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. 2021 Jan 13;9(1):e19609. doi: 10.2196/19609

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©Mamoun T Mardini, Subhash Nerella, Matin Kheirkhahan, Sanjay Ranka, Roger B Fillingim, Yujie Hu, Duane B Corbett, Erta Cenko, Eric Weber, Parisa Rashidi, Todd M Manini. Originally published in JMIR mHealth and uHealth (http://mhealth.jmir.org), 13.01.2021.

This is an open-access article distributed under the terms of the Creative Commons Attribution License (https://creativecommons.org/licenses/by/4.0/), which permits unrestricted use, distribution, and reproduction in any medium, provided the original work, first published in JMIR mHealth and uHealth, is properly cited. The complete bibliographic information, a link to the original publication on http://mhealth.jmir.org/, as well as this copyright and license information must be included.

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An illustration of the ellipse encompassing all the GPS coordinates for a participant during a 1-day time frame. The dashed line passing through the center represents the ellipse minor axis, and the solid line passing through the center represents the ellipse major axis.