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<title>SaVi satellite constellation visualization - user manual</title>
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<h1 align="center"><i>SaVi</i> - satellite constellation visualization</h1>
<h1 align="center">User manual</h1>
<h2>Contents</h2>
<ol>
<li><a href="#other">Other documentation for <i>SaVi</i></a></li>
<li><a href="#main">The main <em>SaVi</em> window</a></li>
<li><a href="#coverage">The coverage panel</a></li>
<li><a href="#fisheye">The fisheye window</a></li>
<li><a href="#hints">Further hints</a></li>
</ol>
<h2><a name="other">1. Other documentation for <i>SaVi</i></a></h2>
<p>
This manual introduces <i>SaVi</i> to the user. Descriptions of the satellite
constellations that <i>SaVi</i> simulates are provided from the <b>Help</b>
menu.
</p>
<p>
Other documentation is available for <i>SaVi</i> in textfiles supplied with the
<i>SaVi</i> software, which can also be read from the <b>Help</b> menu:
</p>
<ul>
<li><a href="../README">The <i>SaVi</i> README</a> introduces <i>SaVi</i> (and
<i><a href="http://www.geomview.org/">Geomview</a></i>, which <i>SaVi</i> uses for
three-dimensional rendering), compiling <i>SaVi</i> for your system, and launching
<i>SaVi</i>.</li>
<li><a href="../BUGS">Known bugs in <i>SaVi</i></a> are documented.</li>
<li><a href="../README-COVERAGE-TEXTUREMAP">Sending Earth coverage maps from
<i>SaVi</i>'s Coverage panel to <i>Geomview</i></a> is discussed separately.</li>
<li><a href="../COPYRIGHT">Copyright and software distribution and use permissions
for <i>SaVi</i></a> are also given.</li>
</ul>
<p>
<b>Further information on <em>SaVi</em> is available on the web at
<a href="http://savi.sourceforge.net/">http://savi.sourceforge.net/</a> and <a href="http://info.ee.surrey.ac.uk/Personal/L.Wood/software/SaVi/">http://info.ee.surrey.ac.uk/Personal/L.Wood/software/SaVi/</a>.</b>
</p>
<p>
Support for <em>SaVi</em> is provided via the
<a href="https://lists.sourceforge.net/lists/listinfo/savi-users">savi-users mailing list</a>.
</p>
<p>
<i><a href="http://www.geomview.org/">Geomview</a></i> provides <i>SaVi</i> with
three-dimensional rendering capabilities.
When using <i><a href="http://www.geomview.org/">Geomview</a></i>, the <i>Look</i>,
<i>Fly</i> and <i>Orbit</i> buttons
in its toolbar are the most useful; the stationary axes allow you to see the Earth
rotating against something fixed as you orbit your camera view around.
(<i>Rotate</i> leaves the cameras in all views fixed, while rotating all objects;
<i>Orbit</i> allows you to alter a single camera window.)
</p>
<p>
<a href="http://www.geomview.org/docs/"
>Documentation for <em>Geomview</em></a>, describing the many features of <i>Geomview</i>,
is available separately on the web at
<a href="http://www.geomview.org/">http://www.geomview.org/</a>.
</p>
<p>
Note that<i> SaVi</i> has a number of simple command-line options that can be seen by typing:<br>
<code>./savi -help</code><br>
which provides brief summary documentation of the available options.
<p>
<p>
Below is a brief guide to the main features of <i>SaVi</i>'s graphical user interface:
</p>
<h2><a name="main">2. The main <i>SaVi</i> window</a></h2>
<p>
The main window is where satellite parameters are edited and where <i>Geomview</i>
(if it is in use) is controlled from the <b>Rendering</b> menu. The simulation
is run forwards or backwards in time using the <b>>></b> and <b><<</b>
buttons on the playbar at the bottom of the window. <b>></b> and <b><</b>
step forwards or backwards a single interval of time; the time interval between
simulation steps is set to a default of sixty seconds, and can be changed here.
</p>
<p align="center">
<img src="images/savi-main.png" alt="SaVi's main window"><br>
<b>Main window - to see this, launch <i>SaVi</i>.</b>
</p>
<p>
Resizing this window to make it larger, so that you can see information
on more satellites at once, is a good idea.
