Editing Dead reckoning (section)

=={{anchor|PDR|UDR}}Pedestrian dead reckoning==
With the increased sensor offering in [[smartphone]]s, built-in accelerometers can be used as a [[pedometer]] and built-in [[magnetometer]] as a compass heading provider. '''Pedestrian dead reckoning''' ('''PDR''') can be used to supplement other navigation methods in a similar way to automotive navigation, or to extend navigation into areas where other navigation systems are unavailable.<ref>{{cite AV media|title=Pedestrian Dead Reckoning (PDR) Simplified|url=https://www.youtube.com/watch?v=IQt5-LfqeZw| archive-url=https://ghostarchive.org/varchive/youtube/20211211/IQt5-LfqeZw| archive-date=11 December 2021 | url-status=live|publisher=GT Silicon|access-date=22 January 2018}}{{cbignore}}</ref>

In a simple implementation, the user holds their phone in front of them and each step causes position to move forward a fixed distance in the direction measured by the compass. Accuracy is limited by the sensor precision, magnetic disturbances inside structures, and unknown variables such as carrying position and stride length. Another challenge is differentiating walking from running, and recognizing movements like bicycling, climbing stairs, or riding an elevator.

Before phone-based systems existed, many custom PDR systems existed. While a [[pedometer]] can only be used to measure linear distance traveled, PDR systems have an embedded magnetometer for heading measurement. Custom PDR systems can take many forms including special boots, belts, and watches, where the variability of carrying position has been minimized to better utilize magnetometer heading. True dead reckoning is fairly complicated, as it is not only important to minimize basic drift, but also to handle different carrying scenarios and movements, as well as hardware differences across phone models.<ref>{{Cite journal|last1=Yu|first1=N.|last2=Zhan|first2=X.|last3=Zhao|first3=S.|last4=Wu|first4=Y.|last5=Feng|first5=R.|date=February 2018|title=A Precise Dead Reckoning Algorithm Based on Bluetooth and Multiple Sensors|url=https://ieeexplore.ieee.org/document/8219408|journal=IEEE Internet of Things Journal|volume=5|issue=1|pages=336–351|doi=10.1109/JIOT.2017.2784386|s2cid=46857039 |issn=2327-4662}}</ref>