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Dual GPS smartphone (Navstar and Galileo) and will there be dual frequency GPS avionics?

I did a quick google.

Enhancing the accuracy of GPS point positioning by converting the single frequency data to dual frequency data

When radio waves propagate through the ionosphere they suffer an extra time delay. This time delay is a function of the total electron content (TEC) of the ionosphere. Since the ionosphere acts as a dispersive medium to GPS signals, dual-frequency (L1 at 1575.42 MHz, L2 at 1227.60 MHz) GPS receivers can eliminate (albeit to the first order) ionospheric delay through a linear combination of L1 and L2 observations

Single- versus Dual-Frequency Precise Point Positioning

Another lead

The improvement is only to the first order (i.e. not to the level of differential GPS where you rig up a GPS station on the ground) but that is way better than what is achieved in practice with WAAS/EGNOS. OTOH it appears that the computation needs time and there is where the tradeoff is if the receiver is continuously moving.

Looking back at the first post above, it sounds like the Galileo approach is to use E1/L1 + E5/L5 whereas the US Navstar approach is to use L1 + L2.

Administrator
Shoreham EGKA, United Kingdom

Receiving two constellations is not the same thing, AIUI. I was thinking of receiving L1 and L2 from any particular satellite concurrently.

GPS wiki

I had a Thuraya + L1 + L2 antenna on my plane. It was never used for GPS because there is no civilian L2 GPS receiver and later I replaced it with one which does Iridium, Thuraya and L1 and that one feeds the ADL150 nicely.

Found a pic:

The abandoned project was written up here.

Anyway, the point is that receiving and correlating L1 with L2 can be used to cancel out most of the atmospheric error because the frequencies are sufficiently different. Whether any avionics will appear in any of our lifetimes is another matter…

Administrator
Shoreham EGKA, United Kingdom

Of course, you have been able to buy the Garmin GLO for years.

EGKB Biggin Hill

Maybe @NCyankee knows more but I vaguely recall reading something about the errors being different for the different carrier frequencies and this enables a large degree of error cancellation. It also provides a better resistance to jamming because you have more uncorrelated signal to correlate, so to speak.

Administrator
Shoreham EGKA, United Kingdom

OK. How does multi constellation correct for ionospheric errors?

Sure, it is a future thing.

But it would remove the need for the WAAS and EGNOS ground monitoring stations and the geostationary satellites, the massive cost of those and the various points of failure. Transmitting the same signals from every GPS satellite is a much better solution.

Administrator
Shoreham EGKA, United Kingdom

Peter wrote:

But offering WAAS accuracy without WAAS satellite reception must be a huge advantage.

Perhaps if you live in Eastern Romania, Northern Finland or the Canaries. But doesn’t it just allow most of us, possibly, to do tomorrow what we already do today?

This dual frequency GPS stuff seems to have passed everyone by

It is perhaps as interesting to the main players (Garmin etc) as Galileo and Glonass of which neither is AFAIK supported.

But offering WAAS accuracy without WAAS satellite reception must be a huge advantage.

Administrator
Shoreham EGKA, United Kingdom

Presumably that phone supports Navstar (the original US GPS system) anyway, plus Galileo, and it reads like it is on Galileo it supports both frequencies. But would anyone make a chip which does just that?

No wonder that phone isn’t from Samsung, because they like to play games to collect wifi data

But it’s strange why one would want this in a phone, especially one without any special features (like a really good camera).

Administrator
Shoreham EGKA, United Kingdom

Dual frequency from a smart phone will have no impact, but the technology will enable procedures with vertical guidance equivalent to SBAS outside an SBAS service volume.

KUZA, United States
11 Posts
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