1 XEARTH Displays a shaded image of the Earth in the root window SYNOPSIS $ xearth [-latitude lat][-pos lat lon][-noshade ][-sunpos lat lon] [-size w h][-label ] [-wait secs][-day pct][-night pct][-nofork ] [-nogeostatic lat lon][-version ][-ppm ][-gif ][-display dpyname] 2 DESCRIPTION Xearth sets the X root window an image of the Earth, as seen from your favorite vantage point in space, correctly shaded for the current position of the Sun. By default, xearth forks a child process that runs in the background, updating the displayed image every five minutes to reflect changes in the Sun's position. This behavior can be changed with the -wait and -nofork options (see below). Xearth can also render directly into PPM and GIF files instead of drawing in the root window; see the -ppm and -gif options below. 2 OPTIONS -latitude The latitude of the XEARTH program :) Default 0 . -pos lat lon Specify the point on the Earth's surface (latitude and longitude, specified in decimal degrees) around which the displayed image should be centered. If not specified, this position defaults to 0 degrees latitude, 0 degrees longitude. -noshade Disable shading, use flat colors to render land and water. -sunpos lat lon Specify the point on the Earth's surface (latitude and longitude, specified in decimal degrees) where the Sun is directly overhead. By default, xearth calculates and updates this position according to the current time. -size w h Specify an image w pixels wide and h pixels high. When rendering into the X root window, these values default to the dimensions of the root window. When producing a PPM or GIF file instead of drawing in the X root window (see the -ppm and -gif options, below), both values default to 512. -label If rendering into the X root window, also provide a label in the lower right-hand corner that indicates the viewing position and current position of the sun. -wait secs Wait secs seconds between updates of the root window. This value defaults to 300 seconds (five minutes). -day pct Specify the brightness that should be used to shade the day side of the Earth. Pct should be an integer between 0 and 100, inclusive, where 0 indicates total darkness and 100 indicates total illumination. This value defaults to 100. -night pct Specify the brightness that should be used to shade the night side of the Earth (see description of pct immediately above). This value defaults to 25. -nofork If rendering into the X root window, don't "auto-background" by forking off a child process. -nogeostatic lat lon By default xearth keeps a geostatic point of view of the earth. By specifying this option, the sun stays static, and the earth rotates. the latitude and longtitude values specified, are simple offests to the viewing point. A value of zero on both, keeps the position of the sun, in the middle of the picture. -version Print what version of xearth this is. -ppm Instead of drawing in the X root window, write a PPM file (24-bit color) to standard out. -gif Instead of drawing in the X root window, write a GIF file (8-bit color) to standard out. 2 NOTES This man page documents xearth version 0.5. There are a number of very useful improvements that I'd like to make (such as support for other than eight-bit pseudocolor visuals, better error recovery, getting options via X resources, etc.), but I really should be working on my thesis instead of hacking on this. The map information used in xearth was derived from the "CIA World Data Bank II map database," as taken from some "cbd" files that were apparently originally generated by Brian Reid at DECWRL. The Graphics Interchange Format(c) is the Copyright property of CompuServe Incorporated. GIF(sm) is a Service Mark property of CompuServe Incorporated. Kudos to Jef Poskanzer for his excellent PBMPLUS toolkit. 2 AUTHOR Copyright (C) 1989, 1990, 1993 by Kirk Lauritz Johnson. Modified 1993 by Dimitris Evmorfopoulos. Permission to use, copy, modify, distribute, and sell this software and its documentation for any purpose is hereby granted without fee, provided that the above copyright notice appear in all copies and that both that copyright notice and this permission notice appear in supporting documentation. The author makes no representations about the suitability of this software for any purpose. It is provided "as is" without express or implied warranty. 2 VMS_PORT Patrick Moreau, CENA/Athis-Mons, FRANCE (pmoreau@cena.dgac.fr)