[Xastir] Line of sight

[Rob Campbell]

Curt, WE7U wrote:
> 
> Like I said, it could be done.  Xastir is generic C-code.  Trickiest
> part would probably be adding the widget controls for the user
> interface.  If you would like to do the back-end code for this
> function, making sure to generalize it so that one could find out
> which stations were heard by any particular station, I'd volunteer
> to make the user interface tie-in for it.
> 
> First problem I can think of is that I'd like to see all positions
> that a digipeater could see directly, and Xastir doesn't keep the
> path information for previous positions.  For your application of
> non-moving stations it's not a big issue.  For moving stations it
> is.
> 
> Look at src/database.h.  In there are the structure definitions for
> the info kept for each station.  We keep the data in a
> multiply-linked-list structure, where we can get to it by time
> (either order) or by alpha-sorted-order, and we have an additional
> hash that lets us shortcut the linked list too.  Just figure out the
> data struct itself, navigating through all the stations is easy.
> 
> --
> Curt, WE7U.   APRS Client Comparisons: http://www.eskimo.com/~archer
> "Lotto:    A tax on people who are bad at math." -- unknown
> "Windows:  Microsoft's tax on computer illiterates." -- WE7U
> "The world DOES revolve around me:  I picked the coordinate system!"
> 

I'll take a look at the code when I have some time.  It's almost 5pm so 
I'll be heading home in a few minutes.  Do you think it would be better 
to store the old positions in another linked list, or an external 
database?  I would think that an external database would be needed, 
since the number of positions can grow to be very large.

Rob Campbell
KG6HUM