Changelog 2016.4: Difference between revisions

* new [[File_Formats#.2A.stg_files|STG verbs]] <ref>https://forum.flightgear.org/viewtopic.php?f=5&t=22809&p=295366#p295342</ref>

* For years, FlightGear has been reading a large file called apt.dat.gz and located in [[$FG_ROOT]]/Airports. This file, which is maintained in collaboration with the X-Plane developers and users<ref>Via [[WorldEditor]] and the [https://gateway.x-plane.com/ X-Plane Scenery Gateway].</ref>, contains a lot of information about airports (names and geometry of runways, taxiways, aprons, surface type, position of runway thresholds, light beacons, position of Control Tower, communication frequencies... even startup locations, though FlightGear reads parking positions from other files called ''airportID''.groundnet.xml). Data from this file is used to create the scenery files for airports (.btg.gz), to display airports in the FlightGear built-in map, as well as to let the simulator know how to place your aircraft when starting on a runway—among others.

: Despite the possibility to have FlightGear read portions of the scenery from various folders (cf. [[$FG_SCENERY]]), this data was only read so far from this one file, [[$FG_ROOT]]/Airports/apt.dat.gz. As a consequence, custom sceneries could not bring new or updated airport layouts without FlightGear having part or all of the information wrong concerning these airports, since it was read from a file that is maintained independently from said custom sceneries—and tied to FlightGear's current World Scenery, and therefore frozen in FlightGear since 2013.

: This problem is solved in FlightGear 2016.4,<ref>{{cite web

   }}</ref> which reads files following the pattern NavData/apt/*.dat or NavData/apt/*.dat.gz inside each scenery path, when they exist. These files, collectively called ''apt.dat files'', should have the same syntax as [[$FG_ROOT]]/Airports/apt.dat.gz, and are the natural output of [[WorldEditor]], the recommended tool to create or update airport layouts. With this change, each custom scenery can now embed its own apt.dat files that describe the airports shipped in the custom scenery; FlightGear 2016.4 and later will read them.

: The precedence order for these files is the same as for [[$FG_SCENERY]]: if the same airport appears in several apt.dat files, only the first definition found in $FG_SCENERY order is used.<ref>And for apt.dat files belonging to the same component of [[$FG_SCENERY]], the first file in lexicographic order takes precedence, although in practice this rule shouldn't be needed (why ship several definitions for the same airport inside a given [[$FG_SCENERY]] component?).</ref> Finally, for compatibility with existing scenery and as a fallback measure, the traditional [[$FG_ROOT]]/Airports/apt.dat.gz file is still read by FlightGear, with lowest precedence.