If anyone's wondering about the orbit, it's a geosynchronous but not geostationary orbit.<p>The geosynchronous part is so that they only need a few sats to cover their region, unlike GPS which is global and requires some 32 sats.<p>It's not an equatorial geostationary orbit so that receivers at higher latitudes (in Japan) will see a sat overhead instead of always over the equator. This is to deal with the "canyon" effect. Guaranteeing a bird overhead, rather than GPS's catch-as-catch-can, should definitely help signal reliability.<p>These will be further away than GPS, which are medium Earth orbit.<p>Some other info (including an animation) here:<p><a href="http://global.jaxa.jp/countdown/f18/overview/orbit_e.html" rel="nofollow">http://global.jaxa.jp/countdown/f18/overview/orbit_e.html</a><p>It should also be useful in Australia and parts between. They will also park spare sats in geostationary equatorial orbits.<p>It's a bit inspired, I think, by the Molniya orbit, another technique to get long-duration high-latitude overflight:<p><a href="http://en.wikipedia.org/wiki/Molniya_orbit" rel="nofollow">http://en.wikipedia.org/wiki/Molniya_orbit</a>
Very interesting. Actually, something similar happened in the US back in 2000, when Clinton turned off something called "Selective Availability" in the US. This program deliberately degraded civilian GPS signals. After SA was turned off, we went from a GPS system that was accurate to a football field-type area to one that is accurate to a tennis-court ish area.<p>Read more: <a href="http://www.gps.gov/systems/gps/modernization/sa/" rel="nofollow">http://www.gps.gov/systems/gps/modernization/sa/</a>
This seems to be similar to the usage of WAAS in the US (<a href="http://en.wikipedia.org/wiki/Wide_Area_Augmentation_System" rel="nofollow">http://en.wikipedia.org/wiki/Wide_Area_Augmentation_System</a>), just on a smaller geographic scale. One of the bigger sources of error in GPS today is due to various atmospheric effects that bend the signal and increase the signals propagation delay. A ground stations in a known position can generate correction for the errors but the farther it's from the ground station the less useful the correction is. I've seen GPS systems used in farming applications that use a local tower that can provide corrections to give a very accurate position for the local area.
GPS is a misnomer, it should be JPS, Japan Positioning System, nothing global to see here folks. It is unfortunate that the article does not stress that this system is only useful in Japan; especially with the conclusion that many nations will be watching the results given the "range of promised applications <i>[range of use, certainly not geographic range]</i> and relatively low cost." That being said I am interested to see how the experiment with atomic clockless birds goes. One of the most overlooked features of GPS is time transfer.
I'm having trouble understanding the practical consequences of this project.<p>If I would be in Japan, with a regular, GPS-tuned/understanding device, would I get better service? Or would I need a special device, that'd be able to understand GPS+"JPS"?<p>The part where they transmit correction data to the satellites also confuse me, if that's what they're doing; It's not the same as the United States Global Positioning Service if that'd be the case, right? For what I've understood, the GPS doesn't need a constant feeding of data from ground stations - it's ""simply"" a bunch of satellites sending out the current time from their on-board atomic clocks.
Having moved to Tokyo last year, I'm really hopeful for more accurate altitude data. Much of Tokyo is under and above ground level, and I wish the altitude data were accurate enough to determine which floor I'm on.<p>Perhaps Bluetooth LE and beacons will eventually allow more accurate elevation info.
Wow, I didn't know GPS technology was even capable of that accuracy. It would be interesting to see it used in augmented reality as well as the examples from the article. You could actually have shared virtual objects positioned out in the world.
If you combined cm accuracy in cell phone tracking and a armed quadcopter, and hacked the phone company, you could build a handy remote killing device.
What a wonderful example for the "standards" xkcd: <a href="https://xkcd.com/927/" rel="nofollow">https://xkcd.com/927/</a><p>Many countries in these days try to build their own alternative to GPS, or in this example a extension for it. This for sure makes the location mor accurate and the systems are independant from the united states.<p>On the other hand for instance mobile phones have to implement all these systems and this makes them much more expensive and complicated. From my point of view it would be better to build up a universal international system. Yes, and I know this is nearly undoable.