Frequently Asked Questions

• Did the airplane crash if it can no longer be found on this site?
• What should I do if the airplane is overdue?
• How does this technology work?
• What stations are tracked?
• For how long will position reports be available?
• How do I use Google Earth to "fly along" or play a tour of a track?

• Did the airplane crash if it can no longer be found on this site?


Probably not.  Most certainly not!

The most likely explanation is some sort of system failure.  In approximate order of likelihood:


The aircraft is not in an area of radio coverage.  This happens when the airplane is too low to reach the nearest ground station or is blocked by terrain or has a substandard antenna installation.


The mail2600.com server is (temporarily) down or the feed of position reports to it from the ground stations has been (temporarily) interrupted.


The pilot has turned off APRS tracking either on purpose (e.g. to use the tracker radio for voice communications) or accidentally (e.g. bumped a switch) or the tracker blew a fuse or . . .

• What should I do if the airplane is overdue?


Be sure you have given the airplane enough time to reach its original or an alternate destination.   Consider the possibility of a change in plans and flight for considerably longer than initially planned due to weather diversion or another reason (within the limits of the fuel on board).

Then you can accomplish these steps in sequence:


First, attempt to contact the pilot at his destination by cellphone or other means.


Next, contact another party at the intended destination and inquire on the whereabouts of the aircraft.  Contact any friends or family members that may know the location of the aircraft.


Finally, when you have exhausted all means to locate the aircraft, contact the FAA to report an overdue aircraft.   Once way to contact the FAA is by telephoning the Automated Flight Service at (800) WX-BRIEF (800-992-7433).   Ask for a "briefer".   Be prepared to give specific information about the aircraft's last known position, the pilot, and the pilots intentions.   Flight Service will initiate the Overdue Aircraft procedure.

• How does this technology work?


A combination of radio and TCP/IP communication is used.  The aircraft position and other parameters (as measured by an onboard GPS) are transmitted from the aircraft in real time to a network of amateur radio (ham) ground stations on VHF (the radio link).   The ground station(s) receiving the transmission forward it to a network of servers and they in turn feed it to this site's server (the TCP/IP link).

At this site, the server filters and parses the TCP/IP feed and the resultant parameters are used to populate a database of position reports.   The database is queried and displayed by a number of scripts running on a web server.   This is all done by a combination of Perl, MySQL, Javascript, and HTML running on a dedicated PC in my hangar, using my home broadband connection.

Other web sites (see the APRS Tracking Links on the sidebar at the left) also receive the same TCP/IP feed but populate and display their own databases.

The on-board equipment needed for tracking can cost from about $75 to over $200 and consists of the following:


GPS (often the aircraft GPS can be used instead of a dedicated one).


Transceiver.   An amateur radio transceiver capable of transmitting on 143.390 MHz at any power level (i.e. one watt is just fine).


Antenna,   An external vertically polarized antenna (such as a bent whip) is best but a " rubber dummy load " can give acceptable results.   Even an unused VHF NAV (VOR) antenna will work fairly well.   Generally, a horizontally polarized antenna in a poor location (such as a wingtip-mounted antenna in a Van's RV) will work somewhat but gives inferior results.


TNC or modem-like device (e.g. a "tracker") that converts the digital data from the GPS to audio tones transmitted by the transceiver.  One low cost device is the Byonics TinyTrak3.


This device is an all-in-one-box, turnkey solution for $229.   It consists of a Tracker2 model T2-301 and a VHF radio in a small steel enclosure.   It does require a connection to the aircraft GPS or its own dedicated GPS.  



This device is another all-in-one turnkey solution ($190).   It also requires a GPS input.  

• What stations are tracked?


All airborne APRS stations in the continental USA, Alaska, and Canada transmitting either the small airplane or large airplane symbol are tracked.   Also, the station must use a valid US or Canadian ham callsign or aircraft registrtion number.   "Aircraft" that appear to be ground vehicles ("fly" on roadways and at lower speeds) are filtered out.   Note that one or two non-aircraft mobile stations are also tracked as favors to individuals.

APRS stations not tracked here can most likely be found at one of the APRS Tracking Links on the sidebar at the left.   aprs.fi is highly recommended.

• For how long will position reports be available?


The goal is to retain position reports for one year but in order to maintain a reasonable database file size and performance, certain position reports will be deleted periodically.   Here are some conditions under which position reports are deleted before a full year:


• If a station's position has had no views within the current month, all of that station's position reports are deleted on the last day of the month regardless of their age.


• If a station with an aircraft symbol is found to be a ground station (or mixed ground and air), all of that station's position reports are deleted and new ones will not be displayed.


• If position reports arrive via UI-View32, DSTAR, or other direct injection into the APRS IS servers (i.e. non-RF methods), those position reports are deleted.


• If a station beacons excessively (too frequently), that station's position reports are deleted much sooner than after one year.

• How do I use Google Earth to "fly along" or play a tour of a track?


The Google Earth fly-along and tour require processing a small .KML file.   This has been problematic in Windows Vista and Windows-7 has not been tested.   The remainder of this discussion does not apply to computers using those operating systems.

Lets assume you're reading this because you'd like to try the Google Earth network link or track/tour functionality from the user interface page (items 7. or 8.) or the page that displays all tracks for a particular station.   Lets further assume that you have Google Earth installed on your PC and have at least a little bit of experience using it.

The Google Earth network link functionality is only useful if a station is presently in motion.  It displays a "birds-eye view" of what the pilot sees and is refreshed every 30 seconds.  If the aircraft has moved the station's icon "flys" to the new position and the map is refreshed.  No operator action is necessary to see a continually updating display. When the station stops moving, there are no further updates.

The Google Earth track/tour functionality displays a previously completed track or "replays" a track by "flying" a tour of it. It creates a collection of points in Google Earth's Places pane (under Temporary Places) that can be viewed or "toured".  Select Tools | Play Tour from the menu or use the controls below the Places pane to start, pause, or stop the tour.

Here are some tips for optimum use:


Do not check more than one network link or track simultaneously in the Places pane or Google Earth will attempt to fly back-and-forth between them.  This is probably not the effect you want.


You can save an interesting network link or track permanently under My Places and revisit it by checking it whenever you run Google Earth.  Again, check only one item at a time.


The default parameters are generally satisfactory for the Tour but they can be modified to taste by selecting Tools | Options | Touring tab from the menu.