9 ms·

The same GPS the US Government reserves the right to reduce the precision when they feel like it? Seems risky idea to assume they will never do this.

wffurr 7y ago
I would hope aircraft would have multiband receivers that also support GLONASS, Galileo, and BeiDou. There's also Japan's QZSS and the regional Indian IRNSS.
- gsich 7y ago
  Probably depends on how old the stuff is.
kevstev 7y ago
Isn't low precision something like +/- 15 feet? For ATC, that seems more than good enough when they keep jets a mile+ apart. It just needs to be more precise than radar.
- Johnny555 7y ago
  The government claims that they won't enable selective availability any more (which is less useful as a protective mechanism anyway since multi-protocol receivers can use GPS / Galileo / GLONASS / Beidou). But if SA was enabled: Before it was turned off on May 2, 2000, typical SA errors were about 50 m (164 ft) horizontally and about 100 m (328 ft) vertically https://en.wikipedia.org/wiki/Error_analysis_for_the_Global_Positioning_System#Selective_availability https://en.wikipedia.org/wiki/Error_analysis_for_the_Global_...
- jomoio 7y ago
  There are also ground based systems at airports which increase reliability / integrity for things like simultaneous parallel approaches. [1] says to within +/- 1m horizontal and vertical. [1] https://www.skybrary.aero/index.php/Ground_Based_Augmentation_System_(GBAS) https://www.skybrary.aero/index.php/Ground_Based_Augmentatio...
sparker72678 7y ago
This isn't about using GPS as the only navigation aid in an airplane. It's about augmenting the current air traffic system with additional, more accurate data to help manage airspace. ADS-B doesn't change anything about how a plane navigates. That's still done with a plethora of redundant instruments, all working together.
iwalton3 7y ago
That is known as Selective Availability and according to the US Government there is no intention of enabling it again [1]. New GPS satellites are apparently being built without the Selective Availability capability [2]. [1] https://www.gps.gov/systems/gps/modernization/sa/faq/#on https://www.gps.gov/systems/gps/modernization/sa/faq/#on [2] https://archive.defense.gov/releases/release.aspx?releaseid=11335 https://archive.defense.gov/releases/release.aspx?releaseid=...
throw0101a 7y ago
> reduce the precision GPS satellites will not have the hardware to do selective availability in GPS III, which are currently being launched: * https://en.wikipedia.org/wiki/Error_analysis_for_the_Global_Positioning_System#Selective_availability https://en.wikipedia.org/wiki/Error_analysis_for_the_Global_...

wffurr 7y ago

I would hope aircraft would have multiband receivers that also support GLONASS, Galileo, and BeiDou. There's also Japan's QZSS and the regional Indian IRNSS.

gsich 7y ago
Probably depends on how old the stuff is.

kevstev 7y ago

Isn't low precision something like +/- 15 feet? For ATC, that seems more than good enough when they keep jets a mile+ apart. It just needs to be more precise than radar.

Johnny555 7y ago
The government claims that they won't enable selective availability any more (which is less useful as a protective mechanism anyway since multi-protocol receivers can use GPS / Galileo / GLONASS / Beidou). But if SA was enabled: Before it was turned off on May 2, 2000, typical SA errors were about 50 m (164 ft) horizontally and about 100 m (328 ft) vertically https://en.wikipedia.org/wiki/Error_analysis_for_the_Global_Positioning_System#Selective_availability https://en.wikipedia.org/wiki/Error_analysis_for_the_Global_...
jomoio 7y ago
There are also ground based systems at airports which increase reliability / integrity for things like simultaneous parallel approaches. [1] says to within +/- 1m horizontal and vertical. [1] https://www.skybrary.aero/index.php/Ground_Based_Augmentation_System_(GBAS) https://www.skybrary.aero/index.php/Ground_Based_Augmentatio...

sparker72678 7y ago

This isn't about using GPS as the only navigation aid in an airplane. It's about augmenting the current air traffic system with additional, more accurate data to help manage airspace. ADS-B doesn't change anything about how a plane navigates. That's still done with a plethora of redundant instruments, all working together.

iwalton3 7y ago

That is known as Selective Availability and according to the US Government there is no intention of enabling it again [1]. New GPS satellites are apparently being built without the Selective Availability capability [2]. [1] https://www.gps.gov/systems/gps/modernization/sa/faq/#on https://www.gps.gov/systems/gps/modernization/sa/faq/#on [2] https://archive.defense.gov/releases/release.aspx?releaseid=11335 https://archive.defense.gov/releases/release.aspx?releaseid=...

throw0101a 7y ago

> reduce the precision GPS satellites will not have the hardware to do selective availability in GPS III, which are currently being launched: * https://en.wikipedia.org/wiki/Error_analysis_for_the_Global_Positioning_System#Selective_availability https://en.wikipedia.org/wiki/Error_analysis_for_the_Global_...