[awesomeusername]

Seems fairly useless to me, for a few dollars I can sample the L1 frequency with a dumb device which has no idea of speed or altitude, and do the calcs with FOSS which is in the wild.

Basically a rule which inconveniences the honest and has zero impact on the bad dudes, whoever they are

[inigyou]

Have you done that?

[londons_explore]

I have. It works.

Used a huge amount of compute though and takes a long time to get a fix.

[minetest2048]

For L1 I think a raspberry pi can have a reasonably fast time to first fix, for offline processing you can go faster than real time. L2/L5 need large sampling rate and a pi is probably not fast enough.. unless if you ditch float32 processing and do 2 bit signal processing, a uni commercialized that: https://radionavlab.ae.utexas.edu/wp-content/uploads/2022/10...

[londons_explore]

Nearly all commercial GPS receivers use a 1 bit ADC. Ie. Just a comparator.

The sample rate isn't high either - 16Mhz IIRC.

[inigyou]

Maybe that's why nobody else does

[rescbr]

You can use a FPGA, like this 2013 project: http://www.aholme.co.uk/GPS/Main.htm

Or go old school (1991-1992): https://lea.hamradio.si/~s53mv/navsats/theory.html

So yeah, this regulation is absolutely an inconvenient measure.

[inigyou]

Have you done that?

[rescbr]

Nah, I live in a major city between two airports, under an airplane departure and a heli route. I can't really launch rockets or balloons from my home.

When I was at uni I didn't have the funds for this hobby unfortunately.

[minetest2048]

There's a strong indication that SpaceX does use software receiver in Falcon 9 and Starlink: when they didn't encrypt the downlink telemetry someone captured the signal and found some plain text: https://www.rtl-sdr.com/receiving-space-x-falcon-9-telemetry...

That plain text looks like what a software GNSS receiver outputs as its very verbose, and this paper: https://radionavlab.ae.utexas.edu/wp-content/uploads/2022/10... , a paper about a software receiver mentioned this:

> PpRx has been licensed through the Radionavigation Lab to multiple commercial companies, but notably a major aerospace company that uses the technology across their suite of advanced spacecraft and satellites. The SDR is deployed across the company’s mega-constellation of satellites used for broadband Internet