"Scott in Aztlan" wrote in message
...
Suppose you were participating in a search for a hidden radio transmitter,
only
instead of the usual radio receiver with a directional antenna you have a
receiver with an omnidirectional antenna and a GPS receiver. As you wander
---snip---

Can someone point me in the right direction?

Just follow the strongest radio signal. ;-)

Scott in Aztlan wrote:

Suppose you were participating in a search for a hidden radio transmitter, only
instead of the usual radio receiver with a directional antenna you have a
receiver with an omnidirectional antenna and a GPS receiver. As you wander
around, you collect positions from the GPS and signal strength values at those
positions from the radio; your goal is to crunch these data points into an
estimate of the transmitter's location.

Clearly you could use trilateration with any 3 of the data points and get an
estimate, but how would you make use of the fact that you have an arbitrary
number of data points?

If I understand clearly you are interested in locating an RF source which
has nothing to do with GPS by using RF receivers and nondirectional antennae.
Trilateration is only of value if one can establish accurate timing distances,
synchronized between all receivers.

If you used directional RF antennae, then, in conjunction with receiver positions
determined by GPS receivers, you could simply triangulate to estimate the RF
source position.

Isn't there some algorithm which, the more data points it
is given, the better its estimate gets (similar to the way you can average a
series of position readings taken from a stationary GPS receiver to compensate
for the effects of SA)?

Of course SA was permanently discontinued more than three year ago.

Interagency GPS Executive Board (IGEB) - Special Statement
http://www.ostp.gov/NSTC/html/pdd6.html
http://www.igeb.gov/sa.shtml

Presidential Policy & PRESIDENTIAL DECISION DIRECTIVE NSTC-6
http://gps.faa.gov/gpsbasics/PresPolicy-text.htm
http://www.peterson.af.mil/GPS_Suppo...ts/gps_pdd.htm

Selective Availability
http://gps.faa.gov/gpsbasics/SA-text.htm

Joint Program Office
http://gps.faa.gov/gpsbasics/JPO-text.htm

Scott in Aztlan wrote:

Suppose you were participating in a search for a hidden radio transmitter, only
instead of the usual radio receiver with a directional antenna you have a
receiver with an omnidirectional antenna and a GPS receiver. As you wander
around, you collect positions from the GPS and signal strength values at those
positions from the radio; your goal is to crunch these data points into an
estimate of the transmitter's location.

Clearly you could use trilateration with any 3 of the data points and get an
estimate, but how would you make use of the fact that you have an arbitrary
number of data points? Isn't there some algorithm which, the more data points it
is given, the better its estimate gets (similar to the way you can average a
series of position readings taken from a stationary GPS receiver to compensate
for the effects of SA)?

Can someone point me in the right direction?

A system for integrating GPS with direction finding has been out for a
few years now. Utilizing Doppler Direction finding equipment, the
heading of the Doppler array, along with the Lat Long of the monitoring
station is sent in a packet burst and superimposed on a map. When you
have 2-3 of these stations submitting this data in real time, you get a
practically instantaneous triangulation on the location of the transmitter.

The Agrelo Doppler units that were available several years ago, had this
capability.

Andy
WD4KDN



--
An armed man is a citizen, an unarmed man is a subject.
An armed society is a polite society.

Assuming your concept was valid, i.e. signal strength was a function of distance by
some formula (inverse square), the approach to follow is called least squares. Look
around for additional info with that terminology.

- jlw

Scott in Aztlan wrote:

Suppose you were participating in a search for a hidden radio transmitter, only
instead of the usual radio receiver with a directional antenna you have a
receiver with an omnidirectional antenna and a GPS receiver. As you wander
around, you collect positions from the GPS and signal strength values at those
positions from the radio; your goal is to crunch these data points into an
estimate of the transmitter's location.

Clearly you could use trilateration with any 3 of the data points and get an
estimate, but how would you make use of the fact that you have an arbitrary
number of data points? Isn't there some algorithm which, the more data points it
is given, the better its estimate gets (similar to the way you can average a
series of position readings taken from a stationary GPS receiver to compensate
for the effects of SA)?

Can someone point me in the right direction?

Thanks!

--
Friends don't let friends shop at Best Buy.

"Jerry L. Wahl" wrote in
:

Assuming your concept was valid, i.e. signal strength was a function
of distance by some formula (inverse square), the approach to follow
is called least squares. Look around for additional info with that
terminology.

- jlw


I participate in a lot of transmitter hunts. I hadn't thought of it but
you are on to something. I wouldn't recommend finding a transmitter
using the method he wants to do it in, that would take too much time. He
would also need an attenuator to prevent full scale readings.

If he wants to hunt with an omni, all he needs really is a step
attenuator and a receiver with an S-meter. Leave the GPS at home.

A faster method is with a directional or null antenna, attenuator, map,
protractor, and possibly compass so he can put the headings on the map
more accurately.

I was thinking of using GPS too, but here is how I would do it. I have a
4 antenna doppler array that gives real time headings. The array is
mounted on my vehicle. The doppler unit sends four bit BCD to a 16 LED
heading indicator.

I would pull the BCD readings and send them to a notebook computer with a
mapping program installed and the GPS connected. The program code would
take the heading from the doppler unit, the receiving position from the
GPS, and superimpose it on the map. The code would also have an
"averaging algorithem" to throw out bad heading do to reflections and
such.

