Interesting to read about alternative, non-centralized, forms of navigation. I wish modern cars which already have all the necessary sensors would use this method as a fallback, since GPS reception is not always available.
What does "old" have to do with it? Modern code is all like that too. Every time I complain about it, including just a day or two right here on HN, I get a bunch of responses saying "I don't need comments, my code is self-documenting". In my experience, most programmers do not use comments much at all, and it's entirely incomprehensible to anyone new to the project.
You seem to be thinking of cell tower triangulation, not GPS. I do agree that GPS also does not do particularly well in areas with large buildings: it needs a clear view of the sky which can be hard to come by when there's skyscrapers everywhere.
Instead, you use A-GPS, which is GPS with additionally communication with a server for accuracy.
Dead reckoning using just acceleration data loses accuracy quickly. Using turns to reset position is a really good idea. I think I've seen my iPhone do a similar "recovery" procedure when it gets a little off track.
http://corporate.tomtom.com/releasedetail.cfm?releaseid=3185...
Best navigation with Enhanced Positioning Technology
TomTom’s new Enhanced Positioning Technology uses movement and gravity sensors to calculate drivers’ positions when GPS signals are unavailable.
TomTom GO 920 T users will have a much more continuous navigation experience as the Enhanced Positioning Technology ensures the device continues to navigate to its destination, even in circumstances where there may not be a direct line-of-sight connection to a satellite. For example, when driving in a city with tall buildings, underpasses or bridges.
http://www.pocketgpsworld.com/tomtom-go-930-review-a1042.php
As you drive along you will often encounter places where the Satellite signal is blocked such as tunnels and underground parking lots. TomTom has introduced a system called EPT (Enhanced Position Technology) to keep track of your position using accelerometers. This is not as accurate as GPS but will help guide you in places like Boston where the Big Dig has created a network of underground roads.
https://en.wikipedia.org/wiki/TomTom#Enhanced_Positioning
2008: Enhanced Positioning
TomTom released the GO x30 range in April 2008 based on NavCore 8. New features included IQ Routes, which estimated journey times based on average recorded speeds, rather than speed limits, and Advanced Lane Guidance, an on-screen representation of the correct lane to take. The 930, like the x20, had Enhanced Positioning Technology. GSM HD Traffic receivers, plugging into the car's cigarette lighter, added HD Traffic to the GO range.
Refreshed ONE and XL models were released in May 2008, still based on NavCore 7, with an improved speaker.
NavCore 8 updates for NavCore 7 devices, including the ONE v3 and v4, were released in June 2008, giving x20 users (only) IQ Routes and Advanced Lane Guidance, with the purchase of new maps.
This happens too often for benign reasons (and GPS hacking too rare) for it to be useful. The GPS system in my Ford Focus jumps around wildly if I start the car in an enclosed space before it gets a good lock, and it can be thrown-off under bridges and around tall buildings as it doesn't have A-GPS (does any car have A-GPS?). The worst is when a poor signal is combined with road-snapping - I've had a lot of trouble with off-ramps on partially submerged urban highways, the I-5 in downtown Seattle, for example.