Xplage enables the conversion of X-Plane datagrams into Google Earth "moving map" displays.
Xplage is an impressive software utility that serves as a specialized listener on IP networks. It listens for UDP datagrams that represent the geographical coordinates of the simulated flight path shown in the X-Plane flight simulator. After collecting these datagrams, it transforms them into a sequence of KML files that are regularly updated. By ingesting these files, Google Earth displays "moving map" views.
Xplage generates two KML files that serve different purposes, both of which can be customized by the user. The first KML file represents an overhead map with North at the top and an icon in the center of the satellite image which indicates the position of the simulated aircraft. The icon is centered by shifting the map in the direction of the flight path every time the file is refreshed.
The second KML file showcases a perspective view of the terrain in front of the simulated aircraft. In this view, the orientation of the airplane's pitch and roll is taken into account to update the perspective continuously. The user can adjust the refresh cycle so that both KML files update at intervals of their choosing.
It's important to note that because the refresh rates of Google Earth and Xplage are asynchronous and independent, the moving map images may lag slightly behind the actual position of the simulated aircraft. The effect can be that the images represent still snapshots that capture the position of the airplane shortly before they are displayed. This delay can be compounded by the intervals specified for refreshing the KML files, as well as delays in fetching satellite imagery from Google's servers over the public internet.
Xplage isn't a trivial program, but its structure is easy to comprehend once you have a good understanding of it. To use Xplage, the user needs to execute the software and set up a UDP socket to listen for incoming X-Plane datagrams. After setting up the socket, three asynchronous lightweight child processes are launched. They respectively wait for incoming datagrams from the simulator, an interval for KML output file updating, or a manual interrupt from the user. When the user decides to exit, they issue a request to the interrupt thread, and all four processes will be terminated.
Xplage generates two KML files that serve different purposes, both of which can be customized by the user. The first KML file represents an overhead map with North at the top and an icon in the center of the satellite image which indicates the position of the simulated aircraft. The icon is centered by shifting the map in the direction of the flight path every time the file is refreshed.
The second KML file showcases a perspective view of the terrain in front of the simulated aircraft. In this view, the orientation of the airplane's pitch and roll is taken into account to update the perspective continuously. The user can adjust the refresh cycle so that both KML files update at intervals of their choosing.
It's important to note that because the refresh rates of Google Earth and Xplage are asynchronous and independent, the moving map images may lag slightly behind the actual position of the simulated aircraft. The effect can be that the images represent still snapshots that capture the position of the airplane shortly before they are displayed. This delay can be compounded by the intervals specified for refreshing the KML files, as well as delays in fetching satellite imagery from Google's servers over the public internet.
Xplage isn't a trivial program, but its structure is easy to comprehend once you have a good understanding of it. To use Xplage, the user needs to execute the software and set up a UDP socket to listen for incoming X-Plane datagrams. After setting up the socket, three asynchronous lightweight child processes are launched. They respectively wait for incoming datagrams from the simulator, an interval for KML output file updating, or a manual interrupt from the user. When the user decides to exit, they issue a request to the interrupt thread, and all four processes will be terminated.
What's New
Version 2008-06-02: N/A