The question is, why should someone with low income but fully owned property NOT be allowed to live in it?

Because real estate is special. All real estate is owned by individuals through patent by the government. The point of real estate is to benefit society as a whole through development and wealth creation. Property taxes are a purposeful disincentive on "sitting" on a piece of valuable property.

Why isn't Creative's Zen line supported?

Because nobody who has a Zen has stepped up.

AMS gave datasheets. http://www.rockbox.org/wiki/AustriaMicrosystems

Sandisk gave dev boards and NO docs.

Nobody else gave squat.

To be pedantic WAAS is a differential system.

And to be overly pedantic for the GP, WAAS specifications don't meet the 1m/24/7 spec, but in practice it is sub meter 95% of the time.

Your vendor is likely confusing you (and perhaps themselves).

GPS horizontal positioning does not require a very precise model of the earth.

GPS vertical positioning does not require a very precise model of the earth.

The gotcha there is that GPS works in ellipsoidal heights, NOT elevation. The ellipsoid is a simplified model of the earth. Elevation is height above mean sea level if the sea reached where you are. The elevation of any point measured by GPS is a combination of the ellipsoidal height and a gravity map (if there were no land, no wind, no tides the sea would still be uneven due to uneven distribution of gravity potential) called a geoid model.

As for lock and initialization times - I routinely profile roads, in traffic, and have no trouble maintaining initialization. That and a Trimble R8 GNSS (R8 model III) can initialize FAR faster than 20 seconds.

Close.

Carrier tracking does not require a very precise model of the earth. Real Time Kinnematic GPS has been done for well over a decade with rather sane processing requirements. It also isn't unstable. So long as the L1 and L2 signal of five satellites are tracked one can initialize on the fly, and you only need to track four continuously to maintain said initialization.

Like differential (a code-base correction) kinnematic requires a base receiver and a rover receiver. They can either be in real time contact or the results can be post-processed. Differential and kinnematic both work by estimating the ionospheric delays, the difference is between tracking the long-period time code or tracking the short-period (19cm) carrier wave.

The problem isn't the GPS system. The problem is John Deere is trying to use the system at an accuracy (100% availability at 1m) greater than the specified [civilian] performance levels (95% availability at 7m).

While I can't speak as to the John Deere system in particular, most the Ag navigation systems are using WAAS on the low end and VRS RTK subscription systems on the high end.

Here in Ohio ODOT offers a reduced-fee reduced-accuracy VRS option for farmers, who don't need the sub-cm service.

They either had an asset over the drone or the US totally fucked up in the GPS antenna design.

GPS signals aren't in the "directional" frequencies. If they spoofed from orbit we'd know.

Not saying we'd publish, but we'd know. We'd not only know they could, we'd know where in what orbit their spoofing bird was.

Is letting that cat out of the bag worth one drone?

I'm guessing it was an implementation blunder.

I don't want to believe the Iranians have a GPS spoofing system so advanced it can migrate a GPS-initialized inertial system from a good solution to a spoofed solution.

I, therefore, rather suspect they jammed GPS long enough for the bird's INS to lose initialization, and then introduced a spoofed solution. I call this an implementation blunder because if this form of attack had been predicted one would respond in a "safe" manner to loss of GPS.

Question, though, is where was their spoofing equipment? Off-the-shelf GPS antennas from Trimble have quite good radio-absorbing ground planes. This is used to prevent GPS multipath when working near the ground, but would be quite effective at rejecting terrestrial transmission of false GPS signals. Does this mean Iran had one or more airplanes flying over the drone? Interesting, interesting.