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NemeriX and Bosch Sensortech Enhance Vertical GPS Accuracy


Through a partnership between NemeriX and Bosch Sensortech, a new GPS chipset is being developed which will significantly enhance vertical accuracy. Typically, the accuracy of GPS isn’t quite as accurate in the vertical axis as it is horizontally. But what difference does that make for automotive GPS devices? Most often, it doesn’t. If the GPS is only accurate to 100 vertical feet it will still know where you are on the road. However there are times when you might want a greater degree of vertical accuracy.

More and more cities are creating “stacked” road systems where one highway runs up and above another highway on a long bridge. In this case despite having sub-meter horizontal accuracy, the GPS might misinterpret your height and get confused about what road you are traveling on. A similar situation can develop if you are on a surface road while there is a tunnel underneath you. This could lead to navigation errors if the device gives you turn instructions for one road while you are on a different road.

This new technology works by combining the information received from the GPS satellites with barometric pressure information derived by the new chipset. I’ve used lots of devices in the past which offer standalone altimeters, or GPS with altitude information augmented by barometric pressure. The one downside to those devices is that they often rely on recalibration of the internal barometric sensor with local weather changes. So we asked about how this might be different and if users will need to calibrate their devices. Here is what we were told.

This technique does not rely on user to adjust the barometric pressure. The natural changes in weather are automatically compensated by permanent calibration against GPS, even in case of significant vertical dynamics (in clear, we do not impose that the user stays static during the calibration phase). Of course, a prolonged scenario with GPS unavailable (let’s say beyond ½ to 1 hour) would prevent continuous calibration, and the vertical accuracy could progressively degrade (in case of changing weather conditions). This expected degradation would be reported to the user (or to the application) to ensure that the user knew this.

So it seems like they have figured out how to avoid the user needing to adjust the barometric sensor. If you live out in rural areas where the road elevation is always at ground level, you might not get as much appreciation out of this technology. But for those people who live in areas of stacked roads and tunnels, looking out for devices which offer this chipset in the future could provide relive to a big GPS headache.

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