</p>
<p>
Double-click a line listing satellite parameters to open the 'Edit satellite
parameters' window and edit values directly. Press return after entering each value
to update the satellite and change the simulation. A custom list of edited
satellites can be saved for posterity as a script to be loaded in again later -
see the <b>File</b> menu in the main window's menubar.</p>
</p>
<p>
Clicking a line listing satellite parameters highlights it, giving it a purple
cross in the Coverage and Fisheye windows, and a yellow surround in Geomview's
Camera window. Control-clicking a line adds it to or removes it from the current
selection. Shift-clicking a line includes the range of satellites from the
current selection to that line.
</p>
<p>
The menubar's <b>Edit</b> menu allows you to copy or cut selected satellites,
or edit existing or new satellite parameter lines, via an edit box. Like all
<i>SaVi</i> windows, this edit box can be left open while other windows are
active. The edit box will always show parameters for the last-selected
satellite.
</p>
<p align="center">
<img src="images/savi-edit.png" alt="SaVi's edit box"><br>
<b>Edit window - to see this, use the Edit menu, or double-click a satellite
parameter line.</b>
</p>
<p>
Individual satellites and their coverage can be hidden from view here, by using
the checkboxes.
</p>
<p>
Simulation constants can also be edited from the <b>Edit</b> menu. Altering these
from Earth normal is not for the faint of heart.
</p>
<p align="center">
<img src="images/savi-constants.png"><br>
<b>Simulation constants - to see this, use the Edit menu.</b>
</p>
<p>
The menubar's <b>Views</b> menu allows you to open the coverage panel and fisheye
windows, described further below. Opening the coverage panel is often the first
thing that you do upon launching <i>SaVi</i>.
Other options in the <b>Views</b> menu duplicate the
playbar at the bottom of the window, including the 'Restart' button to reset the
clock to time 0.
</p>
<p>
The <b>Constellations</b> menu allows you to load in simulations of known satellite
constellations, both existing and proposed. You can also empty space by deleting all
created satellites, or run the rosette generator to easily create a custom constellation.
The simulations on this menu are split into several groups:
</p>
<ul>
<li>simple theoretical constellations</li>
<li>systems in use</li>
<li>navigation constellations</li>
<li>non-geostationary equatorial rings</li>
<li>huge broadband proposals, mostly from the 1990s (best viewed using fast computers!)</li>
<li>other system proposals (not built)</li>
<li>sample TLE (two-line element) files. Although <i>SaVi</i> has very elementary TLE
parsing capabilities, simulation from TLEs is not at all accurate! This is still
experimental, and not recommended for use.</li>
</ul>
<p>
Decriptions of these systems are available in the Details window that is always
accessible from the <b>Help</b> menu. Many of these constellations are described in a <a href="http://info.ee.surrey.ac.uk/Personal/L.Wood/publications/talks.html#isu-summer-06">tutorial
introducing satellite constellations</a> given to the International Space University.
</p>
<p>
Note that loading in a constellation from the menu replaces all existing satellites.
To add a constellation to existing satellites that you wish to preserve, use Load... in
the File menu, and load in a Tcl script from <i>SaVi</i>'s <code>data/</code> directory.
</p>
<p>
Rosette constellations can be easily created using the Ballard rosette tool,
which can also generate a number of preset constellations.
</p>
<p align="center">
<img src="images/savi-rosette.png"><br>
<b>Ballard rosette tool - to see this, use the Constellations menu.</b>
</p>
To save an existing constellation you have created, such as one generated using the
Ballard rosette tool, use the <b>File</b> menu's <i>Save satellites as Tcl
script...</i> option. To begin from scratch, either delete all satellites, or
select Empty space, and confirm the dialog that comes up.
</p>
<p align="center">
<img src="images/savi-empty.png"><br>
<b>Empty space of all satellites dialog - to see this, use the Constellations menu.</b>
</p>
<p>
The <b>Rendering </b>menu includes a <i>Real-time mode</i> option that attempts
to synchronise <i>SaVi</i> to the computer's clock, so that an interval is
simulated every second. If you set to 1 second per interval, <i>SaVi</i> attempts
motion in real time. This mode option is most useful on very fast computers.
</p>
<p>
The <b>Rendering</b> menu is complete when <i>SaVi</i> is running with
<i>Geomview</i>. The full menu allows you to control how <i>Geomview</i> shows
the constellations in its Camera windows. To change the satellite type shown in
<i>Geomview</i>, select a marker type from the top section. To restore the
default green dots, select that marker type again.
