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Comment: Re:GPS? (Score 1) 218

by Mike1024 (#33628002) Attached to: Helicopter Crashes While Filming Autonomous Audi

I'm curious about the $100,000 GPS system. They sell GPS add-ons for $70. So what kind of GPS costs $100,000? Military, I suppose.

1. A part of the error on GPS is due to things like radio signals slowing down as they travel through the ionosphere. If you set up a GPS base station at a known location, you can take GPS measurements, work out the errors due to the ionosphere (and similar things), transmit that to the receiver on the car, and subtract the errors there. Within a few kilometres of the base station lots of the errors will be common - so a lot of errors are eliminated. (if you don't want to operate your own base station, there are services like Omnistar which operate a network of them and radio out the corrections, for a few thousand dollars a year subscription). High cost receivers support doing this!

2. The GPS signal is comprised of a digital signal with a wavelength of about 300m (which we can measure accurate to about 3m) and a carrier wave with a wavelength of about 19cm (which we can measure accurate to a few mm) - but the carrier signal is a sine wave, so it has an 'integer ambiguity'; 1,000,000.1 wavelengths looks identical to 1,000,001.1 wavelengths. High cost receivers can perform 'integer ambiguity resolution' to figure out the integer number of wavelengths, allowing high precision positioning.

3. There's an encrypted military GPS signal at a different frequency - but using certain tricks you can receive the encrypted military signal. By combining two sine waves using a trigonometric identity, you can get a 80cm sine wave - which means there are fewer ambiguity options, making ambiguity resolution faster. Consumer receivers don't attempt this because you need to receive two GPS frequencies instead of one, and at both frequencies your receivers need ten times the bandwidth.

4. Once you've got high precision GPS, you can put one receiver at the front of your vehicle and one at the rear, giving you a 'GPS compass' which can tell you which way your vehicle is pointing, even if you aren't moving. Of course, using two receivers means paying for two.

5. GPS measurements can be combined with measurements from an intertial measurement unit (IMU) - a sensor system with gyroscopes and accelerometers which can give fast updates, but which are prone to drift over time (as they're based on integrating acceleration to give speed and accelerating speed to give position, a small acceleration error eventually leads to a big position error). The more you spend on your IMU, the lower the drift rate. GPS measurements aren't prone to this drift, but there can be GPS outages (e.g. when going though tunnels) and GPS receivers don't give measurements as fast as an IMU can, so you combine GPS measurements with IMU measurements, usually using an extended Kalman filter.

6. Radio waves can reflect from trees, buildings, and the ground. This is called 'multipath'. High cost receivers use expensive antennas (like choke ring antennas) which have lower gain at lower elevations - which reduces problems with signals reflected from the ground. These antennas are more expensive to manufacture than consumer receivers.

7. Mobile phone GPS chips are produced by the million. The market for high-precision GPS is very much smaller, so the costs of engineering all the above have to be recouped over fewer units - so the equipment is expensive.

In summary, when you spend $100,000 on a GPS system you get a base station and radio link, two rover receivers, all the receivers are capable of receiving the military signal, you get special software that can perform ambiguity resolution for centimetre-precise positioning, you get three high quality antennas, and you get a high-precision IMU and software to go with it.

A lot of this technology could probably be made a lot cheaper if it were mass-produced and installed on every car, as a lot of it's in electronics and software. But in the world of robotics there are a great many sensors that cost $100,000 but could be made a lot cheaper if someone wanted to order a million of them.

If you're interested in autonomous vehicle technology, I advise you to check out The Great Robot Race - it's a good documentary.

Even if they could make the GPS more cheaply, wouldn't this imply that they expect the very accurate military-grade GPS service to be available to consumers in future? Galileo was abandoned, wasn't it?

Right now, if you're a farmer, you can buy a GPS autopilot system with high-precision GPS receivers which will link into your tractor's power-assisted steering and guide your tractor down crop rows with centimetre-level precision. Off the shelf, for maybe $40,000.

Galileo's still going - used together with GPS, high precision GPS will become simpler and more reliable.

Comment: Re:Technology / Hacking Laws (Score 3, Insightful) 432

by Mike1024 (#33172980) Attached to: Ex-SF Admin Terry Childs Gets 4-Year Sentence

I know this sounds very arrogant, but I would love to see trials change so you're actually judged by your peers instead of members of the public, so for example doctors by doctors, network admin by other network admin, and such. That way you can get a bunch of people who know how far this person has stepped out of line.

Wouldn't that create the situation where professional communities could just decide for themselves what the law was?

BP's CEO has broken pollution laws? Not according to a jury of oil company CEOs!

