{"status":"ok","message-type":"work","message-version":"1.0.0","message":{"indexed":{"date-parts":[[2025,11,4]],"date-time":"2025-11-04T10:36:16Z","timestamp":1762252576573,"version":"build-2065373602"},"reference-count":56,"publisher":"MDPI AG","issue":"8","license":[{"start":{"date-parts":[[2017,8,4]],"date-time":"2017-08-04T00:00:00Z","timestamp":1501804800000},"content-version":"vor","delay-in-days":0,"URL":"https:\/\/creativecommons.org\/licenses\/by\/4.0\/"}],"funder":[{"name":"the National Science Foundation of China","award":["41301511","41371377","91546106","41371420"],"award-info":[{"award-number":["41301511","41371377","91546106","41371420"]}]},{"name":"National Key Research Development Program of China","award":["2016YFB0502203"],"award-info":[{"award-number":["2016YFB0502203"]}]},{"name":"Nature Science Funding of Shenzhen University","award":["2016064"],"award-info":[{"award-number":["2016064"]}]}],"content-domain":{"domain":[],"crossmark-restriction":false},"short-container-title":["Sensors"],"abstract":"<jats:p>Localization of users in indoor spaces is a common issue in many applications. Among various technologies, a Wi-Fi fingerprinting based localization solution has attracted much attention, since it can be easily deployed using the existing off-the-shelf mobile devices and wireless networks. However, the collection of the Wi-Fi radio map is quite labor-intensive, which limits its potential for large-scale application. In this paper, a visual-based approach is proposed for the construction of a radio map in anonymous indoor environments. This approach collects multi-sensor data, e.g., Wi-Fi signals, video frames, inertial readings, when people are walking in indoor environments with smartphones in their hands. Then, it spatially recovers the trajectories of people by using both visual and inertial information. Finally, it estimates the location of fingerprints from the trajectories and constructs a Wi-Fi radio map. Experiment results show that the average location error of the fingerprints is about 0.53 m. A weighted k-nearest neighbor method is also used to evaluate the constructed radio map. The average localization error is about 3.2 m, indicating that the quality of the constructed radio map is at the same level as those constructed by site surveying. However, this approach can greatly reduce the human labor cost, which increases the potential for applying it to large indoor environments.<\/jats:p>","DOI":"10.3390\/s17081790","type":"journal-article","created":{"date-parts":[[2017,8,4]],"date-time":"2017-08-04T11:07:08Z","timestamp":1501844828000},"page":"1790","update-policy":"https:\/\/doi.org\/10.3390\/mdpi_crossmark_policy","source":"Crossref","is-referenced-by-count":23,"title":["A Visual-Based Approach for Indoor Radio Map Construction Using Smartphones"],"prefix":"10.3390","volume":"17","author":[{"ORCID":"https:\/\/orcid.org\/0000-0003-2183-8366","authenticated-orcid":false,"given":"Tao","family":"Liu","sequence":"first","affiliation":[{"name":"Shenzhen Key Laboratory of Spatial Smart Sensing and Services, Shenzhen University, Shenzhen 518060, China"},{"name":"Key Laboratory for Geo-Environment Monitoring of Coastal Zone of the National Administration of Surveying, Mapping and Geoinformation, Shenzhen University, Shenzhen 518060, China"}],"role":[{"role":"author","vocabulary":"crossref"}]},{"given":"Xing","family":"Zhang","sequence":"additional","affiliation":[{"name":"Shenzhen Key Laboratory of Spatial Smart Sensing and Services, Shenzhen University, Shenzhen 518060, China"},{"name":"Key Laboratory for Geo-Environment Monitoring of Coastal Zone of the National Administration of Surveying, Mapping and Geoinformation, Shenzhen University, Shenzhen 518060, China"}],"role":[{"role":"author","vocabulary":"crossref"}]},{"given":"Qingquan","family":"Li","sequence":"additional","affiliation":[{"name":"Shenzhen Key Laboratory of Spatial Smart Sensing and Services, Shenzhen University, Shenzhen 518060, China"},{"name":"Key Laboratory for Geo-Environment Monitoring of Coastal Zone of the National Administration of Surveying, Mapping and Geoinformation, Shenzhen University, Shenzhen 518060, China"},{"name":"State Key Laboratory of Information Engineering in Surveying, Mapping and Remote Sensing, Wuhan University, Wuhan 430079, China"}],"role":[{"role":"author","vocabulary":"crossref"}]},{"ORCID":"https:\/\/orcid.org\/0000-0003-1651-878X","authenticated-orcid":false,"given":"Zhixiang","family":"Fang","sequence":"additional","affiliation":[{"name":"State Key Laboratory of Information Engineering in Surveying, Mapping and Remote Sensing, Wuhan University, Wuhan 430079, China"}],"role":[{"role":"author","vocabulary":"crossref"}]}],"member":"1968","published-online":{"date-parts":[[2017,8,4]]},"reference":[{"key":"ref_1","unstructured":"Bahl, P., and Padmanabhan, V.N. (2000, January 26\u201330). RADAR: An in-building RF-based user location and tracking system. Proceedings of the Nineteenth Annual Joint Conference of the IEEE Computer and Communications Societies (INFOCOM), Tel Aviv, Israel."