenshot above shows a length of 500 seconds (just over 8 minutes) with 50 steps, so 10 seconds per step.

Performance difference between Local and Shared aircraft

However, you need to bear in mind that it cannot invent points if there is no new data within that time interval.  If, for example, the aircraft is not being received locally, but is being received by sharing, there will only be new position reports in the contrail every minute, so you won't get a smooth curve for an aircraft that is turning.

If you are receiving the aircraft directly, and the signal is strong, you will probably be getting position reports every second or so and in that case, the contrail will be smooth unless you have a very large seconds/steps ratio, in which case it will not be smooth as the recorded points are that many seconds (seconds/steps) apart.

I am sorry it is not clear in the Help file but I suppose having created it, it seemed self evident without needing further explanation.

[I think all programmers suffer from this - I know I do - DJT]

What are "GES colour" and "alt colour"?

Alt colour - Altitude Colour - colour the contrails according their altitude

GES = Ground Earth Stations [Inmarsat] - the regions covered by each satellite are shown below:

(Thanks John Locker for that).