</p>
<p>
By turning off <i>Show central body</i>, an outline Earth is produced. This is
useful when used with <i>Geomview</i>'s spherical projection (in the <i>Geomview</i>
window's <b>Space</b> menu.)</p>
<p>
<i>Animate in Geomview</i> can be turned off temporarily if <i>Geomview</i> becomes
problematic, so <i>SaVi</i> can be used standalone. This option is useful on
slower computers.
</p>
<p>
The Help menu identifies <i>SaVi</i> and provides brief installation information.
</p>
<h2><a name="coverage">3. The coverage panel</a></h2>
<p>
In the coverage panel a map projection of the Earth and visible coverage is
shown. The coverage panel is where most viewing work in <i>SaVi</i> is done.
It is likely that this will be the first option selected once <i>SaVi</i> is
running, and that most work will be done using the menubar at the top of this
panel's window.
</p>
<p>
When the coverage panel is first opened from the <b>Views</b> menu, you will
be asked how large you want the map to be, and you can also select how many
coverage diversity colours are needed.
The Earth map can be either 600x300 pixels or 1024x512 pixels in size. Four
colors is the default; more are useful when viewing large numbers of
satellites, such as the GPS and Galileo navigation constellations.
</p>
<p align="center">
<img src="images/savi-choose.png" alt="choose coverage parameters"></br>
<b>Choose coverage panel size/colours - to see, use Views menu on main window.</b>
</p>
<p>
After you have chosen, the coverage panel will open. Here, the smaller
coverage panel is shown.
<p align="center">
<img src="images/savi-coverage.png" alt="coverage panel"></br>
<b>Coverage panel - to see, use Views menu on main window.</b>
</p>
<p>
Stretching this window horizontally
will show two projections side-by-side; this is useful for looking at coverage
at the edge of the map, which lies in the middle of the two copies.
</p>
<p>
A number of different map projections can be chosen:
</p>
<ul>
<li>The default unprojected view is most useful for saving maps in to show
to others, and for sending texturemaps to <i>Geomview</i>. The texturemapping feature
is controlled from the coverage panel's <b>Rendering</b> menu.</li>
<li>The cylindrical map shows high latitudes and poles less clearly than the
unprojected view does. This map can also be sent to Geomview.</li>
<li>The sinusoidal views may be of use for examining coverage in the map centers.</li>
<li>The spherical views are a poor substitute for running <i>Geomview</i>,
to gain an idea of 'real' coverage on a globe.</li>
</ul>
<p>
Clicking in the map sets coordinates that are passed to the fisheye window,
and can then be selected in that window to replace the current coordinates in use.
This is a two-step process to prevent stray clicks from inadvertently changing
the fisheye. To change the fisheye in one step, control-click the coverage map.
</p>
<p>
Satellite coverage (which defaults to yellow/red) is intended to give an idea of
the number of satellites visible from a point, or <i>available diversity</i>.
The higher the number of satellites covering a point, the deeper the shade of red.
</p>
<p>Interval decay (which defaults to shades of blue) is intended to give an idea of
where a satellite footprint has been and is going, even when you look at a still map
snapshot. Turning this feature off replaces blue with white.
</p>
<p>
The sunlight checkbox shows a day/night terminator, reusing the last two interval decay
colors. Sunlight is simulated as a 'special' satellite zero, shown at the start of the
main satellite list when sunlight is turned on. Sunlight begins with time zero as an
equinox.
</p>
<p>
Map colors can be controlled to taste by the <b>Shading</b> menu or by clicking the
color wells in the key individually to launch a color selector. 'Change shading'
and 'Shade between end colors' will always produce ranges of tasteful hues. To alter
just the coverage or interval decay colors, uncheck the 'Show coverage' or 'Add
interval decay' checkboxes before using the shading menu options.
</p>
<p>
Satellites selected in the main window will be shown in the coverage panel as
purple, rather than green, as will their groundtracks.
</p>
<p>
Still map snapshots can be saved from the <b>File</b> menu. A simple <code>ppm</code>
bitmap format is used, and compressed with gzip. These files can be read directly
with <b>The Gimp</b> (GNU Image Manipulation Program, available from
<a href="http://www.gimp.org/">http://www.gimp.org/</a>).
</p>
<p>
The coverage of all satellites is controlled in the coverage panel by angle,
pop-up menu, and slider. The angle is between 0 and 90 degrees. The angle can either
indicate either:
<ul>
<li>the <em>mask elevation</em>. This is the minimum angle above the horizon and through
the atmosphere needed to establish communication with the satellite. This is measured from
the ground terminal.
