[Xastir-Dev] Re: Xastir SAR feature added

[Curt Mills, WE7U]

On Fri, 19 Sep 2003, Owen DeLong wrote:

> What about a form that takes PLS, Vmin, Vmax, and TLS, Pdir, Cdir and
> then tracks the probability arcs expanding/contracting them appropriately
> with time.
>
> Example/Explanation:
>
> PLS	=	Point Last Seen
> Vmin	=	Minimum anticipated speed
> Vmax	=	Maximum anticipated speed
> TLS	=	Time Last Seen (to compute likely position now from PLS
> Pdir	=	Probable Direction of Travel
> Cdir	=	Confidence in Pdir (expressed as degrees).  Larger number
> 		wider arc.  180 = full circle (+/- 180 degrees from Pdir)
>
> This would allow you to input the above data about the subject, then, Xaster
> could maintain a "track" on the possible/probable position of the subject
> based on (Vmin+Vmax)/2 and draw a shaded search target area which would
> update in real time.  The search target area would be bounded by the
> Vmin arc, the Vmax arc, and straight lines between the corresponding edges
> of the two arcs.  A third arc (the "likely position" arc) would be drawn
> in the middle.  This way, the search area will grow (as it needs to) with
> time, and, also move with the likely direction of travel of the subject.
>
> The only real problem I see with this is that it would involve the
> assumption
> that whatever direction the subject was moving they kept moving in that
> direction.  It wouldn't allow, for example, for a subject wandering in
> circles.
>
> I think the behavior would be adequate for that with a 180 Cdir, but,
> it would need some testing and such.  I am not a SAR expert, but, this
> at least sounds like a good idea t me.

I'm no expert either, but am trying to learn fast.  I'm going to try
to take some of the multi-day courses regarding search management
theory over the next year or two.

The idea you listed above is similar to what I first wanted to do,
at least regarding the circle that continuously expands based on
time last seen and the current time/max anticipated speed.  I hadn't
thought about trying to do anything regarding probably direction of
travel, but I think that part might be problematic.

When I discussed my idea with people in-the-know, they didn't like
it.  What they wanted was fixed circles at 25% and 75% sizes based
on the probability that the subject might be in that area based on
collected statistics on lost people.

I've been looking into these stats and now have data for 10% through
100% circles for both U.S. and England/Northern Ireland.  There may
be data for Australia available soon as well.

I'll try to add this stuff in, but might have to have checkboxes for
which circles to display, as displaying 10 circles gets kind of
cluttered.

There are much more advanced search techniques as well.  This is
just the first step.  As I learn about them I'll try to add them to
Xastir.

-- 
Curt Mills, WE7U                    hacker_NO_SPAM_ at tc.fluke.com
Senior Methods Engineer/SysAdmin
"Lotto:    A tax on people who are bad at math!"
"Windows:  Microsoft's tax on computer illiterates!" -- WE7U
"The world DOES revolve around me:  I picked the coordinate system!"