[Flightgear-users] Problems with autopilot and fix.dat

[Paul G. <gk...@co...>]

Hello All,

I wrote about 4 weeks ago about a "problem" I'd encountered in fix.dat, 
specifically that there are many duplicate waypoints with vastly different 
coordinates. I cited as an example CAT05, located both in El Salvador and in 
Sicily...

I received a response from a friendly fellow who has a copy of the most recent 
DAFIF data. These are the data which are 'cooked' down into, among others, 
fix.dat. He sent me a clip showing how the original data 'names' several 
fixes with different names, but 'identifies' them identically. Unfortunately, 
the process of 'cooking' the data eliminates the waypoint names (which 
identify each waypoint without duplication) in favor of the waypoint 
identities (which results in many duplicates) in the resulting fix.dat file 
which is used by FGFS's autopilot waypoint selector.

He also said that he uses a perl script to work around the duplicates by 
selecting the one that is closest to wherever he is. However, it seems that 
the waypoint code is not so clever, as it consistently seems to select the 
last of a series of identical waypoints (as listed in fix.dat), regardless of 
which is closest to where you are (or the last waypoint in a list that you 
are compiling, as applicable).

I worked around this by 're-identifying' the western-hemisphere duplicates by 
inserting a '1' after the letters (e.g., "CAT05" becomes "CAT105"). However, 
I view this as a strictly temporary workaround (although FGFS cheerfully 
accepts 6-character waypoint IDs, it violates the official 5-character 
convention). I would prefer to see a better solution (a la Mr. Anderson) 
built into the autopilot waypoint selection code, or an option to allow the 
user to select one from a list, or put up a list while auto-selecting the 
closest (particularly if two identically ID'd waypoints are equidistant +/- 
some configurable number of miles)...

(on a side note, I'd like to see all text inputs converted to all-caps (as 
appropriate) so that a keyboard entry of "cat05" will match 
fix.dat's "CAT05", but that's another issue...)

So with all that said, I've looked at the list of maintainers, and I am unsure 
which I should contact as there are many who've had their hand in the 
autopilot code. Who should I be talking to about my concerns, ideas, etc.?

Paul Glanville