Quadcopters rarely carry radar altimeters, so the altimeter data comes from one of two possible sources:

1) barometric pressure.
2) GPS

The former requires correction for current air temperature and pressure, a process that pilots accomplish by setting a reported value in their altimeter and verifying the displayed altitude against known airport elevation. Quad pilots not operating at an airport with a reported "altimeter setting" are likely to make any adjustment by setting current altitude to "0" (AGL). If you start flying on a hilltop, then any flight that goes below that hilltop will become negative. If you fail to set the pressure altitude to 0 before taking off, you can easily have a negative elevation for the entire time of the flight. The quad flight management will create its own "AGL" by subtracting the starting altitude, but since the pilot may want to know MSL based on a calibrated pressure it won't convert the recorded telemetry.

If it is a GPS elevation, you should know that most GPS 3D data reports neither "MSL" nor "AGL" but "EHT" -- ellipsoid height. That is, the elevation above a reference ellipsoid that approximates the surface of the earth but does not equal it. It is quite possible to have an EHT of -49.5 feet and still be above ground level.

Almost. They say "over congested areas OF cities ...". The difference is that your version defines "congested area" as "cities..." while the correct version leaves "congested" as undefined but limits the rule to congested areas of cities, etc.

Also, you forgot to include the rules for helicopters.

Occam's Razor says that the most likely thing is the probably true thing. Is it easier for someone to alter the binary data of a telemetry log without detection, or for someone to lie about the altitude he thinks something was flying at? Given that people are bad at estimating altitudes of things that are flying overhead, and the stability of the quad depends on the position/inertial data being correct, I'd say the latter is probably a more accurate representation of the truth.

It will be a he-said/he-said, and it is well known that untrained persons have little ability to judge the altitudes of airborne objects. Even pilots have difficulty, since most of their experience is from looking down at the ground and not looking up at something small overhead. Both parties will have been sworn, and if you want to automatically assume that one is lying despite having telemetry as evidence, then you need to assume both are.

People who have never flown quadcopters should not comment on quadcopter flying. One pellet being hit by (not hitting) a prop on a quad is sufficient to damage it and cause the quad to fail.

You are shooting at a relatively slow moving target that has considerable mass and any projectile that is going to cause damage must be moving relatively fast. When quad shooting, you are shooting at parts of the quad that are rapidly moving and fragile, so all the projectile has to do is be in the path.

And lots of comments from people who have never touched a quad claiming that is impossible.

The laws do not refer to residential or non-residential areas.

Here is what the basic aviation regulations say.

Sec. 91.119 -- Minimum safe altitudes: General.
Except when necessary for takeoff or landing, no person may operate an aircraft below the following altitudes:
(a) Anywhere. An altitude allowing, if a power unit fails, an emergency landing without undue hazard to persons or property on the surface.
(b) Over congested areas. Over any congested area of a city, town, or settlement, or over any open air assembly of persons, an altitude of 1,000 feet above the highest obstacle within a horizontal radius of 2,000 feet of the aircraft.

HOWEVER. Since we're talking about a quadcopter, we must continue to read.

(d) Helicopters, powered parachutes, and weight-shift-control aircraft. If the operation is conducted without hazard to persons or property on the surface --
(1) A helicopter may be operated at less than the minimums prescribed in paragraph (b) or (c) of this section, provided each person operating the helicopter complies with any routes or altitudes specifically prescribed for helicopters by the FAA;

Since there are no "routes or altitudes" involved, para (a) becomes the controlling law:

(a) Anywhere. An altitude allowing, if a power unit fails, an emergency landing without undue hazard to persons or property on the surface.

Note that it doesn't say NO hazard. And, of course, the "except for landing and takeoff" clause means that "surface" is appropriate at certain times.

If people didn't care about getting somewhere during a snowstorm, they already wouldn't be driving around in snowstorms. Today, it's either people who don't care that it's snowing or think they can handle it, and who want to go somewhere. (A small minority go out just to do donuts in the parking lots.) Take away the concern about being able to handle it themselves and you'll wind up with MORE people trying to get somewhere during snowstorms and thus more cars on the road when they shouldn't be.

I.e., if I don't have to worry about my ability to navigate through the snow, I have less reason not to go out to get some beers for the next few days of being snow-bound.

Relax. The climate in the north will be "a warmer climate thing" by the time self-driving cars are perfected enough to sell them to the public. Thank God for climate change, huh? Snow and ice will be a problem only the geezers will remember.

I used to live on the side of a hill. When it snowed, to get into my apartment's parking lot you could NOT use brakes in any way. If you did, you broke traction and slid to the bottom of the hill and across a four lane divided highway. If you didn't try to brake, you either made the turn and were successful, or you retained control and could navigate around the block for another try. What you could never do is go uphill -- you'd slide across that divided highway going backwards.

