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xplanet

NAME

xplanet - render an image of a planet into an X window or file

SYNOPSIS

xplanet [options]

DESCRIPTION

Xplanet is similar to Xearth, where an image of the earth is rendered into an X window. All of the major planets and most satellites can be drawn. A number of different map projections are also supported, including azimuthal, Mercator, Mollweide, orthographic, and rectangular. The latest version can always be found at http://xplanet.sourceforge.net.

OPTIONS

Options need only be specified with enough characters to be unambiguous. Valid options to Xplanet are:

-arc_file

Specify an arc file to be plotted against the background stars. Each line in the file must have the following syntax:

 
 dec1 ra1 dec2 ra2
 
 

where declination is in degrees and right ascension is in hours. This option has no effect if -projection is specified.

-arc_spacing spacing

When drawing an arc, draw line segments that are spacing degrees apart. The default is 0.1 degrees. Line segments shorter than spacing will not be drawn.

-arc_thickness thickness

Specify the thickness of arcs. The default is 1 pixel. When drawing arcs on a planet using the arc_file option in the configuration file, use the arc_thickness option there too.

-background background_file

Use background_file as the background image, with the planet to be superimposed upon it. A color may also be supplied (e.g. -background "navy blue" or -background 0xff00ff).

-base_magnitude magnitude

A star of the specified magnitude will have a pixel brightness of 1. The default value is 10. Stars will be drawn more brightly if this number is larger.

-body body

Render an image of the specified planet or satellite. Valid values for body are sun, mercury, venus, earth, moon, mars, phobos, deimos, jupiter, io, europa, ganymede, callisto, saturn, mimas, enceladus, tethys, dione, rhea, titan, hyperion, iapetus, phoebe, uranus, miranda, ariel, umbriel, titania, oberon, neptune, triton, nereid, pluto, charon, random, and major.

The field of view can also be centered on a satellite location using "naif" or "norad", along with the satellite id. For example, "-body naif-82" will center the field of view on NAIF ID -82, which is the Cassini orbiter. Xplanet must be compiled with SPICE support and the required kernels must be present. See the README in the spice subdirectory for more details. Using "-body norad20580" will center the field of view on NORAD ID 20580, which is the Hubble Space Telescope. The appropriate TLE files must be present in this case. See the README in the satellites subdirectory for more information.

Using "path" will center the field of view on the direction of motion of the origin. This direction is relative to the direction of motion of the body specified by -path_relative_to.

Earth is the default body. This option is the same as -target.

-center +x+y

Place the center of the rendered body at pixel coordinates (x, y). The upper left corner of the screen is at (0,0). Either x or y may be negative. The default value is the center of the screen.

-color color

Set the color for the label. The default is "red". Any color in the rgb.txt file may be used. Colors may also be specified by RGB hex values; for example -color 0xff and -color blue mean the same thing, as do -color 0xff0000 and -color red.

-config config_file

Use the configuration file config_file. The format of config_file is described in README.config. See the description of -searchdir to see where xplanet looks in order to find the configuration file.

-date YYYYMMDD.HHMMSS

Use the date specified instead of the current local time. The date is assumed to be GMT.

-date_format string

Specify the format for the date/time label. This format string is passed to strftime(3). The default is "%c %Z", which shows the date, time, and time zone in the locale's appropriate date and time representation.

-dynamic_origin file

Specify an observer location. The location is relative to the body specified with -origin (by default, this is the Sun). The last line of the file must be of the form

 
 YYYYMMDD.HHMMSS range lat lon localtime
 
 

For example,

 
 19951207.120000     10.328   -3.018   97.709    9.595
 
 

The specified time is ignored and the current time is used. The range is in planetary radii, and lat and lon are in degrees. Localtime (in hours) is optional, but if present, it will be used in place of the longitude. Only the last line of the file is used. This file may be updated between renderings using a script executed with the -prev_command or -post_command options.

-ephemeris_file filename

Specify a JPL digital ephemeris file (DE200, DE405, or DE406) to use for computing planetary positions. Xplanet uses Bill Gray's code (http://www.projectpluto.com/jpl_eph.htm), which reads both big and little endian binary files. The ephemeris files found at ftp://ssd.jpl.nasa.gov/pub/eph/export/unix are big endian files, but you do not need to do any additional byte-swapping to use them. See the description of -searchdir to see where xplanet looks in order to find the ephemeris file.