I would only do something like this to show how nifty you could find a
transmitter. Will I do this? Probably not, I already do it in my head.


KB7ADL

I also wanted to give this link: www.homingin.com

KB7ADL



"Vince Fiscus, KB7ADL" wrote in
ink.net:

"Jerry L. Wahl" wrote in
:

Assuming your concept was valid, i.e. signal strength was a function
of distance by some formula (inverse square), the approach to follow
is called least squares. Look around for additional info with that
terminology.

- jlw


I participate in a lot of transmitter hunts. I hadn't thought of it
but you are on to something. I wouldn't recommend finding a
transmitter using the method he wants to do it in, that would take too
much time. He would also need an attenuator to prevent full scale
readings.

If he wants to hunt with an omni, all he needs really is a step
attenuator and a receiver with an S-meter. Leave the GPS at home.

A faster method is with a directional or null antenna, attenuator,
map, protractor, and possibly compass so he can put the headings on
the map more accurately.

I was thinking of using GPS too, but here is how I would do it. I
have a 4 antenna doppler array that gives real time headings. The
array is mounted on my vehicle. The doppler unit sends four bit BCD
to a 16 LED heading indicator.

I would pull the BCD readings and send them to a notebook computer
with a mapping program installed and the GPS connected. The program
code would take the heading from the doppler unit, the receiving
position from the GPS, and superimpose it on the map. The code would
also have an "averaging algorithem" to throw out bad heading do to
reflections and such.

I would only do something like this to show how nifty you could find a
transmitter. Will I do this? Probably not, I already do it in my
head.


KB7ADL

I also wanted to give this link: www.homingin.com

KB7ADL



"Vince Fiscus, KB7ADL" wrote in
ink.net:

"Jerry L. Wahl" wrote in
:

Assuming your concept was valid, i.e. signal strength was a function
of distance by some formula (inverse square), the approach to follow
is called least squares. Look around for additional info with that
terminology.

- jlw


I participate in a lot of transmitter hunts. I hadn't thought of it
but you are on to something. I wouldn't recommend finding a
transmitter using the method he wants to do it in, that would take too
much time. He would also need an attenuator to prevent full scale
readings.

If he wants to hunt with an omni, all he needs really is a step
attenuator and a receiver with an S-meter. Leave the GPS at home.

A faster method is with a directional or null antenna, attenuator,
map, protractor, and possibly compass so he can put the headings on
the map more accurately.

I was thinking of using GPS too, but here is how I would do it. I
have a 4 antenna doppler array that gives real time headings. The
array is mounted on my vehicle. The doppler unit sends four bit BCD
to a 16 LED heading indicator.

I would pull the BCD readings and send them to a notebook computer
with a mapping program installed and the GPS connected. The program
code would take the heading from the doppler unit, the receiving
position from the GPS, and superimpose it on the map. The code would
also have an "averaging algorithem" to throw out bad heading do to
reflections and such.

I would only do something like this to show how nifty you could find a
transmitter. Will I do this? Probably not, I already do it in my
head.


KB7ADL

Vince Fiscus, KB7ADL wrote:

I participate in a lot of transmitter hunts.

If he wants to hunt with an omni, all he needs really is a step
attenuator and a receiver with an S-meter. Leave the GPS at home.

I was thinking of using GPS too, but here is how I would do it. I have a
4 antenna doppler array that gives real time headings. The array is
mounted on my vehicle. The doppler unit sends four bit BCD to a 16 LED
heading indicator.


I believe there is a kit you can build:

http://www.ramseyelectronics.com/cgi...ction&key=DDF1

Vince Fiscus, KB7ADL wrote:

I participate in a lot of transmitter hunts.

If he wants to hunt with an omni, all he needs really is a step
attenuator and a receiver with an S-meter. Leave the GPS at home.

I was thinking of using GPS too, but here is how I would do it. I have a
4 antenna doppler array that gives real time headings. The array is
mounted on my vehicle. The doppler unit sends four bit BCD to a 16 LED
heading indicator.


I believe there is a kit you can build:

http://www.ramseyelectronics.com/cgi...ction&key=DDF1

"Jerry L. Wahl" wrote in
:

Assuming your concept was valid, i.e. signal strength was a function
of distance by some formula (inverse square), the approach to follow
is called least squares. Look around for additional info with that
terminology.

- jlw


I participate in a lot of transmitter hunts. I hadn't thought of it but
you are on to something. I wouldn't recommend finding a transmitter
using the method he wants to do it in, that would take too much time. He
would also need an attenuator to prevent full scale readings.

If he wants to hunt with an omni, all he needs really is a step
attenuator and a receiver with an S-meter. Leave the GPS at home.

A faster method is with a directional or null antenna, attenuator, map,
protractor, and possibly compass so he can put the headings on the map
more accurately.

I was thinking of using GPS too, but here is how I would do it. I have a
4 antenna doppler array that gives real time headings. The array is
mounted on my vehicle. The doppler unit sends four bit BCD to a 16 LED
heading indicator.

I would pull the BCD readings and send them to a notebook computer with a
mapping program installed and the GPS connected. The program code would
take the heading from the doppler unit, the receiving position from the
GPS, and superimpose it on the map. The code would also have an
"averaging algorithem" to throw out bad heading do to reflections and
such.

I would only do something like this to show how nifty you could find a
transmitter. Will I do this? Probably not, I already do it in my head.


KB7ADL