JimFram
Posts: 1
Joined: Sat Feb 04, 2017 5:35 pm

GPS Simulator/Emulator

Sat Nov 18, 2017 7:39 am

I am in need of a GPS Simulator for use in a underground location where a GPS signal is required for the device to work. I have been using devices that I have located from the internet although these GPS simulators are >$2,900-$32,0000. Can I somehow develop a GPS simulator that will generate four (4) GPS signals and program the Pi with a known location? The device needs to generate a GPS L1 RF signal 1575.42 MHz at a signal level of approx. -105dbm.

Any help and/or advice would be greatly appreciated.

Thanks!

Jim

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topguy
Posts: 3716
Joined: Tue Oct 09, 2012 11:46 am
Location: Trondheim, Norway

Re: GPS Simulator/Emulator

Sun Nov 19, 2017 10:57 pm

The Pi itself doesn't have GPS so you would have to add a GPS device anyway, but I dont understand what you are trying to do.
- Are you still going to try to use GPS to navigate underground ?
- Or do you just need to trick the Pi that it has a GPS signal ?

The Pi is going to read NMEA data from the GPS you will connect to it, but NMEA data is just text that is very easy to simulate.

ghans
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Location: Germany

Re: GPS Simulator/Emulator

Mon Nov 20, 2017 11:09 am

OP doesn't want the Pi to emulate a GPS dongle. OP wants the Pi to emulate a
GPS satellite ...

I assume OP has a bunch of cheap GPS navi systems lying around which would be totally
useful if there was a way to use them in OPs underground cave complex.

If i had to decide between designing a reliable "outdoor" navigation system and a GPS transmitter i would opt for a map and a compass.

ghans
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topguy
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Location: Trondheim, Norway

Re: GPS Simulator/Emulator

Mon Nov 20, 2017 12:06 pm

hm.. yeah that might make more sense.

Understanding that the location a GPS is reporting, comes from the minute differences in time the signal from each satellite reaches the receiver, and that the receiver also needs data about where each of the 24 satellites are at any moment in time. One can understand why these simulators costs what they do.

Depending on how deep his Batcave is, you can get GPS repeaters a bit cheaper: https://webstore.tri-m.com/gps-equipmen ... eater-kit/

hippy
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Joined: Fri Sep 09, 2011 10:34 pm
Location: UK

Re: GPS Simulator/Emulator

Mon Nov 20, 2017 1:22 pm

ghans wrote:
Mon Nov 20, 2017 11:09 am
OP doesn't want the Pi to emulate a GPS dongle. OP wants the Pi to emulate a
GPS satellite ...
In fact needs to generate the signals to fake a small, four satellite, constellation looking at the OP.

It is not my area of expertise and I would guess it's a pretty specialised field. I would expect it's one of those cases that if it were easy or cheap to do then people would be doing that. A quick search of t'internet did not show up any homebrew GPS transmitters.

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topguy
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Re: GPS Simulator/Emulator

Mon Nov 20, 2017 3:26 pm

hippy wrote:
Mon Nov 20, 2017 1:22 pm
A quick search of t'internet did not show up any homebrew GPS transmitters.
Just think about the possible security/safety implications if this was easy to do.

hippy
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Location: UK

Re: GPS Simulator/Emulator

Mon Nov 20, 2017 4:55 pm

I dug around and couldn't find anything low priced, not even systems using off-the-shelf SDR's. It's a whole new ballpark to hijacking heart rate monitor watches and faking radio time code signals which only need a coil of wire and a $1 micro.

I think we are safe from rogue CubeSats and miscreants on motorway bridges at least for now :D

beta-tester
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Re: GPS Simulator/Emulator

Mon Nov 20, 2017 8:20 pm

JimFram wrote:
Sat Nov 18, 2017 7:39 am
I am in need of a GPS Simulator for use in a underground location where a GPS signal is required for the device to work. I have been using devices that I have located from the internet although these GPS simulators are >$2,900-$32,0000. Can I somehow develop a GPS simulator that will generate four (4) GPS signals and program the Pi with a known location? The device needs to generate a GPS L1 RF signal 1575.42 MHz at a signal level of approx. -105dbm.

Any help and/or advice would be greatly appreciated.

Thanks!

Jim
sounds a little bit like "GPS Spoofing"... :?

is there no way to bypass the GPS receiver and feet the NMEA data to the device that is directly behind the GPS receiver?
so you do not need that fancy expensive high frequency stuff. then you only need to cut trace on the PCB of the GPS module serial output and inject simulated serial data to the consuming device.
Last edited by beta-tester on Sat Nov 25, 2017 8:50 pm, edited 2 times in total.
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rosbif69
Posts: 1
Joined: Sat Nov 25, 2017 4:35 pm

Re: GPS Simulator/Emulator

Sat Nov 25, 2017 4:38 pm

Funnily enough, I'd like one too. :-) I want to test my GPS programs in python, without having to leave the window open.

I've seen this:

https://www.youtube.com/watch?v=VqLSKPYKeXU

But the information isn't too detailed. It does seem to be near to what the OP is requesting though.

hippy
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Joined: Fri Sep 09, 2011 10:34 pm
Location: UK

Re: GPS Simulator/Emulator

Sat Nov 25, 2017 8:04 pm

rosbif69 wrote:
Sat Nov 25, 2017 4:38 pm
I've seen this: https://www.youtube.com/watch?v=VqLSKPYKeXU
That is using Bluetooth to provide faked location data for the mobile phone, rather than providing a faked satellite signal which the phone's GPS receiver can use. It is a clever idea but not quite the same.

It might be a solution for the original poster, but perhaps not; they haven't detailed what their receiving equipment is.

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