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bob1029 a day ago

I think techniques like BPS might be more viable.

https://www.nist.gov/publications/time-transfer-performance-...

https://www.jeffgeerling.com/blog/2025/bps-gps-alternative-n...

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adrian_b a day ago | parent | next [-]

The applications of BPS are entirely different.

BPS depends on terrestrial stations instead of satellites, like Loran, which was used in the past.

BPS is at least as easily jammed or disabled as GPS.

With the gravimeter discussed in the article, and with adequate maps, one can navigate autonomously, without depending on any external help.

Moreover, BPS appears to be intended to cover only continental USA. There are no plans to use radio frequencies that would allow global coverage, like Loran had in the past.

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WJW a day ago | parent [-]

> BPS depends on terrestrial stations instead of satellites, like Loran, which was used in the past.

> BPS is at least as easily jammed or disabled as GPS.

So which is it? Because LORAN was much harder to jam than GPS. The jamming resistance of any positioning system is mostly based on the ability to overpower the legitimate signals arriving at the receiving antenna. The problem with satellite based positioning systems is:

1. Satellites have relatively little power available to them, which makes their broadcasts rather weak. Terrestial transmitters can be much more powerful.

2. Satellites are very far away, which causes the received power to be very attenuated. Terrestial transmitters can be much closer.

There are many valid reasons to choose GNSS over terrestial approaches, but jamming resistance is not one of them.

Source: I was a weapons engineering officer for the Dutch Navy for many years and jammability of our positioning systems was a constant concern, to the point of ships being equipped with LORAN-C receivers well into the 2000s as a backup for GPS.

	▲	luma a day ago \| parent \| next [-]
		In an EW contested environment, anything relying on external RF signaling is subject to denial or spoofing. The war in Ukraine is teaching everyone a lot of lessons.
	▲	geerlingguy a day ago \| parent \| prev \| next [-]
		BPS would be substantially harder to jam, as the broadcast signal power would be local and in the many kW range (50+ kW transmitters, with multiple frequencies per city). GPS is one frequency (or a few if you use other countries' systems which has its own risks), with far lower signal strength.
	▲	c_o_n_v_e_x a day ago \| parent \| prev [-]
		>Terrestial transmitters can be much closer. Making them nice targets for the enemy

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rcxdude a day ago | parent | prev [-]

Still in principle vulnerable to jamming, even if less so than the fairly weak signal from GPS. Though I suspect there will be an emphasis on using a combination of techniques, instead of relying on any single one.