<li>half the angle of the useful satellite beamwidth, referred to as the
<em>half-angle</em>. This is measured from the overhead satellite.
</ul>
<p>
The default mask elevation is generally more useful, as it can be shown for the ground
terminal in the fisheye view.
A mask elevation angle of zero degrees is the same as a half-angle of ninety degrees
when the satellite is directly over the ground terminal.
The slider to the right alters the angle value directly.
</p>
<p>
Computed coverage estimates are currently not accurate, and vary between projections.
</p>
<p>
The playbar is repeated at the bottom of this window for convenience.
</p>
<h2><a name="fisheye">4. The fisheye window</a></h2>
<p>
The fisheye window shows a view of the sky looking upwards from the ground, with the
horizon around the outside of the circle. North is to the top of the fisheye. The
default location is at zero point (zero longitude, zero latitude, zero altitude,
floating on the sea just off the coast of Africa).
</p>
<p align="center">
<img src="images/savi-fisheye.png"><br>
<b>Fisheye panel - to see, use Views menu on main window.</b>
</p>
<p>
The fisheye window is completely resizeable, and will scale the fisheye area to
suit. A larger fisheye shows a large number of satellites in view much more clearly.
</p>
<p>
If <i>ground terminal mask elevation</i> is selected from the coverage panel, the mask
circle will be shown, and the time a satellite spends in view (i.e. within the mask
area) will be indicated next to the satellite. Note that times are only accurate to
+/- half the simulation interval, assuming that a satellite began moving in the
fisheye outside the mask area. Setting a smaller simulation interval provides more
accurate time-in-view estimates.
</p>
<p>
<i>Enter new coordinates</i> updates the fisheye to use the values in the white
text boxes, which will be copied to the actual coordinates shown higher up in the fisheye panel.
Use this feature to determine how many satellites are visible from a selected point
on the Earth.
</p>
<p>
<i>Reverse fisheye view</i> switches East and West, to give an idea of satellites
moving over the Earth. This can be compared with <i>Geomview</i>'s spherical view
with the central body turned off, mentioned earlier.
</p>
<h2><a name="hints">5. Further hints</a></h2>
<p>
The best, most accurate, way to simulate a custom constellation in <i>SaVi</i> is
either to:
</p>
<ul>
<li>write a Tcl script, similar to the existing Tcl scripts in the <code>savi/data</code>
directory. Discussion of Tcl and the <code>SATELLITE</code> keywords specific to <i>SaVi</i> is
outside the scope of this note - but much can be learned from reading the code and
comments in existing scripts. Further information on Tcl is available from
<a href="http://www.tcl.tk/">http://www.tcl.tk/</a></li>
<li>improve the TLE-handling code in <code>savi/tcl/constellations.tcl</code> so that
it works more accurately, by staring at existing FORTRAN code and translating it into Tcl.
That is likely not for the faint of heart.</li>
</ul>
<p>
The background color in <i>Geomview</i> is set at the start of
<code>savi/oogl/savi.oogl</code>, as three fractional values between 0 and 1,
representing Red, Green and Blue.<br>
<b>0 0 0</b> is black.<br>
<b>1 1 1</b> is white.
</p>
<p>
<i>Geomview</i> can have multiple cameras open showing different
views. Scripting of camera actions in <i>Geomview</i> (using its oogl
object-oriented graphics language, which is a degenerate form of lisp) can be
very powerful.
</p>
<p>
Notes on sources and for and details of simulated constellations can be found in the
comments to each constellation script. See the <code>savi/data</code>
directory, or use the <b>View Source...</b> button at the bottom of the
<b>Help</b> menu window where details of each constellation are displayed.
</p>
<p>
<b>Use <i>SaVi</i> with <i>Geomview</i> 1.9 or later. This is strongly recommended.<br>
Use the latest <i>Geomview</i> release from <a href="http://www.geomview.org/">http://www.geomview.org/</a>.</b>
</p>
<p>
<b>Further information on <i>Geomview</i> is available on the web at
<a href="http://www.geomview.org/">http://www.geomview.org/</a></b>
</p>
<p>
<b>Further information on <i>SaVi</i> is available on the web at
<a href="http://savi.sourceforge.net/">http://savi.sf.net/</a></b>
</p>
<hr>
<small><a href="http://info.ee.surrey.ac.uk/Personal/L.Wood/">Lloyd Wood</a>
(<a href="mailto:lloydwood@users.sourceforge.net">lloydwood@users.sourceforge.net</a>)
</small>
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