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Comment iPhone 3G/3GS GPS bug (Score 5, Interesting) 275

Since we're talking about phone bugs, here's one I had to fight with for a while...

Lots of users are having problems with the GPS functionality on the iPhone 3G/3GS (see e.g. here). No apparent pattern there, but in Brazil, lots of users from one specific carrier were having GPS problems, and the beginning of these problems coincided with the start of Daylight Savings Time in Brazil. My iPhone, as well as my girlfriend's, are with this carrier and were experiencing the problem. Those with unlocked phones report trying other carriers' SIM cards and had GPS working again, but once you popped back the problematic carrier's SIM card, the GPS was dead again.

This nearly drove me nuts as I paid an obscene amount of money for the TomTom app and couldn't get it to work, so keeping up with the engineer spirit, I tried to debug the problem myself. I observed an interesting fact: there's a Clock app on the iPhone with a World Clock pane, and if I added a clock from any time zone, including my own, it was off by one hour. However the iPhone's main clock, shown on the top of the screen, was showing the right time. Eventually I discovered that if I restored my phone as a brand new phone (not restoring from backup) the GPS would work fine and world clocks would be fine... until you reboot the phone. After rebooting, the GPS is gone again and the world clock is off by one hour again.

Now you might ask what the time has to do with GPS. A lot, it turns out. GPS works by triangulating your distance from the satellites in the GPS constellation, which depends on knowing the exact position of the satellites. Since their orbits are corrected every so often, you must rely on so-called ephemeris data from each satellite, which is the required information to compute fairly exact orbits, and is updated fairly often (Wikipedia says GPS receivers should update ephemeris data every 4 hours). Originally this data is broadcast by the satellites themselves in their navigation message, at an awfully slow rate of 50 bits/s. You read it right, bits, not bytes or KB or MB, that's bits. As the navigation message is 1500 bits long, it takes at least 30 seconds to download it, which is about the time most standalone GPS receivers take to get a fix from a cold start (i.e. with stale ephemeris data). To work around this delay, most phones with GPS use the assisted-GPS variety, which downloads ephemeris data from a faster channel such as the cellular network. My theory is that some WTF-worthy excuse for an engineer at the carrier decided that, rather than doing time zone updates the right way, by updating configuration files to point to the new time zone, he'd just rather adjust the clock forward by one hour. The GPS chipset probably works with time zone neutral clocks so it asks for (say) UTC time and gets it off by one hour, and then computes the satellite orbits as though it were one hour later than it actually is. Obviously this means the triangulation computations go horribly wrong and rather than reporting something absurd, the chipset just pretends it couldn't get a fix.

It took a lot of complaining from a lot of people (to the carrier and to the government agencies responsible for telecommunications), but the carrier finally fixed the problem. However, it was a nightmare trying to deal with clueless customer support representatives who didn't try in the least to help (and probably were thinking all along `what does this wacko think GPS has to do with DST?'), just blindly suggesting that we restore the phone, or even try to uninstall the built-in Maps app, or blaming it on Apple and saying they weren't responsible -- and never mind that unlocked phones with SIM cards from other carriers worked fine, and that the iPhone support situation is unique in Brazil as Apple outsourced support to the carriers themselves. In the end, the customer support WTFs would be worth another post of its own, at least twice the size of this one.

But my faith in humanity is restored as someone, somewhere within the carrier, actually listened to these detailed explanations of the problem and how to fix it, and actually acted on it. I honestly thought it would take a class action lawsuit to fix it.

The Courts

Four Google Officials Facing Charges In Italy For Errant Video 153

mikesd81 writes to tell us that four Google employees may be facing charges of defamation and failure to control personal data simply because they didn't remove a video of a boy with Down's Syndrome being harassed and eventually hit over the head with a box of tissue, from Google Video. The video was posted in September of 2006 and was removed by Google within a day of receiving the initial complaints, but apparently that isn't fast enough. "Google maintains charges against the employees are unwarranted, Pancini said. Europe's E-commerce Directive exempts service providers from prescreening content before it is publicly posted, he said. Also, the video was technically uploaded to a Google server in the US, not in Italy, Pancini said. 'It was a terrible video,' Pancini said, adding that Google is concerned about the case's impact on censorship on the Internet. The defendants include David C. Drummond, a Google senior vice president, corporate development and chief legal officer. Pancini said Drummond did paperwork to create Google Italy, but has never lived in the country."
The Almighty Buck

Fuel Efficiency and Slow Driving? 1114

vile8 writes "With the high gas prices and ongoing gas gouging in my hometown many people are trying to find a reasonable way to save gas. One of the things I've noticed is people driving exceptionally slow, 30mph in 45mph zones, etc. So I had to take a quick look and find out if driving slow is helpful in getting better mileage. I know horsepower increases substantially with wind resistance, but with charts like this one from it appears mileage is actually about the same between 27mph and 58mph or so. So I'm curious what all the drivers out there with the cool efficiency computers are getting ... of specific interest would be the hemis with MDS; how do those do with the cylinder shutoff mode at different speeds?" Related: are there any practical hypermiling techniques that you've found for people not ready to purchase a new car, nor give up driving generally?

Submission + - Legal Battle For AACS Begins

henrypijames writes: As widely expected, the MPAA has learned nothing from the debacle of its failed prosecution against DVD Jon (of DeCSS) and is now releasing its army of lawyers to fight against the circumvention of AACS (the successor of CSS): Upon the reception of a DMCA takedown notice, SourceForge has immediately terminated its hosting of BackupHDDVD (a tool to backup HD DVD movies, as its suggestes). The project leader is seeking advice on how to proceed.

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