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I'm not proposing a pseudolite.... or anything that resembles a GPS
signal at 1.5ghz. I say fake GPS, but i'm only meaning fake gps serial
data stream.<br>
<br>
I'd don't want your GPS to really work indoors... I want tiny track to
"think" your GPS is working by fiddling with the serial data coming
from the GPS. The IR beacon I mentioned will just transmit
$GPRMC<cr><cr>$GPRMC<cr><cr> over and over so
that your tiny trak will hear (see?) it as you enter a room. Once in
the room, you will not see it again until you exit - but your tiny trak
did "see" it as you entered the room - and it will remember that
position. At 4800 baud, we can send a 68character GPRMC sentance 7
times a second. Let's say you exit a room and there are two of these IR
beacons on either side of the door header aimed downward at 45 degrees.
Chances are your tiny track will "see" at least one GPRMC sentance as
you walk thru the doorway. As you proceed down the hallway into the
room, you'll see the IR beacon on the hallway side of the next door.
Your tiny trak will record this position as valid. If tiny trak thinks
it's time (ie it has been 3 minutes since the last transmit), it will
transmit a packet using the just heard location. Now, as you enter the
next room, as you pass under the doorway, your tracker sees the beacon
inside that room and records it's position to transmit at a later time.<br>
<br>
I'm proposing that you "hear" the position of the "room" as you enter
and use that posit when you want to transmit on 144.39 at some later
time. A simple circuit will allow the IR data to be inserted on the
same serial line as the GPS data and override GPS serial data if IR is
present. Of course, when you do go outside, and your GPS gets a fix,
you'll begin to accept data from it and <span
class="moz-txt-underscore"><span class="moz-txt-tag">_</span>that<span
class="moz-txt-tag">_</span></span> position data will be transmitted
on 144.39. I'm exploiting a feature in the tiny track where it
remembers it's last <span class="moz-txt-underscore"><span
class="moz-txt-tag">_</span>valid<span class="moz-txt-tag">_</span></span>
position and conitunes to transmit that position even when invalid data
is streaming in from the GPS the whole time. <br>
<br>
I know I'm probably rambling.... what would be slick would be to
program a bit of randomness into the IR beacons so that they
transmitted a series of different positions in a raduis around them -
think position ambiguity. Two different people walking thru the doorway
at slightly different times would record different positions and
therefore would not appear to be on top of one another on a map. Of
course you'd have to define the "random" area range when you program
the beacon. Perhaps just make it scan east to west, the "move" north
.001 of a minute and scan east to west again. Reset at the top corner
and start over again at the bottom corner.<br>
<br>
And finally, the point to indoor tracking is to know where people are
in a building... Say, for example at your EOC. Is Joe-Bob in the
building or is he out back smoking? Is he in the director's office or
the radio room? Which hall are you in at dayton? Especially on
multifloor buildings, it can take a while to round someone up. Or in a
hospital.... are you in the emergency triage, or in the L&D ward 3
flights up and at the other end of the building? Or in a school
dispatching the police "resource" officer (who shouldn't be at the
school anyway, but that is more or a decline of society issue). And
let's not forget we can also put a tracker on a piece of equipment
too. <br>
<br>
I think it would be slick to be able to ride all over the countryside
with my tracker, and when I got to the EOC, be able to continue to be
tracked all the way into the building. The means don't matter... if my
gps quits working indoors, I have come up with a way which I think will
supply my tiny trak with some position data, or Bob's idea of RFID
could superceed my invalid GPS positions from my tiny track (if we were
to implement RFID instead of the fake-gps signal). What kinda got all
of this started for me was seeing Tony Barrett at Dayton slip a pocket
tracker in his breast pocket and used a wrist mounted GPS from
garmin. Because the pocket track is so small, I was trying to think of
a way to feed it a location when indoors. If you already have a
pockettrak or d7, add $5 worth of parts to it, and for $5 a room you
can feed it position reports. ($5 a room assumes a $.25 LED, $.30 555
timer chip, and a $3 pic processor to complete the IR Beacon.)<br>
<br>
By the way, in a multi story building, I'd program the actual positon
of each room in lat/lon, but I'd falsify the altitude... 1 foot would
represent the ground floor... 2 feet would represent the 2nd floor and
so on. If your favorite aprs client showed altitude along with the
icon, you'd easily see what floor the person was on. The possibility
also exists that we could falsify the lat/lon to some unused part of
the county, or heck the middle of the atlantic ocean and place a map of
each floor of the building all end to end in the middle of "nowhere".
Of course people w/o a map of this spot in the ocean would have no idea
what the heck was going on out there! Also, we could also create GEO
files to feed to findu.com, and have findu display all the icons on top
of a GEO file that was not a map at all, but a blueprint of the
building! <br>
<br>
Wes<br>
<br>
Chris Kantarjiev wrote:
<blockquote cite="mid200506022056.j52KuKOA025981@moose.dimebank.com"
type="cite">
<pre wrap="">
</pre>
<blockquote type="cite">
<pre wrap="">Create a fake GPS satellite to be mounted above each doorway that
streams out the GPS coordinates of the room you are in.
</pre>
</blockquote>
<pre wrap=""><!---->
I'm afraid I don't understand this at all. The bitstream that comes
from the satellite constellation is completely different than the
GPRMC sentences that come out of the serial port...
</pre>
<pre wrap="">
This sounds incredibly neat. If we're already talking about installing
new receive hardware, I think it would be great to do this kind
of solution on 144.39 MHz.
I bet it's incredibly difficult to do well, though.
</pre>
<blockquote type="cite">
<pre wrap=""> What's the goal here?
</pre>
</blockquote>
<pre wrap=""><!---->
I'll echo this sentiment. And ask, in addition - other than the intended
audience, what does an RFID-based solution have to do with Amateur Radio?
73 de chris KG6VYD
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</pre>
</blockquote>
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