1 GPS Implementation of a twin scenario

On 9/3/17 9:31 AM, Gary Harnagel wrote:

>	On Saturday, September 2, 2017 at 8:33:52 AM UTC-6, Nicolaas Vroom wrote:

>>	For GPS clocks you can do a simular experiment. One GPS clock you keep on earth and one other you bring in orbit for 1 year and you bring it back.

>	That would be a nice experiment, but it cannot be done.

No. But one can certainly do a similar experiment:

Put the GPS satellite into orbit and when it is directly overhead, have it send a time signal to a receiver and clock on the ground. Wait roughly a year, and when it is again directly overhead have it send another time signal. Any propagation effects will be the same for the two signals, so the ground-measured time interval between the received signals should be compared to the satellite-measured time difference between the data contained in the signals. As the GPS is operational, one must of course correct for the modification of the satellite clock divider and for the clock offsets uploaded to the satellite, because the experiment needs to compare IDENTICAL atomic clocks.

The GPS performs this experiment daily, with the result that the modified satellite clock displays the same time interval as GPS time, to within the clock drift. That directly implies that a standard clock in the satellite would display a longer elapsed proper time between signals than a clock on earth's geoid, by roughly 38 microseconds per day.

With a PC, a GPS interface that costs < $100, and a bit of custom software, you could perform this experiment in your own home (using GPS time as the ground clock). Be sure to get a GPS interface that lets the PC read all GPS messages, because the software will need to monitor the daily uploaded clock offsets. Good software could perform the experiment independently for each GPS satellite, not just one. Use a UPS as the PC must be alive for the entire duration of the experiment. Indeed, I believe a Raspberry Pi could do this as well as any PC.

Hmmmm. There might well be a GPS monitoring webpage that already does all that....

Tom Roberts Click here to Reply

2 GPS Implementation of a twin scenario

>

Put the GPS satellite into orbit and when it is directly overhead, have it send a time signal to a receiver and clock on the ground. Wait roughly a year, and when it is again directly overhead have it send another time signal. Any propagation effects will be the same for the two signals, so the ground-measured time interval between the received signals should be compared to the satellite-measured time difference between the data contained in the signals. As the GPS is operational, one must of course correct for the modification of the satellite clock divider and for the clock offsets uploaded to the satellite, because the experiment needs to compare IDENTICAL atomic clocks.

Which would be obviously present in better, imagined world obeying Great Guru and your bunch of idiots. In the real world, however, with real clocks, your Shit's possibilities of confirming itself are limited:(

3 GPS Implementation of a twin scenario

>	That directly implies that a standard clock in the satellite would display a longer elapsed proper time between signals than a clock on earth's geoid, by roughly 38 microseconds per day.

You mean shorter, not longer. The lower curvature gradient WINS over the motion/speed. (the GPS enters the future of Earth's geoid)

>	With a PC, a GPS interface that costs < $100, and a bit of custom software, you could perform this experiment in your own home (using GPS time as the ground clock). Be sure to get a GPS interface that lets the PC read all GPS messages,

That's NMEA, serial. Piece of cake. Even something like this echo COM1 > CON

>

because the software will need to monitor the daily uploaded clock offsets. Good software could perform the experiment independently for each GPS satellite, not just one. Use a UPS as the PC must be alive for the entire duration of the experiment. Indeed, I believe a Raspberry Pi could do this as well as any PC.

Actually you can just write a simple script.

>	Hmmmm. There might well be a GPS monitoring webpage that already does all that.... Tom Roberts

See. The only requirement is to interpret the received converted from NMEA.

sat -> data -> receiver -> NMEA -> application layer

4 GPS Implementation of a twin scenario

>	Which would be obviously present in better, imagined world obeying Great Guru and your bunch of idiots. In the real world, however, with real clocks, your Shit's possibilities of confirming itself are limited

You can see those 38 microseconds using an oscilloscope. How would you explain that? Did you ever heard about ie dynamic/static laser scattering, whereas autocorrelation (in time) is used, with tau varying from days to milliseconds and such, depending on your test particles. You are an idiot with a mouth.

5 GPS Implementation of a twin scenario

> >	Use a UPS as the PC must be alive for the entire duration of the experiment. Indeed, I believe a Raspberry Pi could do this as well as any PC.

>	Actually you can just write a simple script.

I personally would prefer a piece of dedicated hardware over a PC.

You might want to look into BeagleBone Black as a possible alternative to Netduino/Arduino/Raspberry PI. These sorts of projects tend to balloon far beyond their original limited scope, and BBB has the most capable hardware.

I started a Netduino project which just kept growing like Topsy, and after two years abandoned it because the platform just couldn't keep up with my demands. The interpreted code in particular entailed a huge performance overhead. Arduino and Raspberry PI have advantages of a large community of users to help out. Netduino and BBB have relatively small communities.

Just sharing a few thoughts, not taking any hard positions. There are advantages and disadvantages to each approach.

6 GPS Implementation of a twin scenario

Nope. The GPS satellite clocks have modified dividers so their chip clocks tick at 10.22999999543 MHz while signals are received on the ground with a frequency of 10.23000000000 MHz. A chip clock in the satellite with a standard divider would tick at the latter rate, and thus experience MORE elapsed proper time between those signals than a clock on the geoid.

Tom Roberts

7 GPS Implementation of a twin scenario

>	Nope. The GPS satellite clocks have modified dividers so their chip clocks tick at 10.22999999543

According to The Shit of Great Einstein. But according to real clock of this satellite, it's 10.23

8 GPS Implementation of a twin scenario

9 GPS Implementation of a twin scenario

>	On Tuesday, September 5, 2017 at 4:46:05 PM UTC-5, Evan Grass wrote:

>> >	Use a UPS as the PC must be alive for the entire duration of the experiment. Indeed, I believe a Raspberry Pi could do this as well as any PC.

>>	Actually you can just write a simple script.

>	I personally would prefer a piece of dedicated hardware over a PC.

What part of NMEA serial communication you didn't understand. And forget Arduino and crap like that. Those are for novices and not even amateurs.

10 GPS Implementation of a twin scenario

>	On 9/5/17 9/5/17 4:46 PM, Evan Grass wrote:

>>	Tom Roberts wrote:

>>>	That directly implies that a standard clock in the satellite would display a longer elapsed proper time between signals than a clock on earth's geoid, by roughly 38 microseconds per day.

>>	You mean shorter, not longer.

>

Nope. The GPS satellite clocks have modified dividers so their chip clocks tick at 10.22999999543 MHz while signals are received on the ground with a frequency of 10.23000000000 MHz. A chip clock in the satellite with a standard divider would tick at the latter rate, and thus experience MORE elapsed proper time between those signals than a clock on the geoid. Tom Roberts

Not sure it is like that. You never see the spectrum of a HF carrier?? Does not really matter ass that difference is anyway BELOW the detection envelope. Even as such, IFF the circuitry were clocked by the ADJUSTED frequency, although there is no obvious reason, then that should talk in synch, accordingly. Think again.