-font fontname

Set the font for the label. Only TrueType fonts are supported. If the -pango option is used, fontname is taken to be the font family name (e.g. "Arial").

-fontsize size

Specify the point size. The default is 12.

-fork

Detach from the controlling terminal. This is useful on MS Windows to run xplanet from a batch file without having to keep a DOS window open. Be careful when using this option; it's easy to have multiple processes running at the same time without knowing it - check the Task Manager. On unix systems this is pretty much the same as running xplanet in the background.

-fov

Specify the field of view, in degrees. This option and the -radius option are mutually exclusive. This option has no effect if the -projection option is used.

-geometry string

Specify the image geometry using the standard X window geometry syntax, [<width>{xX}<height>][{+-}<xoffset>{+-}<yoffset>] (e.g. 256x256-10+10 puts a window 256x256 pixels in size 10 pixels away from the right side and 10 pixels below the top of the root window). The root window outside of the image will be black. This option may be used with -window or -output.

-glare radius

Draw a glare around the sun with with a radius of the specified value larger than the sun. The default value is 28.

-gmtlabel

Same as the -label option, but show GMT instead of local time.

-grs_longitude lon

The longitude of Jupiter's Great Red Spot (GRS). A typical value is 94 degrees. If this option is specified, longitudes on Jupiter will be calculated in System II coordinates. By default, longitudes are calculated in System III coordinates. When using this option, use an image map for Jupiter where the center of the GRS is at the pixel 0 column, or the left side of the image.

-hibernate seconds

After the screen has been idle for the specified number of seconds, xplanet will sleep. This option requires xplanet to have been compiled with the X Screensaver extension.

-idlewait seconds

Don't run Xplanet unless the screen has been idle for the specified number of seconds. This option requires xplanet to have been compiled with the X Screensaver extension.

-interpolate_origin_file

This option is only useful in conjunction with -origin_file. It computes the observer position at the current time by interpolating between values specified in the origin file. This is useful if you have spacecraft positions tabulated in an origin file, but want a real time view.

-jdate Julian date

Use the specified Julian date instead of the current local time.

-label

Display a label in the upper right corner.

-labelpos

Specify the location of the label using the standard X window geometry syntax. The default position is "-15+15", or 15 pixels to the left and below the top right corner of the display. This option implies -label.

-label_body body

Use the specified body to calculate the sub-observer, sub-solar, and illumination values in the label. This is useful with the -separation option.

-label_string

Specify the text of the first line of the label. By default, it says something like "Looking at Earth". Any instances of %t will be replaced by the target name, and any instances of %o will be replaced by the origin name.

-latitude latitude

Render the target body as seen from above the specified latitude (in degrees). The default value is 0.

-light_time

Account for the time it takes for light to travel from the target body to the observer. The default is to ignore the effects of light time.

-log_magstep step

Increase the brightness of a star by 10^step for each integer decrease in magnitude. The default value is 0.4. This means that a star of magnitude 2 is 10^0.4 (about 2.5) times brighter than a star of magnitude 3. A larger number makes stars brighter.

-longitude longitude

Place the observer above the specified longitude (in degrees). Longitude is positive going east, negative going west (for the earth and moon), so for example Los Angeles is at -118 or 242. The default value is 0.

-make_cloud_maps

If there is an entry in the config file for cloud_map, xplanet will output a day and night image with clouds overlaid and then exit. The images will be created in the directory specified by -tmpdir, or in the current directory if -tmpdir is not used. The names of the output images default to day_clouds.jpg and night_clouds.jpg, but may be changed by the -output option. If "-output filename.extension" is specified, the output images will be named "day_filename.extension" and "night_filename.extension". The dimensions of the output images are the same as the day image.

-marker_file

Specify a file containing user defined marker data to display against the background stars. The format of each line is generally declination, right ascension, string, as in the example below:

 
 -16.7161 6.7525 "Sirius"
 
 

For additional options which may be specified, see the marker_file entry in README.config. This option has no effect if -projection is specified. This option is not meant for city markers; for that use the marker_file option in the configuration file.

