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Comment by gchadwick | Hacker News Reader

It would be interesting to know of everything that uses GPS what % of use is purely for a very accurate synchronised time source vs uses that actually require the location aspect.

The article states 'The researchers found that the largest benefit, valued at $685.9 billion, came in the "telecommunications" category, including improved reliability and bandwidth utilization for wireless networks'. I wonder if location is actually required for these purposes or it's purely the synchronised time source (clearly a useful thing to have when building communication systems).

Edit: Ah the question is answered from another part of the article 'Wireless technology continues to evolve in ways that increase its reliance on highly precise timing, which in turn increases reliance on GPS.'

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The article mentions only GPS. Most modern receivers can use multiple systems for redundancy; GPS, GLONASS, Galileo, BeiDou. They can also provide accurate timing. https://gssc.esa.int/navipedia/index.php/Time_References_in_...

It's not clear if they use GPS as synonym for all available GNSS or is the study GPS only?

EDIT: I skimmed the document. The underlying assumption seems to be that US based industries don't have or don't use multi-constellation capability.

>In looking across the many sectors and applications that require GPS’s accuracy and precision, it becomes clear that GPS has some attributes of a utility. The signal is a public good and service provided by the U.S. government that enables productivity, quality, and efficiency benefits that would not otherwise be possible. For many years, it was the only comprehensive PNT signal available. Signals are now available from GLONASS (Russia), Galileo (Europe), and BeiDou (China). The global marketplace means that many devices are increasingly capable of receiving signals from multiple constellations. In the United States, however, critical infrastructure, industries, and applications leverage the GPS signal.

And a ton of older GPS-only hardware is still perfectly reliable and relevant. The recent week number roll-over forced some of the more decrepit junk to be replaced, but those with passable WNRO support are still in service despite being single-constellation.

It'll be a long time before multi-constellation receivers are the norm, and even longer before they displace the majority of critical timing receivers and reference stations and stuff.

Products like [1] consider concurrent GPS+GLONASS tracking a paid upgrade.

However, they also have 'holdover performance' allowing them to remain accurate for several hours without a GPS signal.

[1] https://www.microsemi.com/product-directory/carrier-grade-nt...

Similar product from Oscilloquartz has optional GNSS kit with GPS/GLONASS/BEIDOU/GALILEO

Location may be used during setup, but only timing is used during normal operation.

Long version: When a new site is installed from nothing, it doesn't even have a name in the database yet, so it gets a sequential number. If several sites are being commissioned at the same time, the techs need a way to establish which one they're talking to. Querying the GPS timing module for its location is a good way to be sure you're not mixing something up.

But the site timing antenna is not necessarily on or even near the tower itself, they could be a hundred feet away. So the location used for location-critical services is actually surveyed in a separate step and programmed in as a site parameter that does not change. It's not dynamically derived from GPS during operation.

Well, you could consider things like the Google Spanner database, that uses gps timing to do atomic commits across datacenters. Since this powers many of googles services (Gmail etc.), the fallout would potentially be massive on IT infrastructure.

You might be able to use the 1Hz IRIG H code from WWV and WWVB to discipline a crystal oscillator to get a clean 10MHz.

AFAIK this isn't how it works; the GPS provides a reference so the skew of the crystal can be measured as it drifts.

That's literally what "discipline a crystal oscillator" means. You measure and then correct the skew.

The crystal provides a local reference with low phase-noise, and the long-time-constant disciplining provides reasonable holdover performance.

Thanks, I wasn't familiar with the jargon or the electronics.

The original post said "might" but it seems that's exactly what cell sites use (GPSDOs).

Right, a normal cell site would use the 10MHz or 1 pulse per second from a GPS receiver to discipline their own oscillators. GPS could go out for a few minutes and everything would still work just fine. Anything past that and it's all dependent on how stable their oscillator is over time when it's free running.

The WWV and WWVB atomic clock radio stations have 1Hz reference frequencies that might be stable enough to be your 1PPS reference if you designed your GPSDO to accept an external 1PPS.

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