[time-nuts] Re: Tonga effect on GPS

[Attila Kinali]

On Mon, 7 Feb 2022 12:46:47 -0800
Kevin Rowett <kevin at rowett.org> wrote:

> Can someone put the disturbance in perspective?  How much would this
> affect navigation, or timing, and how large (or small) is this disturbance 
> in magnitude as compared to other events (CMEs?)

Dual-frequency receivers: very little, as they can correct for
ionospheric delay directly (though not for the lensing effect).

Single frequency receivers quite a bit more. IIRC the delay variation
through the ionosphere is usually in the order of 10ns. Let's say
we double that due to the volcanic erruption. Assuming this shifts
all satellites in the worst way possible for the reciever (which it
clearly does not) that gives us a 10ns/3m shift. While not nothing,
for most applications this wouldn't be a big issue. Anything below
10m is not showing up on most naviagation systems (either they don't
care or they have compensation systems for the inaccuracy of GPS anyways)
and for timining systems, that would get smoothed out by the OCXO and
give only a bump of a few ns which would be below the noise for the
most common applications. 

But it might be fun to check the IGS data in a month to see how it affected
the ionosphere and through that the PVT solution of various stations.

			Attila Kinali

-- 
The driving force behind research is the question: "Why?"
There are things we don't understand and things we always 
wonder about. And that's why we do research.
		-- Kobayashi Makoto