That's probably true. I'm sure that people will come up with all kinds of "hacks" for their AVs. But the problem will mostly come from REMOTE hackability, which not everything is subject to. You first have to have a remote access capability of some sort.

Of course, "convenience" is more important than "security", which is why we get cable boxes that can be controlled from outside your house and cars that can be controlled by hackers that aren't anywhere close to them.

Yep, the convenience factor rules. And you can't firewall the maps function from the control functions as you suggest because the maps are too integral to the control systems. Map data has to be used by the control systems to know when what they think they see with their cameras as a road actually isn't, or to update construction zone info. If a hacker can send map data that says that three of the four lanes of Interstate 5 you are currently on are closed and the construction speed limit is 5 MPH, is that any different than a direct command to pull over and slow down? And imagine when 50% of the traffic on that section of I5 pulls over into the left hand lane and slows down to 5MPH. THAT'S the new "motor sport" we'll get to see.

But large-dollar liability lawsuits will replace the low-value DUI customers. There will never be "no-fault" for liability of autonomous vehicle manufacturers or anyone involved in making or selling or repairing them.

When in the last thousand years has any change to anything resulted in a reduced demand for lawyers?

Less common? No, someone will have to repair all the autonomous vehicles that get rear-ended after they have a sensor failure and they stop unexpectedly as a precautionary measure.

More people going more places because it is no longer a tedious thing to drive to Gramma's house or the country or beach. And more autonomous cars put into "drive around until I call you back" mode because it costs too much to find parking, if you can find it at all. More gas will be needed.

The only "motor sport" I can think of that will be affected by autonomous vehicles is the sport of standing by the side of the road trying to fool the car's sensors into thinking there's a baby in the middle of the road so you can watch the chain reaction/collisions. (And this is truly one of the times where "affected" and "effected" are both correct!)

No other motor sport would include autonomous vehicles. That's why it is a "sport".

No, advertising about cars will not stop or become less common. In fact, more advertising will be used to hype the miraculous safety record of these new-fangled autonomous vehicules and to try to convince people to abandon a perfectly functional manual car in favor of them.

That's not why people throw trash out the window. It's more a case of "if I don't throw it out the window, I'll have to clean out the car later...", and that won't change.

Whizbang storefront signs aren't there to tell you where the store is, it's there to attract casual passersby. Either to get them to say "hey, that store looks interesting", or "hey, I need to stop there". Otherwise all they'd need is a simple sign saying "Joe's Eats" so you know which door to walk in after your car dumps you on the sidewalk.

Worse than that. I thought this was something to do with a catheter camera bringing us mass beheading pictures from a radical Islamic proto-state.

What an idiotic nonsequitor. I didn't claim it wasn't against the law to fly a manned aircraft at head level near people, I responded to your incorrect statement:

According to TFA it was flying well below any level ever though of as "airspace"

You made a patently absurd claim about what is considered "airspace", and I corrected you on it. The fact that some "airspace" extends to the surface (below "head level") doesn't make it legal for everyone to fly anything they want there. IN FACT, the fact that airspace extends to the surface is what gives the FAA the authority to regulate it, and to make flight within certain distances of people or structures illegal.

I'm sorry, but your claim that toy drones fly below any level that anyone ever thought of as airspace is just absurd.

And they apparently lost since I see such labels on products currently for sale.

Ask the grocery. It's their sign. Maybe they don't want to needlessly scare ignorant people?

Because, of course, it makes one single bit of difference in the safety or taste of the product if it is covered by a patent or not. Sure.

What other useless information should be mandated for food labels just because you want to know it? Isn't it good enough that any company that wants to create a market advantage for itself can do so by displaying the patent information? Maybe that's a clue that it isn't really that important to anyone else.

I'm so glad you can tell me what the real argument they were making is, because they said nothing like that at any time. They bandied about phrases like "food justice" and other fictional rights. They said nothing about what people could EAT, only what they could grow or use in their work.

Hmmm. Let's see. Here's a solution to your problem: pass a law that says that nobody can grow or use any GMO product, and that every farmer who is doing so will have 90 days to rip his GMO crops out of the ground without any compensation from anyone for the loss. Who cares if your law forces diabetics to drive to the next county over to get the insulin they need to survive, more people driving more cars on the road is a good thing, right? Who cares if such a law would have nothing to do with how many ingredients your spaghetti sauce has?

Or you could just buy the food you want to eat and let others do the same. Hmmm. Which is a better, more rational way to proceed?