[Xastir-dev] args to data_add()

[Owen DeLong]

I wasn't expecting it to display things in 3D (I don't think that's what's
wanted here, either), but, if it can keep track of altitude, that's 90%
of the battle.

Let me provide a little background on what I think is wanted here...

I think they want to use XASTIR to simulate (some of) the moving
map component(s) of a glass cockpit display.  This is usually
an instrument (flat panel display or CRT) which sits next to
or under the "primary flight display" and combines the output of
a number of different avionics (whichever are present in the
particular aircraft) with some abilities for the pilot to turn
on and off different capabilities...

	GPS/VOR/DME/ADF/LORAN/INS
	Map Database
	NavData Database
	TCAS
	RADAR
	WXDATA
	Flight Director
	VNAV

Some definitions for the aviation uninitiated:

	VOR	VHF Omnidirectional Range -- A radio navaid transmitting
		from a fixed location that allows the aircraft to determine
		it's direction from the VOR based on phase differentials
		in subcarriers on the transmitted signal.

	DME	Distance measuring equipment -- Slant range distance from
		a fixed location based on RTT for an interegator signal
		initiated by the aircraft.

	ADF	Automatic Direction Finder -- LF Direction Finder points
		sort of at a fixed transmitting station -- mostly obsolete.

	LORAN	Another type of area navigation, an earth-station based
		predecessor to GPS used primarily for maritime applications,
		but, found in some aircraft.

	INS	Inertial navigation system.

To XASTIR, all  of these could be mostly made to look like a GPS thing.

NavData database differs from a map database in that instead of containing
topographical features, it contains navaids, airports, waypoints, etc.
which are relevant to aviation for enroute and approach and departure
operations.

TCAS stands for Traffic Collision Avoidance System.  It is a device
required in all part 121 air carrier aircraft and most part 135 aircraft
over a certain size.  It displays a 2d picture of other aircraft in
proximity and categorizes them into green, yellow, or red depictions
based on how close they are (in 3D).  That is, an aircraft 3 miles
away at your same altitude is green.  An aircraft at your location
and 1000 feet above or below you is green.  An aircraft 500 feet
above or below you and 1 mile away is yellow.  An aircraft at your
altitude and <3 miles away is red, etc.  It also produces audible
alerts, and, in some cases has capabilities to instruct the autopilot
to avoid a collision hazard.

WXDATA is weather data (such as surface analysis, composite radar,
satellite images, etc.) which are uplinked to the cockpit and can
be overlayed on the moving map.

Flight Director is basically the combination of things that figure out
what to tell the autopilot.  Often, the FD can also be used in a display
only mode, where it doesn't command the autopilot, but, displays visual
cues to the pilot of what commands it would give to the autopilot.  In
fact, this is called "FD MODE" on many simpler autopilots in small aircraft.

VNAV is Vertical Navigation information from an ILS, GPS, or other source.

TCAS is the thing I was figuring XASTIR might have the most trouble 
providing
or accepting data for, but, if XASTIR already keeps track of altitude, then,
it's just a matter of creating a way to give it rules for proximity alerts
and enabling those proximity alerts.  I think a programmable proximity
alert capability would be a useful feature in XASTIR in general, and, not 
just
for this purpose.

Anyway, this is already much longer than I intended, so, I'll leave it
at that.  As usual, it's just my $0.02, but, nobody's told me to shut
up and go away yet, so, I've kept talking. :-)

Owen