-markerbounds filename

Write coordinates of the bounding box for each marker to filename. This might be useful if you're using xplanet to make imagemaps for web pages. Each line looks like:

 
 204,312 277,324 Los Angeles
 
 

where the coordinates are for the upper left and lower right corners of the box. This file gets rewritten every time xplanet renders its image.

-north north_type

This option rotates the image so that the top points to north_type. Valid values for north_type are:

 
 body:        body's north pole
 galactic:    galactic north pole
 orbit:       body's orbital north pole (perpendicular to the orbit plane)
 path:        origin's velocity vector  (also see -path_relative_to option)
 separation:  perpendicular to the line of sight and the
              target-separation target line (see -separation option)
 
 

The default value is "body".

-num_times num_times

Run num_times before exiting. The default is to run indefinitely.

-origin body

Place the observer at the center of the specified body. Valid values are the same as for -target. In addition, "above", "below", or "system" may be specified. Using "above" or "below" centers the view on the body's primary and the field of view is large enough to show the body's orbit. Using "system" places the observer at the center of a random body in the same system as the target body. Two bodies are in the same system if one of the following is true:

 
  1) target and origin have same primary
  2) target is origin's primary
  3) origin is target's primary
 
 

If the body name is preceded by a dash, the observer is placed on the opposite side of the target from the specified body at a distance equal to the distance between the target and body. For example, -target earth -origin sun places the observer at the center of the sun. If -target earth -origin -sun is used, the observer is placed on a line connecting the centers of the earth and sun at a distance of 1 AU farther from the sun than the earth.

-origin_file origin_file

Specify a list of observer positions in origin_file. The positions are relative to the body specified with -origin (by default, this is the Sun). Each line should be of the form

 
 YYYYMMDD.HHMMSS range lat lon localtime
 
 

For example,

 
 19951207.120000     10.328   -3.018   97.709    9.595
 
 

Range is in planetary radii, and lat and lon are in degrees. The date is the only required value. If the localtime (in hours) is supplied, it will be used in place of the longitude. For each line in the origin file, the observer is placed at the specified position, relative to the body specified with -origin. This option is useful for showing spacecraft flybys or orbiting around a planet. Any line with a # in the first column is ignored.

-output filename

Output to a file instead of rendering to a window. The file format is taken from the extension. Currently .gif, .jpg, .ppm, .png, and .tiff images can be created, if xplanet has been compiled with the appropriate libraries. The image size defaults to 512 by 512 pixels but this may be changed by the -geometry flag. If used with the -num_times option, each output file will be numbered sequentially.

-output_start_index index

Start numbering output files at index. The default is 0.

-pango

Use the Pango (http://www.pango.org) library for rendering internationalized text. Pango uses Unicode for all of its encoding, and will eventually support output in all the worlds major languages. If xplanet has not been compiled with this library this option will be ignored. There appear to be memory leaks in the pango library, so I don't recommend letting xplanet run indefinitely with this option.

-path_relative_to body

Only used with -north path or -target path. The origin's velocity vector is calculated relative to the specified body. By default, this is the Sun.

-post_command command

-prev_command command

Run command either before or after each time xplanet renders an image. On MS Windows, you may need to use unix-style paths. For example:

 
 xplanet.exe -prev_command ./prev.bat
 
 

-print_ephemeris

Print the heliocentric rectangular equatorial coordinates (J2000) for each body xplanet knows about, and then exit.

-projection projection_type

The projection type may be one of ancient, azimuthal, bonne, equal_area, gnomonic, hemisphere, lambert, mercator, mollweide, orthographic, peters, polyconic, rectangular, or tsc. The default is no projection. Multiple bodies will not be shown if this option is specified, although shadows will still be drawn.

-proj_param value

Pass additional parameters for some projections. The only projections that use this option at present are the Bonne, Gnomonic, and Mercator projections. The Bonne projection is conformal at the specified latitude. Higher values lead to a thinner heart shape. The default is 50 degrees. The Gnomonic and Mercator projections use the specified latitude as the boundaries of the projection. The defaults are 45 and 80 degrees, respectively. This option may be used more than once for future projections that require additional parameters. Only the first value is used at present.

-quality quality

This option is only used when creating JPEG images. The quality can range from 0 to 100. The default value is 80.

-radius radius

Specify the radius of the globe as a percent of the screen height. The default value is 45% of the screen height. When drawing Saturn, the radius value applies to the radius of the outer ring.

