{"status":"ok","message-type":"work","message-version":"1.0.0","message":{"indexed":{"date-parts":[[2025,10,11]],"date-time":"2025-10-11T21:17:27Z","timestamp":1760217447762,"version":"build-2065373602"},"reference-count":28,"publisher":"MDPI AG","issue":"9","license":[{"start":{"date-parts":[[2015,8,28]],"date-time":"2015-08-28T00:00:00Z","timestamp":1440720000000},"content-version":"vor","delay-in-days":0,"URL":"https:\/\/creativecommons.org\/licenses\/by\/4.0\/"}],"content-domain":{"domain":[],"crossmark-restriction":false},"short-container-title":["Sensors"],"abstract":"<jats:p>This paper introduces a framework for inferring human activities in mobile devices by computing spatial contexts, temporal contexts, spatiotemporal contexts, and user contexts. A spatial context is a significant location that is defined as a geofence, which can be a node associated with a circle, or a polygon; a temporal context contains  time-related information that can be e.g., a local time tag, a time difference between geographical locations, or a timespan; a spatiotemporal context is defined as a dwelling length at a particular spatial context; and a user context includes user-related information that can be the user\u2019s mobility contexts, environmental contexts, psychological contexts or social contexts. Using the measurements of the built-in sensors and radio signals in mobile devices, we can snapshot a contextual tuple for every second including aforementioned contexts. Giving a contextual tuple, the framework evaluates the posteriori probability of each candidate activity in real-time using a Na\u00efve Bayes classifier. A large dataset containing 710,436 contextual tuples has been recorded for one week from an experiment carried out at Texas A&amp;M University Corpus Christi with three participants. The test results demonstrate that the multi-context solution significantly outperforms the  spatial-context-only solution. A classification accuracy of 61.7% is achieved for the spatial-context-only solution, while 88.8% is achieved for the multi-context solution.<\/jats:p>","DOI":"10.3390\/s150921219","type":"journal-article","created":{"date-parts":[[2015,9,1]],"date-time":"2015-09-01T10:55:58Z","timestamp":1441104958000},"page":"21219-21238","update-policy":"https:\/\/doi.org\/10.3390\/mdpi_crossmark_policy","source":"Crossref","is-referenced-by-count":15,"title":["Inferring Human Activity in Mobile Devices by Computing Multiple Contexts"],"prefix":"10.3390","volume":"15","author":[{"given":"Ruizhi","family":"Chen","sequence":"first","affiliation":[{"name":"Conrad Blucher Institute for Surveying & Science, Texas A&M University Corpus Christi,  Corpus Christi, TX 78412-5868, USA"}],"role":[{"role":"author","vocabulary":"crossref"}]},{"given":"Tianxing","family":"Chu","sequence":"additional","affiliation":[{"name":"Conrad Blucher Institute for Surveying & Science, Texas A&M University Corpus Christi,  Corpus Christi, TX 78412-5868, USA"}],"role":[{"role":"author","vocabulary":"crossref"}]},{"given":"Keqiang","family":"Liu","sequence":"additional","affiliation":[{"name":"Conrad Blucher Institute for Surveying & Science, Texas A&M University Corpus Christi,  Corpus Christi, TX 78412-5868, USA"},{"name":"School of Environment Science and Spatial Informatics, China University of Mining and Technology, Xuzhou 221116, China"}],"role":[{"role":"author","vocabulary":"crossref"}]},{"given":"Jingbin","family":"Liu","sequence":"additional","affiliation":[{"name":"Department of Remote Sensing and Photogrammetry, Finnish Geospatial Research Institute, National Land Survey of Finland, Masala 02431, Finland"}],"role":[{"role":"author","vocabulary":"crossref"}]},{"ORCID":"https:\/\/orcid.org\/0000-0003-0148-3609","authenticated-orcid":false,"given":"Yuwei","family":"Chen","sequence":"additional","affiliation":[{"name":"Department of Remote Sensing and Photogrammetry, Finnish Geospatial Research Institute, National Land Survey of Finland, Masala 02431, Finland"}],"role":[{"role":"author","vocabulary":"crossref"}]}],"member":"1968","published-online":{"date-parts":[[2015,8,28]]},"reference":[{"key":"ref_1","unstructured":"Google Now. 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