| Some of TomTom's high-end devices like the TomTom GO 920 have built-in accelerometers and gyros, and use "Enhanced Positioning Technology" to perform augmented dead reckoning when GPS signals are not available, like in tunnels and highly built-up areas. 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. |