.TH MARSV 1
.SH NAME
marsv \- View PDS images and measure the elevation of Mars surface using
MOLA grid data; Output the result to a postscript formatted file
.SH SYNOPSIS
.B marsv
.SH DESCRIPTION
.I Marsv
is a GUI program for measuring Mars elevation, latitude and longitude at the location
pointed at by the mouse cursor, on a Qube image or MOLA grid data.    The program
draws a contour map overlaid on the image using MOLA grid data, and generates a
postscript output file.
.PP
Marsv is intended to be an acme like user interface for manipulating Mars images
with additional menu barproperty for 3 button mouse.   The Left button shows
the category name of the item, the Middle button executes the indicated job
by the menu name, and the Right button lists the items for that category so that
the user can choose and execute one.
.PP
In Altitude menu of ISISmenu category of QUBELoad menu or MOLALoad menu,
the Left button shows the user the values of elevation, longitude and latitude of the
location that the mouse points to.
When the mouse in this mode is dragged, those values will be shown continuously,
which makes you to understand the real shape of the object you are now watching.
When you want to erase these data from the screen, press the Middle button.
.PP
In Contour menu of ISISmenu category of QUBELoad menu, dragging button 3 can
make correction for the minor discrepancy between that indicated by MOLA grid data
and by Qube image data.  After this recalibration, remapping of the countour will
be necessary to get a correct one.   The values of longitude and latitude
shown in Altitude menu of ISISmenu category are also recalculated by the above
procedure.  In short, you have to confirm the accuracy of those data shown by the mouse
over the contour maps, and if necessary, that recalibration should be done.
Those two values will not usually match each other from our experiences.
.PP
Marsv assumes there is a MOLA grid data (such as ieg0031t.img for 0.031 degree
grid) in the $home/data/mars/mola/ directory.   Additionally, marsv can read many
other PDS formatted images of other planet (and such as gif images of course), and
make simple annotations using Pen menu by changing colors from Palette menu.
.SH IMPLEMENTATION
Marsv designed as a single threaded concurrent program, ie. only a process can
include many threads, using thread(2) and control(2) libraries of Plan 9.   All the
controles to a window should be done by sending a control message to an appropriate
channel, which may not be necessarily attached to a visible window.   Four general
purpose user interfaces with its own windows are implemented as shown in struct
Form, struct Filebrowse, struct Select and struct Viewer.   Those structures are
constructed using two new basic structures, named struct Win and struct WinComm,
which control their shape, position and behaviour.   All those strructures have ctl,
data, winctl and event channels to send or receive the control messages or data,
the last of which is just a handle to a real channel.    Those channels will be created
by the function of mkwincomm() in wincomm.c.
.PP
Struct Canvas is prepared to provide layer structures to marsv image by using
memdraw and layer functions in memdraw(2) libraries of Plan 9, which is a
mechanism to make multiple layers in the user's memory space.   Each layer may
be for drawing the altitude, latitude and longitude data at the moving mouse point,
or for drawing image data themselves.   Struct Layer and CanvasBase are used as
their base structures.   The other many structures from control(2) library are also
used through newly defined structure of Wincontrol.  Struct Canvas related thread
has no winctl channel, then, has no distinct visible window, where channels are
created individually, and mkwincomm() is not applied.   The struct Viewer is used
to copy the layered image to visible image.
.PP
We added struct Textbutton3 for our usage of 3 button menu bar to
control(2) library.  You may want to copy textbutton3.c.lib file to /sys/src/libcontrol/txtbutton3.c,
and do mk the control library with some change to /sys/include/control.h and
/sys/src/libcontrol/control.c and mkfile to make those usable.
.PP
If you want to extend functionarities to marsv, please refer to files such as imager.c
or marsv.c.
.SH BUGS
Some images with larger width may fail to be shown, because of the limit
of 9p protocol.  16 bit color is not supported to save the created image.  You will
lose true color from saving in 16 bit true color mode of Plan 9.
To input file name etc. onto the entry box, you have to hit Enter key at the end
to ensure the input, which is not a bug though.   There may be many other bugs.
.SH AUTHORS
Marsv was written by Yoshitatsu Suzuki and Kenji Okamoto of Osaka Prefecture
University.   We are financially supported by the citizens of Osaka Prefecure Japan.