Electrical Engineering - Could I Build my own set of "GPS" like transmitters?

Author

Could I Build my own set of "GPS" like transmitters?

blarggstar

2005-08-17, 5:21 pm

I am actually a software guy and only know a little about electrical
engineering in general. (Since this crazy idea has come to mind, I am
teaching myself as much as I can.) I do not yet know what I can
realistically accomplish on my own.

I want to build a scaled down GPS system for an area about the size of
my house. I would like it to be accurate to about 1 or 2 cm.

It would incorporate 4 GPS like transmitters and a number of receiver
units. This would allow me to read the receiver unit's relative
position in area surrounded by these transmitters. I only care about
tracking within my house, and possibly right outside, but not any
further. NOTE: I do not care about global position, only relative to
my transmitter area.

Based off my limited knowledge of the real GPS, building my own doesn't
seem to be outside my technological capabilities.

This is based off these facts:
The real satellites use RF waves to send these psuedo-random data
streams and the unit compares its local copy of psuedo-random stream
with the "delayed" satellite streams. (Delayed due to large distance RF
waves have to travel.) This delay is used to calculate distance and
eventually exact position of the unit. Using four satalites, it can
triangulate position and calibrate it's own clock to be reasonably
accurate.

My transmitters would have to have very accurate clocks, but I could
also calibrate these as often as needed.

So, is this even possible? Is it too far fetched to even consider
trying? Yes, I expect it to be hard, but would a seasoned EE
profesional be able to pull this off?

Real GPS solutions that have sub-meter (let alone 1-2 cm) accuracy are
very expensive: $30k - $50k.

One other note, this system would be incorporated into a potentially
lucrative product, if it worked. It would be worth all the trouble it
would take to build.

Even further, does something like this exist allready? or would
someone be interested in building this for me? This is a small step to
my "real" idea, which has nothing to do with surveying, mapping, or any
other global positioning problems.

Thanks in advance and I hope this is the most appropriate group to be
posting in.

blarggstar

2005-08-17, 9:21 pm

Afterthougt: I should have posted this to sci.electronics.design

Sorry, I'm new here.

operator jay

2005-08-19, 1:21 am

"blarggstar" <blargg27@gmail.com> wrote in message
news:1124322172.332167.249730@o13g2000cwo.googlegroups.com...
> Afterthougt: I should have posted this to sci.electronics.design
>
> Sorry, I'm new here.
>

I know a place where you might find a great description of exactly what you
are thinking of. The Patent Office.

Jimmie

2005-08-19, 1:21 am

"blarggstar" <blargg27@gmail.com> wrote in message
news:1124309366.950881.264380@g49g2000cwa.googlegroups.com...
>I am actually a software guy and only know a little about electrical
> engineering in general. (Since this crazy idea has come to mind, I am
> teaching myself as much as I can.) I do not yet know what I can
> realistically accomplish on my own.
>
> I want to build a scaled down GPS system for an area about the size of
> my house. I would like it to be accurate to about 1 or 2 cm.
>
> It would incorporate 4 GPS like transmitters and a number of receiver
> units. This would allow me to read the receiver unit's relative
> position in area surrounded by these transmitters. I only care about
> tracking within my house, and possibly right outside, but not any
> further. NOTE: I do not care about global position, only relative to
> my transmitter area.
>
> Based off my limited knowledge of the real GPS, building my own doesn't
> seem to be outside my technological capabilities.
>
> This is based off these facts:
> The real satellites use RF waves to send these psuedo-random data
> streams and the unit compares its local copy of psuedo-random stream
> with the "delayed" satellite streams. (Delayed due to large distance RF
> waves have to travel.) This delay is used to calculate distance and
> eventually exact position of the unit. Using four satalites, it can
> triangulate position and calibrate it's own clock to be reasonably
> accurate.
>
> My transmitters would have to have very accurate clocks, but I could
> also calibrate these as often as needed.
>
> So, is this even possible? Is it too far fetched to even consider
> trying? Yes, I expect it to be hard, but would a seasoned EE
> profesional be able to pull this off?
>
> Real GPS solutions that have sub-meter (let alone 1-2 cm) accuracy are
> very expensive: $30k - $50k.
>
> One other note, this system would be incorporated into a potentially
> lucrative product, if it worked. It would be worth all the trouble it
> would take to build.
>
> Even further, does something like this exist allready? or would
> someone be interested in building this for me? This is a small step to
> my "real" idea, which has nothing to do with surveying, mapping, or any
> other global positioning problems.
>
> Thanks in advance and I hope this is the most appropriate group to be
> posting in.
>

GPS was first tested on the ground using "psuedolites".
The system you describe was actually built before GPS.

daestrom

2005-08-20, 1:21 pm

"blarggstar" <blargg27@gmail.com> wrote in message
news:1124309366.950881.264380@g49g2000cwa.googlegroups.com...
>I am actually a software guy and only know a little about electrical
> engineering in general. (Since this crazy idea has come to mind, I am
> teaching myself as much as I can.) I do not yet know what I can
> realistically accomplish on my own.
>
> I want to build a scaled down GPS system for an area about the size of
> my house. I would like it to be accurate to about 1 or 2 cm.
>
> It would incorporate 4 GPS like transmitters and a number of receiver
> units. This would allow me to read the receiver unit's relative
> position in area surrounded by these transmitters. I only care about
> tracking within my house, and possibly right outside, but not any
> further. NOTE: I do not care about global position, only relative to
> my transmitter area.
>
> Based off my limited knowledge of the real GPS, building my own doesn't
> seem to be outside my technological capabilities.
>
> This is based off these facts:
> The real satellites use RF waves to send these psuedo-random data
> streams and the unit compares its local copy of psuedo-random stream
> with the "delayed" satellite streams. (Delayed due to large distance RF
> waves have to travel.) This delay is used to calculate distance and
> eventually exact position of the unit. Using four satalites, it can
> triangulate position and calibrate it's own clock to be reasonably
> accurate.
>
> My transmitters would have to have very accurate clocks, but I could
> also calibrate these as often as needed.
>
> So, is this even possible? Is it too far fetched to even consider
> trying? Yes, I expect it to be hard, but would a seasoned EE
> profesional be able to pull this off?
>
> Real GPS solutions that have sub-meter (let alone 1-2 cm) accuracy are
> very expensive: $30k - $50k.
>
> One other note, this system would be incorporated into a potentially
> lucrative product, if it worked. It would be worth all the trouble it
> would take to build.
>
> Even further, does something like this exist allready? or would
> someone be interested in building this for me? This is a small step to
> my "real" idea, which has nothing to do with surveying, mapping, or any
> other global positioning problems.
>
> Thanks in advance and I hope this is the most appropriate group to be
> posting in.

Just a thought...

Since the transmitters are fixed in/around the home, they could all be
driven from a single 'clock' somewhere. Of course the signals from the
clock to each transmitter would be received by the xmitters at different
times, so each would not *really* be at the same time. But once this
*fixed* time difference is known/calculated, any receiver could 'learn' the
difference and properly compensate.

daestrom

LinkBot