<story><title>Accurate Navigation Without GPS</title><url>https://spectrum.ieee.org/tech-talk/transportation/sensors/accurate-navigation-without-gps</url></story><parent_chain><item><author>DamnInteresting</author><text>Strange that they don&amp;#x27;t use the age-old term for this sort of position-tracking: dead reckoning.&lt;p&gt;&lt;a href=&quot;https:&amp;#x2F;&amp;#x2F;en.wikipedia.org&amp;#x2F;wiki&amp;#x2F;Dead_reckoning&quot; rel=&quot;nofollow&quot;&gt;https:&amp;#x2F;&amp;#x2F;en.wikipedia.org&amp;#x2F;wiki&amp;#x2F;Dead_reckoning&lt;/a&gt;</text></item></parent_chain><comment><author>nabla9</author><text>They use dead reckoning.&lt;p&gt;Dead reckoning requires speed information. They have invented an application specific way to reduce  cumulative errors in speed from IMU unit.&lt;p&gt;Accelerometers and gyroscopes can&amp;#x27;t differentiate between constant linear speed and staying still (both have zero acceleration) and errors in speed accumulate constantly.
Airplances and ships have ways to measure speed  without GPS, even if  currents or wind prevent accurate ground speed measurements. Small inexpensive devices like this don&amp;#x27;t have that.&lt;p&gt;This application uses foot movement to calibrate speed in every step. The same can be done with laser, ultrasound etc. but doing it with IMU sensors only is a neat trick.</text></comment>
<story><title>Accurate Navigation Without GPS</title><url>https://spectrum.ieee.org/tech-talk/transportation/sensors/accurate-navigation-without-gps</url></story><parent_chain><item><author>DamnInteresting</author><text>Strange that they don&amp;#x27;t use the age-old term for this sort of position-tracking: dead reckoning.&lt;p&gt;&lt;a href=&quot;https:&amp;#x2F;&amp;#x2F;en.wikipedia.org&amp;#x2F;wiki&amp;#x2F;Dead_reckoning&quot; rel=&quot;nofollow&quot;&gt;https:&amp;#x2F;&amp;#x2F;en.wikipedia.org&amp;#x2F;wiki&amp;#x2F;Dead_reckoning&lt;/a&gt;</text></item></parent_chain><comment><author>blt</author><text>Dead reckoning is like pure IMU integration. In this work they detect the instant of zero velocity and do something like a Kalman update with a velocity measurement</text></comment>