Comment: Re:News on the BBC is not free (if you live in UK) (Score 1) 246

by Mike1024 (#31352562) Attached to: BBC To Make Deep Cuts In Internet Services

However, it's actually pretty difficult to convince the authorities that you don't watch or record live TV. You're in for a world of harassment if you don't have a TV licence.

Not true for me the three times in the past five years that I've moved house. Simply telephone the number on the 'reminder' letters they send you, tell them you do not have a TV, and letters stop arriving.

Hardly a world of harassment.

Comment: Re:Well, telling them doesn't work (Score 1) 243

by Mike1024 (#30794216) Attached to: Protecting At-Risk Cities From Rising Seas

Even though they are clearly marked on the maps, and (presumably) are discovered in property searches, people still buy these places. [...] they whine and moan about "our house has flooded ... you gotta HELP us!" [...] All I would suggest is huge .... massive .... crippling ... increases in home insurance premiums to both alert buyers to the dangers and also to make them pay the going rate for repairs and renovations

I see your point, but:

Imagine I was a hard-working person, I'd been saving up for a few years, and after learning my wife was pregnant we'd brought a house for £170,000 so we'd have the space we needed. Put down a £30,000 deposit on it - all my life's savings. I've been fully responsible, done every calculation there is to be done, I've brought a house with a price within my means, I've checked what the insurance costs are going to be.

The next day, the government announces "from now on there will be no flood assistance for anyone" and insurers decide to levy huge, massive, crippling increases in home insurance premiums.

So now I can't afford my insurance payments - maybe I should move, right? Well I'd like to, but it turns out my £170,000 house is now only worth £100,000 - so even if I sell it, I'd still be £40,000 in debt, and I'd have no money for a deposit on a new house.

Is that a desirable outcome? Will it be good for the economy? Would it be good for the re-election prospects of the politicians who introduced it?

I'm not saying I disagree with you entirely - just that I wouldn't hold your breath waiting for anything to happen.

Comment: Re:Misses part of the point (Score 1) 849

by Mike1024 (#30141194) Attached to: Can We Really Tell Lossless From MP3?

Yeah, I don't know why people don't understand this. Sure, AAC and MP3 are the hot lossy formats *today*, but will they be so hot 10 years from now?

I see a few posts saying this, but doesn't it seem a bit odd to say "The benefit of FLAC over MP3 is that you can convert FLAC to MP3 and it will sound no worse than the direct-to-MP3 conversion"?

The argument that FLAC is useful because you might want to convert to a different lossy format later on relies on certain assumptions; (a) that a format will turn up that's sufficiently better than MP3 that people will want to convert from MP3. And given that this study states that people can't tell MP3 from FLAC I'm not sure what such a format would have to offer (perhaps smaller file sizes, but with the ever-reducing cost of flash memory and hard disk space I'd be surprised if this warranted a changeover) or (b) that if MP3 should become obsolete or unsupported by players, FLAC will remain well enough supported for you to transfer from... even though FLAC has orders of magnitude fewer users than MP3.

Comment: Re:Oh great (Score 1) 57

by Mike1024 (#30070364) Attached to: Making Carriers Shoulder Smartphone Security

So they are going to deploy the ability to remotely update the users device. Because the bad guys will never figure out how the company does it. I can see it now. An entire carriers smart cell line bricked by a remote exploit that updates phones.

People often say things like this here on Slashdot, but automatic update tools like Debian's apt-get and Microsoft's Windows Update have never been hacked and used to distribute virus-ridden updates*. My Ubuntu netbook has never been "bricked by a remote exploit" even though it's open source, so be bad guys know exactly how the update mechanism works.

In other words, we have the technology to make secure remote update software. Technology like public/private key cryptography to digitally sign updates, and only apply those with a valid, trusted signature.

What makes you think remote updates for cell phones would be any less secure?

*Unless you count [WGA / .NET / Ubuntu 9.10 (delete as appropriate)]. Rimshot!

Comment: Re:problems with complexity (Score 1) 1146

by Mike1024 (#29975630) Attached to: Toyotas Suddenly Accelerate; Owners Up In Arms

Premium class automobile - ~ 100 million

Maybe - but how many of those lines of code do you suppose are capable of causing unintended acceleration?

Every car I'm aware of has different wires and connections for different types of traffic - so the in-car DVD entertainment system is on a different system to the electric wing mirror adjustment and keyless entry and electronic boot entry and electronic climate control, which is on a different system to the throttle, which is on a different system to the cruise control and ABS. And the foot brake is still connected by a conventional hydraulic system.

