<story><title>MIT Turns Wi-Fi into Indoor GPS</title><url>http://spectrum.ieee.org/tech-talk/telecom/wireless/mit-turns-wifi-into-indoor-gps</url></story><parent_chain></parent_chain><comment><author>fennecfoxen</author><text>&amp;gt; Although Chronos can run on existing Wi-Fi devices using just an app (or a firmware upgrade for an access point), each device has to undergo a one-time distance calibration.&lt;p&gt;I worked at at an indoor location-systems startup once. 
The real fun part of the system was integrating wifi-based location with streaming video from fixed-mount cameras to pinpoint location even better. But let me tell your right off: wifi calibration of the sort they&amp;#x27;re talking about can be incredibly obnoxious (think &amp;quot;carefully rolling a laptop in a cart at a constant speed around a space, in a grid&amp;quot;, which could easily be completed in an hour or two if you are really good at it, but might take a day or two to get right if you aren&amp;#x27;t.) Sure, this is all fine if you want to calibrate one or two indoor spaces for your automated drones, especially if  you&amp;#x27;ve already got APs deployed in a location-friendly mode (i.e. more around the perimeter and less around the center, with antenna orientation to match), but don&amp;#x27;t expect to see it in a corner store near you anytime soon.&lt;p&gt;Now, if you can talk about automating the calibration you&amp;#x27;ll do quite well.</text></comment>
<story><title>MIT Turns Wi-Fi into Indoor GPS</title><url>http://spectrum.ieee.org/tech-talk/telecom/wireless/mit-turns-wifi-into-indoor-gps</url></story><parent_chain></parent_chain><comment><author>jdiez17</author><text>Very cool. They are using Time Difference of Arrival analysis[1], the fact that most devices have two or more antennas, and clever software to get 10-80 cm accuracy at a good enough frequency to be used as a positional reference in a quadcopter, see the paper[2] for more info&lt;p&gt;Existing indoor positioning systems such as Bluetooth LE beacons and WiFi triangulation[3] only use the RSSI value and trigonometry to figure out the position. This method is slow (5Hz or so) and the resolution of the RSSI is bad unless you sample it directly, eg with SDR (which incidentally, is what my dissertation is about!)&lt;p&gt;[1] &lt;a href=&quot;https:&amp;#x2F;&amp;#x2F;en.wikipedia.org&amp;#x2F;wiki&amp;#x2F;Multilateration#Principle&quot; rel=&quot;nofollow&quot;&gt;https:&amp;#x2F;&amp;#x2F;en.wikipedia.org&amp;#x2F;wiki&amp;#x2F;Multilateration#Principle&lt;/a&gt;&lt;p&gt;[2] &lt;a href=&quot;https:&amp;#x2F;&amp;#x2F;www.usenix.org&amp;#x2F;system&amp;#x2F;files&amp;#x2F;conference&amp;#x2F;nsdi16&amp;#x2F;nsdi16-paper-vasisht.pdf&quot; rel=&quot;nofollow&quot;&gt;https:&amp;#x2F;&amp;#x2F;www.usenix.org&amp;#x2F;system&amp;#x2F;files&amp;#x2F;conference&amp;#x2F;nsdi16&amp;#x2F;nsdi16...&lt;/a&gt;&lt;p&gt;[3] &lt;a href=&quot;https:&amp;#x2F;&amp;#x2F;www.qualcomm.com&amp;#x2F;products&amp;#x2F;izat&quot; rel=&quot;nofollow&quot;&gt;https:&amp;#x2F;&amp;#x2F;www.qualcomm.com&amp;#x2F;products&amp;#x2F;izat&lt;/a&gt; (unfortunately there are no public &amp;#x27;specs&amp;#x27; I can find...)</text></comment>