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Dead reckoning fills-in GPS navigation gap

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Carlos1966
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re: Dead reckoning fills-in GPS navigation gap
Carlos1966   9/7/2011 3:31:48 PM
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Duane, Typically the Kalman Filter as used in an inertial navigation system is estimating the drift and bias of the gyros and accelerometers along with other modeled errors in the system. These values are what is being calibrated. The calibrated values are then used to correct the estimates made by integrating the accelerations.

Duane Benson
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re: Dead reckoning fills-in GPS navigation gap
Duane Benson   8/26/2011 5:29:18 PM
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It's not clear if the "constant calibration" is just positional calibration so that the nav system will know the last known good location, or if it is also calibrating for vehicle variables, such as tire size. If the vehicle ends up with different size tires or after enough wear, the odometer / wheel sensors will not be giving accurate distance measurements. If the nav system is constantly reading those sensors and calculating the actual verses sensed speed and distance, the accuracy would be greater under a variety of real-world conditions.

kmilnes
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re: Dead reckoning fills-in GPS navigation gap
kmilnes   8/25/2011 6:30:45 PM
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Technology gets reinvented many times. In 1985 a Silicon Valley company, Etak, pioneered the consumer vehicle navigation technology. They invented and marketed a system that used differential wheel sensors, magnetic compass, and map matching for navigation. Maps were stored on a cassette tape, heading was measured with a flux gate compass, and distance traveled was measured by a variable reluctance sensor mounted next to magnetic tape stuck to the inside of the wheel rim. The two non-driven wheels were instrumented so that relative turns could be measured. Maps were displayed on a CRT using vector graphics. Several key patents were issued to them including map matching, absolute and relative heaing sensor fusion, heading up map display, and methods to label the streets. The popular vehicle navigation systems of today have their roots in the Etak Navigator. The system suffered from the lack of an absolute position sensor (i.e. GPS). It would be another 15 years until GPS became economical. It did work remarkably well for the limited sensors available. It would typically navigate without "getting lost" for about 200 miles in both urban and rural environments. Etak went through several mergers and acquisition (News Corp, Sony, TeleAtlas and now TomTom).

docdivakar
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re: Dead reckoning fills-in GPS navigation gap
docdivakar   8/24/2011 11:47:57 PM
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Agree! If it were up to marketing types, we would have ridiculous words & phrases that may not have anything to do with the product. In my dictionary, an alternate for 'ded'uced reckoning would be 'common sense!' It surprising how fast people let go of it these days, getting addicted to GPS's & mobile phones. Unlike most places in Asia, cities in USA are laid out in grid iron pattern and are quite easy to navigate without 'artificial' aides! Try doing that in a rural town in China or India, you will need the 'positioning' advice of a number of locals before you get your distination! MP Divakar

c.scott
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re: Dead reckoning fills-in GPS navigation gap
c.scott   8/24/2011 7:09:43 PM
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Which is why I'm glad marketing people aren't in charge of (re)naming things all the time... Taking 30 seconds to look up the name meaning came up with this: dead reckoning - a homophone of ded (for deduced) reckoning.

selinz
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re: Dead reckoning fills-in GPS navigation gap
selinz   8/24/2011 6:52:27 PM
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Seems like it's a bad marketing idea to use the term dead...

tomkawal1
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re: Dead reckoning fills-in GPS navigation gap
tomkawal1   8/24/2011 3:01:22 PM
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It's been for a while - all the gyros and odometer. If thinking seriously about autonomous driving, for increased safety, one need to provide network of transponders along motorways and process the signal similar way satellites are used. There are some technical issues, like precise timing of the network == huge cost, but balanced by better efficiency.

David Ashton
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re: Dead reckoning fills-in GPS navigation gap
David Ashton   8/21/2011 10:53:08 PM
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"...typical signal strength....of 120 dBm (1 x 1015W)." Shouldn't this be -120 dBm? 120dBm would be 1 x 10+9 watts - a gigawatt.... Nevertheless a great article. My GPS gets totally confused in Sydney's urban canyons (and so do I if I am going somewhere I am not familiar with). I'd thought about accelerometers myself to help the GPS. As Erebus says, the old fasioned Map is also a good solution. I keep a Sydney CBD map in my glove box for these occasions.

EREBUS0
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re: Dead reckoning fills-in GPS navigation gap
EREBUS0   8/21/2011 9:45:09 PM
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Dead reckoning has been used for millenia for navigation the world wide. It is amazing to me how quickly people forget that we found places just fine with maps and street signs long before GPS became readily available. Vehicles with installed inertial navigation systems and digital maps should be more than sufficient to augment the GPS driven navigation needed today. That said, I cannot overstress the need for driver participation in the process. If you put all of your reliance on the computers, it will not end well. Thanks,

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