},{"key":"ref_2","doi-asserted-by":"crossref","unstructured":"Bargh, M.S., and Groote, R.D. (2008, January 19). Indoor localization based on response rate of bluetooth inquiries. Proceedings of the ACM International Workshop on Mobile Entity Localization and Tracking in Gps-Less Environments, San Francisco, CA, USA.","DOI":"10.1145\/1410012.1410024"},{"key":"ref_3","doi-asserted-by":"crossref","first-page":"73","DOI":"10.1145\/2508037.2508054","article-title":"LocateMe: Magnetic-fields-based indoor localization using smartphones","volume":"4","author":"Subbu","year":"2013","journal-title":"ACM Trans. Intell. Syst. Technol."},{"key":"ref_4","doi-asserted-by":"crossref","first-page":"536","DOI":"10.1109\/TMC.2006.57","article-title":"Broadband ultrasonic location systems for improved indoor positioning","volume":"5","author":"Hazas","year":"2006","journal-title":"IEEE Trans. Mob. Comput."},{"key":"ref_5","doi-asserted-by":"crossref","first-page":"701","DOI":"10.1023\/B:WINE.0000044029.06344.dd","article-title":"LANDMARC: Indoor location sensing using active RFID","volume":"10","author":"Ni","year":"2004","journal-title":"Wirel. Netw."},{"key":"ref_6","unstructured":"Fontana, R.J., and Gunderson, S.J. (2002, January 21\u201323). Ultra-wideband precision asset location system. Proceedings of the 2002 IEEE Conference on Ultra Wideband Systems and Technologies, Baltimore, MD, USA."},{"key":"ref_7","unstructured":"Zhou, J., Chu, M.K., and Ng, K.Y. (2005, January 25\u201330). Providing location services within a radio cellular network using ellipse propagation model. Proceedings of the International Conference on Advanced Information Networking and Applications, Washington, DC, USA."},{"key":"ref_8","doi-asserted-by":"crossref","unstructured":"Raspopoulos, M., Laoudias, C., Kanaris, L., and Kokkinis, A. (2012, January 27\u201331). Cross device fingerprint-based positioning using 3D Ray Tracing. Proceedings of the 2012 8th International Wireless Communications and Mobile Computing Conference (IWCMC), Limassol, Cyprus.","DOI":"10.1109\/IWCMC.2012.6314193"},{"key":"ref_9","doi-asserted-by":"crossref","first-page":"1031","DOI":"10.1109\/TMC.2014.2343636","article-title":"Joint indoor localization and radio map construction with limited deployment load","volume":"14","author":"Sorour","year":"2013","journal-title":"IEEE Trans. Mob. Comput."},{"key":"ref_10","doi-asserted-by":"crossref","unstructured":"Bolliger, P. (2008, January 19). Redpin\u2014Adaptive, zero-configuration indoor localization through user collaboration. Proceedings of the ACM International Workshop on Mobile Entity Localization and Tracking in Gps-Less Environments, San Francisco, CA, USA.","DOI":"10.1145\/1410012.1410025"},{"key":"ref_11","doi-asserted-by":"crossref","unstructured":"Yang, S., Dessai, P., Verma, M., and Gerla, M. (2013, January 14\u201319). FreeLoc: Calibration-free crowdsourced indoor localization. Proceedings of the 2013 Proceedings IEEE INFOCOM, Turin, Italy.","DOI":"10.1109\/INFCOM.2013.6567054"},{"key":"ref_12","doi-asserted-by":"crossref","first-page":"839","DOI":"10.1109\/TPDS.2012.179","article-title":"WILL: Wireless indoor localization without site survey","volume":"24","author":"Wu","year":"2013","journal-title":"IEEE Trans. Parallel Distrib. Syst."},{"key":"ref_13","doi-asserted-by":"crossref","first-page":"444","DOI":"10.1109\/TMC.2014.2320254","article-title":"Smartphones based crowdsourcing for indoor localization","volume":"14","author":"Wu","year":"2014","journal-title":"IEEE Trans. Mob. Comput."