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Optimism about food production, and info-geeking - Input Junkie
June 7th, 2013
07:57 am

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Optimism about food production, and info-geeking
The article is about improved farming techniques, but what caught my eye is:
Using a signal-processing scheme known as real-time kinematics*, or RTK, they can boost the accuracy of a GPS reading from about 3 meters to within just a few centimeters.
As I recall, the public GPS signal is deliberately obfuscated by the US government so that the military can have more accuracy than anyone else. Update-- it turns out I was right, but it's old news: signal degradation was turned off May 1, 2000.

That was one of the reasons there's a European satellite system in progress.

I hadn't heard that there are also planned Chinese, and Indian GPSs, and a Russian system-- GLONASS-- in operation. Correction about GLONASS thanks to ckd.

I don't have a feeling for how many GPSs would be needed in some theoretical sense to get enough redundancy, but one seems kind of skimpy.

Anyway, at least I was right about one thing-- we're getting more and more information from less data, this is a very cool trend, and I'm still not seeing science fiction about it. Or have I missed some?

*link added

First link thanks to andrewducker.

This entry was posted at http://nancylebov.dreamwidth.org/1009718.html. Comments are welcome here or there. comment count unavailable comments so far on that entry.

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From:ckd
Date:June 7th, 2013 02:39 pm (UTC)
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Not only has Selective Availability been turned off, newer GPS satellites don't even have the ability to turn it back on; it is now a permanent change.

(Minor correction: it was turned off in 2000, not 2001.)

The Russian system, GLONASS, is already in full operation; many newer receivers (including those in smartphones like the latest iPhone models and the Nexus 4) will use both GPS and GLONASS satellites to get faster and better position fixes than using either system alone would.
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From:nancylebov
Date:June 7th, 2013 03:47 pm (UTC)
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Article updated on both points. Thank you.

Edited at 2013-06-07 03:48 pm (UTC)
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