-random

Place the observer above a random latitude and longitude.

-range range

Render the globe as seen from a distance of range from the planet's center, in units of the planetary radius. The default value is 1000. Note that if you use very close ranges the field of view of the screen can be greater than 180 degrees! If you want an "up close" image use the -radius option.

-rotate angle

Rotate the globe by angle degrees counterclockwise so that north (as defined by the -north argument) isn't at the top. The default value is 0. My friends in the Southern Hemisphere can use -rotate 180 to make the earth look like it should! For non-orthographic projections, the globe is rotated and then projected, if that helps you visualize what to expect.

-save_desktop_file

On Microsoft Windows and Mac OS X, xplanet creates an intermediate image file which is used to set the desktop. This file will be created in the -tmpdir directory. By default, this image is removed after the desktop has been set. Specifying this option will leave the file in place.

-searchdir directory

Any files used by xplanet should be placed in one of the following directories depending on its type: "arcs", "config", "ephemeris", "fonts", "images", "markers", "origin", "satellites", or "stars". By default, xplanet will look for a file in the following order:

 
 The current directory
 searchdir
 subdirectories of searchdir
 subdirectories of xplanet (if it exists in the current directory)
 subdirectories of ${HOME}/.xplanet on X11
 subdirectories of ${HOME}/Library/Xplanet on Mac OS X
 subdirectories of DATADIR/xplanet
 
 

DATADIR is set at compile time and defaults to /usr/local/share.

-separation body:dist

Place the observer at a location where the target body and the separation body are dist degrees apart. For example "-target earth -separation moon:-3" means place the observer at a location where the moon appears 3 degrees to the left of the earth.

-spice_ephemeris index

Use SPICE kernels to compute the position of the named body. The index is the naif ID code (e.g. 599 for Jupiter). The -spice_file option must be used to supply the names of the kernel files. This option may be used more than once for different bodies.

-spice_file spice_file

Specify a file containing a list of objects to display. A file containing a list of SPICE kernels to read named spice_file.krn must exist along with spice_file. See the README in the "spice" subdirectory for more information.

-starfreq frequency

Fraction of background pixels that will be colored white. The default value is 0.001. This option is only meaningful with the azimuthal, mollweide, orthographic, and peters projections.

-starmap starmap

Use starmap to draw the background stars. This file should be a text file where each line has the following format:

 
 Declination, Right Ascension, Magnitude
 
 

where Declination is in decimal degrees and Right Ascension is in decimal hours. For example, the entry for Sirius is

 
 -16.7161  6.7525 -1.46
 
 

See the description of -searchdir to see where xplanet looks in order to find the star map.

-target target

Same as -body.

-tt

Use terrestrial time instead of universal time. The two differ slightly due to the non-uniform rotation of the earth. The default is to use universal time.

-timewarp

As in xearth, scale the apparent rate at which time progresses by factor. The default is 1.

-tmpdir tmpdir

Specify a directory that xplanet will use to place images created using -make_cloud_maps. On Microsoft Windows, xplanet will write a bitmap file called xplanet.bmp to the specified directory. The default is the result of the GetWindowsDirectory call (C:WINDOWS on Win95). On Mac OS X, xplanet will create an intermediate PNG file in order to set the background. The default value is /tmp. On Windows and Mac OS X, the intermediate file will be removed unless the -save_desktop_file option is specified.

-transparency

Update the background pixmap for transparent Eterms and aterms. This option only works under X11.

-transpng filename

Same as the -output option, except set the background to be transparent when writing a PNG file.

-utclabel

Same as -gmtlabel.

-verbosity level

 
 level      output
 < 0        only fatal error messages
 0          non-fatal warning messages
 1          basic information        
 2          basic diagnostics        
 3          more detailed diagnostics
 4          very detailed diagnostics
 
 

The default value is 0.

-version

Display current version information, along with a list of compile-time options that xplanet supports.

-vroot

Render the image to the virtual root window. Some window managers use one big window that sits over the real root window as their background window. Xscreensaver uses a virtual root window to cover the screen as well.

-wait wait

Update every wait seconds.

-window

Render the image to its own X window. The size defaults to 512 by 512 pixels but this may be set by the -geometry flag.

-window_title title

Set the window's title to title. This option implies -window.

-xscreensaver

Same as -vroot.