"earthtrack" uses "xplanet" to produce an orthographic image of the
earth upon which satellite names are placed over their respective
sub-satellite points. The globe can be centered either over your
groundstation location (default), or over the location any satellite
being tracked by PREDICT. The second method allows you to "fly with
the satellite" as it circles the globe. The map is updated every 20
seconds. By default, "earthtrack" connects to the PREDICT server
running on "localhost". These defaults may be overridden through
several command-line switches.
The -h switch allows a different PREDICT server name to be specified.
The -x switch option allows additional command-line parameters to be
passed to xplanet through earthtrack. (Note that
the argument that follows the -x switch must be enclosed in "quotes".)
The -u switch allows a different map update interval to be specified,
and the -c switch allows the map to be centered on a specific satellite.
For example:
earthtrack -c ISS -u 15 -h predictserver.org
allows earthtrack to invoke "xearth" as a display, centering the map
on the location of satellite "ISS", using host "predictserver.org"
as the host running PREDICT in server mode. The satellite name
specified must be the same as PREDICT displays in Multi-Tracking
mode. If a space appears in the name, then the entire name must
be enclosed in double quotes.
"xplanet" uses highly detailed photo-realistic maps of the world
available from a variety of sources to produce spectacular views
of the earth.
For example, if an uppercase -C is used rather than a lowercase
-c for the map center switch, such as in the following example:
earthtrack -C ISS
the map is not only centered on the location of the ISS, but the
map is also zoomed into an area slightly larger than the footprint
of the satellite. A range circle is also drawn on the map to
indicate the actual footprint of the spacecraft at the current
time.
If a map centered on the groundstation location is desired, then
footprint range circles for neighboring satellites are drawn on the
map. Range circles are drawn for satellites between 5 minutes prior
to AOS through the point of LOS. Such a display may be created simply
by executing "earthtrack" without any switches:
earthtrack
or with the -h switch to identify the remote host running PREDICT in
server mode:
earthtrack -h predictserver.org
If the satellite being tracked is in sunlight, then the satellite
name and range circle are displayed in white. If the satellite
is in darkness, then the color blue is used. If the satellite
is optically visible to the groundstation, then yellow is used.
"earthtrack" may also be used to generate graphics files for
use in web server environments. For example:
earthtrack2 -c ISS -x "-geometry 800x600 -output graphic.png"
will invoke "xplanet" to produce an 800x600 PNG image of the world
centered on the sub-satellite point of the ISS with a name of
"graphic.png". This feature, along with capabilities demonstrated
in the ~/predict/clients/samples directory, can be used to develop
satellite tracking and orbital prediction content for a web server.
"earthtrack" exits when its connection to
the PREDICT server is broken, such as would occur if PREDICT
is terminated while "earthtrack" is still running. The
application may be run as background processes by placing
an ampersand (&) at the end of the command line.
This version includes a -o switch to send the output to
the file /tmp/xplanet.png instead of to the screen.
For more creative uses of PREDICT and earthtrack, see John
Heaton, G1YYH's PREDICT and earthtrack modification web page
at:
http://voyager.mcc.ac.uk/Predict/
Happy Tracking!
73, de John, KD2BD
June 2003
OPTIONS
-c <satellite> (center on satellite)
-C <satellite> (center on satellite and zoom in)
-h <hostname running predict in server mode>
-o <output to image file>
-p <projection>
-x <command line arguments to pass along to xplanet>
-u <screen update interval in seconds>
AUTHOR
This man page was written by A. Maitland Bottoms, AA4HS, for Debian GNU/Linux.