The purpose of this separation is because of the point you're making - it may not be practical to prove 100 million lines of code is bug-free, but what you can do is perform a lot of testing on the ~1000 line throttle-by-wire system, including testing for all of the (small number of) inputs it can get from elsewhere in the vehicle.

My point being: It's bogus to say "Throttle-by-wire must be unsafe because cars have 100 million lines of code which is more than can be validated" because most of those lines of code, by design, are isolated from the safety-critical systems, and the safety critical systems are small enough that they can believably be validated.

Comment: Re:One thing and another (Score 1) 279

by Mike1024 (#29766407) Attached to: MS Says All Sidekick Data Recovered, But Damage Done

What we see here is a small device storing it's data remotely and I wonder why.
Considering how cheap a couple of GB of memory are and how precious wireless bandwidth is this can mean only one thing, having and thus exploiting that data is worth more than the cost of the bandwidth.

There could be other reasons - despite the obvious backup failure in this story, I'd imagine sidekick users who lose their phones appreciate not losing their data along with it.

Additionally, if someone with important information on their device were to lose their device, I can see how you might prefer it if it didn't come with an SD card full of confidential documents and e-mails. Sure, it would be nice if you could get users to use encryption on their devices, but I only know one person who uses the 'security pin' feature of their smartphone, and even he only has a 4-numeric-digit PIN set; users haven't accepted strong passwords on their smartphones, and remote wipe is the second-best thing.

I mean, from the perspective of the enterprise market that BlackBerry etc serve, those would seem like pretty useful features to me.

Mozilla

Firefox 3.6 Alpha 1 Released 212

Posted by timothy
from the waiting-in-the-wings dept.
An anonymous reader writes with word of the release of the first alpha of Firefox 3.6, "intended for developers and testers only." "As with Firefox 3.5, there are improvements to the performance; pages render faster, and pages with JavaScript code run much faster with the new Tracemonkey engine. Although this Firefox version carries the code name 'Namoroka' Alpha 1, it is also currently referred to as Firefox.next. And like other Firefox Alphas, it does not bear the Firefox logo. This release uses the Gecko 1.9.2 engine and will likely include several interface improvements in later versions, such as new graphical tab-switching behavior, which was removed from 3.5 with Beta 2." Update: 08/09 03:54 GMT by T : Read more at InaTux.com.

Comment: Re:Then open it up (Score 1) 176

by Mike1024 (#28767533) Attached to: Valve's Newell On Community-Funded Games

I think that what Gabe suggests is quite reasonable, to say the least. People do pay for games right now, [...] Think of it as an early preorder method.

I agree that it could work in principle - but the summary talks about "publishers who are very shy about investing in new projects, particularly for unproven IPs" and "Such a system would certainly relieve some of the pressure to stick with tried-and-true concepts"; would it actually accomplish that?

I mean, sure, I'd pre-order "Half Life 2 Episode 3" because I know I'm going to buy it anyway - but how would you get financing from fans when a "new unproven IP" by definition doesn't yet have any fans?

Some people might be willing to invest in a game that didn't yet exist on the strength of the studio or people involved (John Romero!), or simply on the basis of a written description and some concept art, but that would represent a much higher risk investment than waiting for the game to come out and reading reviews of it.

Comment: Re:Anyone know the economics on these? (Score 1) 462

by Mike1024 (#28585659) Attached to: New Video of Tesla's Mass-Market Electric Car

I imagine a good electric vehicle being had for less than 2000 dollars, and being a 3-wheel, 2 seater with a lightweight basket capable of carrying a couple bags of groceries. It would have to be weather-proof, but that could (and should) be accomplished using something cheap and effective like tarp and plexi-glass and aluminium.

Sounds a lot like an electric rickshaw.

Seriously, though, there are already lots of more efficient car alternatives, people in the US just don't choose to use them, due to a combination of infrastructure, social, and capability limitations.

If people aren't giving up their cars (in appreciable numbers) for busses, trains, pushbikes, motorbikes, motortrikes, motor scooters, enclosed scooters, electric bikes, european 'city cars', community cars, or car sharing.

What would an electric rickshaw offer that would cause it to be more successful than those?

Comment: Re:Speed Interlock Override (Score 2, Insightful) 225

by Mike1024 (#28435611) Attached to: Watch TV On Your Satnav

Even the current GPS units/DVD players can easily be defeated. In most cases, all you need to do is ground one of the pins in the connector, and it always thinks you are parked.

I've heard some people who want a GPS/DVD player with the GPS functions disabled take the even more nefarious route of just buying a DVD player :-)

"Why should we subsidize intellectual curiosity?" -Ronald Reagan

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