AI Traffic: Difference between revisions

Next, start editing all the relevant startup location parameters. Parking heading can be changed by dragging the little red circular heading indicator. The parking space's radius can be changed by clicking anywhere on the big red circle. Then you can change the parking space's radius by dragging the mouse. Although this usually works for setting up a rough draft, these parameters can directly be changed in the properties dialog. If the properties dialog is not visible, press [ctrl-p] to bring it up. It is possible to select multiple startup locations by pressing the shift key while selecting, and the parameters for each selected startup location can be changed at the same time. This is a powerful feature for editing the parameters of a whole series of parking locations, and also for equating and orienting gate radius and heading.  

Holding points are nodes in the network that do something special. They can be used by FlightGear to make traffic wait at certain specific locations. As a matter of fact, the 'normal' and 'Cat II/III' hold points are not yet used by FlightGear, but are part of the development plan. Currently, hold points are implicitly assigned by the FlightGear AI code. For instance, traffic waiting for takeoff clearance is holding at the first point before the runway. Likewise, traffic can receive a hold position instruction just before an intersection in the taxiway system, when traffic is approaching at the other leg. While these implicit hold points work reasonably well, there are some limitations. Consider for example runway 07 at CYYC (Calgary Intl, Canada). In the FlightGear rendition of this airport, there are no taxiways leading to this runway, so departing aircraft should back track down the runway from an entrance point at the middle of the runway. Currently that point will also become the runway entrance holding point. This is clearly undesirable, because it means that traffic is actually waiting ''on the runway'' in order to get clearance to enter it. For this reason, airport ground network designers should have a means to have explicit control over holding points. The normal hold point is meant for just that.

=== Editing the startup location parameters ===

Once you have created a ground network, you'll find that it probably won't work yet in FlightGear. The main reason for this is that the default gate size is set fairly small, and most aircraft won't fit into the assigned space. Therefore, you need to edit the parking space parameters. In addition, you also need to give each parking space a name, and a heading, and probably an airline code. Changing name, and heading can be done in TaxiDraw, by right clicking on the startup location. This will bring up a dialog, in which you can change latitude, longitude, heading, and name. Once you're done editing, click okay to accept the new values, or cancel to discard.

 

Editing the startup location radius, type, airlineCodes, and pushBack parameters is not yet possible in TaxiDraw. So changing these requires saving the project and editing these using a text editor. Once you save the project, this will be done in a file [filename].tpj (TaxiDraw project). The ground network will be saved in a file named [filename]-groundnet.xml, which will be in the same folder as where you saved the project.

 

You can edit the remaining parameters by loading this groundnet.xml file into a text editor. Once you are done editing make sure you import these changes into TaxiDraw immediately. Do this by going to [File| Import FlightGear AI Network]. This will open a file selection dialog. Choose the file you just edited and click okay. TaxiDraw will ask for confirmation to overwrite existing ground network data and confirm this by clicking on "yes".

=== Copying the ground network into FlightGear's scenery directory ===

Finally, once you have finished creating a groundnet project, you can test it in FlightGear. Create a directory in your <tt>[[$FG_SCENERY]]/Airports/[I]/[C]/[A]/</tt> directory, with the three first letters of the ICAO code of your airport. For example <tt>[[$FG_SCENERY]]/Airports/E/H/A/</tt>. Next, locate the file [filename]-groundnetwork.xml and copy this to the directory you just created. Finally, rename the file you just copied to <tt>[ICAO].groundnet.xml</tt>.