},{"key":"ref_14","doi-asserted-by":"crossref","unstructured":"Yu, N., Xiao, C., Wu, Y., and Feng, R. (2016). A radio-map automatic construction algorithm based on crowdsourcing. Sensors, 16.","DOI":"10.3390\/s16040504"},{"key":"ref_15","doi-asserted-by":"crossref","unstructured":"Youssef, M., and Agrawala, A. (2005, January 6\u20138). The Horus WLAN location determination system. Proceedings of the International Conference on Mobile Systems, Applications, and Services, Seattle, WA, USA.","DOI":"10.1145\/1067170.1067193"},{"key":"ref_16","unstructured":"Castro, P., Chiu, P., Kremenek, T., and Muntz, R. (October, January 30). A probabilistic room location service for wireless networked environments. Proceedings of the 3rd International Conference on Ubiquitous Computing, Atlanta, GA, USA."},{"key":"ref_17","doi-asserted-by":"crossref","first-page":"155","DOI":"10.1023\/A:1016003126882","article-title":"A probabilistic approach to WLAN user location estimation","volume":"9","author":"Roos","year":"2002","journal-title":"Int. J. Wirel. Inf. Netw."},{"key":"ref_18","doi-asserted-by":"crossref","unstructured":"Park, J.G., Charrow, B., Curtis, D., Battat, J., Minkov, E., Hicks, J., Teller, S., and Ledlie, J. (2010, January 15\u201318). Growing an organic indoor location system. Proceedings of the International Conference on Mobile Systems, Applications, and Services, San Francisco, CA, USA.","DOI":"10.1145\/1814433.1814461"},{"key":"ref_19","doi-asserted-by":"crossref","first-page":"2050","DOI":"10.1109\/TMC.2012.175","article-title":"Indoor tracking and navigation using received signal strength and compressive sensing on a mobile device","volume":"12","author":"Au","year":"2013","journal-title":"IEEE Trans. Mob. Comput."},{"key":"ref_20","doi-asserted-by":"crossref","unstructured":"Pratama, A.R., and Hidayat, R. (2012, January 11\u201312). Smartphone-based Pedestrian Dead Reckoning as an indoor positioning system. Proceedings of the International Conference on System Engineering and Technology, Bandung, Indonesia.","DOI":"10.1109\/ICSEngT.2012.6339316"},{"key":"ref_21","doi-asserted-by":"crossref","unstructured":"Gusenbauer, D., Isert, C., and Kr\u00f6sche, J. (2010, January 15\u201317). Self-contained indoor positioning on off-the-shelf mobile devices. Proceedings of the International Conference on Indoor Positioning and Indoor Navigation, Zurich, Switzerland.","DOI":"10.1109\/IPIN.2010.5646681"},{"key":"ref_22","doi-asserted-by":"crossref","unstructured":"Link, J.A.B., Smith, P., Viol, N., and Wehrle, K. (2011, January 21\u201323). FootPath: Accurate map-based indoor navigation using smartphones. Proceedings of the International Conference on Indoor Positioning and Indoor Navigation, Guimaraes, Portugal.","DOI":"10.1109\/IPIN.2011.6071934"},{"key":"ref_23","doi-asserted-by":"crossref","unstructured":"Wang, H., Sen, S., Elgohary, A., Farid, M., Youssef, M., and Choudhury, R.R. (2012, January 25\u201329). No need to war-drive: Unsupervised indoor localization. Proceedings of the International Conference on Mobile Systems, Applications, and Services, Cumbria, UK.","DOI":"10.1145\/2307636.2307655"},{"key":"ref_24","doi-asserted-by":"crossref","unstructured":"House, S., Connell, S., Milligan, I., Austin, D., Hayes, T.L., and Chiang, P. (September, January 30). Indoor localization using pedestrian dead reckoning updated with RFID-based fiducials. Proceedings of the 2011 Annual International Conference of the IEEE Engineering in Medicine and Biology Society, Boston, MA, USA.","DOI":"10.1109\/IEMBS.2011.6091873"},{"key":"ref_25","doi-asserted-by":"crossref","first-page":"715","DOI":"10.3390\/s150100715","article-title":"Fusion of WiFi, smartphone sensors and landmarks using the Kalman filter for indoor localization","volume":"15","author":"Chen","year":"2015","journal-title":"Sensors"},{"key":"ref_26","doi-asserted-by":"crossref","first-page":"562","DOI":"10.1109\/THMS.2014.2368092","article-title":"Activity sequence-based indoor pedestrian localization using smartphones","volume":"45","author":"Zhou","year":"2015","journal-title":"IEEE Trans. Hum.-Mach. Syst."},{"key":"ref_27","unstructured":"Gluckman, J., and Nayar, S.K. (1998, January 7). Ego-motion and omnidirectional cameras. Proceedings of the International Conference on Computer Vision, Bombay, India."},{"key":"ref_28","doi-asserted-by":"crossref","unstructured":"Irani, M., Rousso, B., and Peleg, S. (1994, January 21\u201323). Recovery of ego-motion using image stabilization. Proceedings of the 1994 IEEE Conference on Computer Vision and Pattern Recognition, Seattle, WA, USA.","DOI":"10.1109\/CVPR.1994.323866"},{"key":"ref_29","doi-asserted-by":"crossref","first-page":"215","DOI":"10.1016\/S0921-8890(03)00004-6","article-title":"Rover Navigation using Stereo Ego-motion","volume":"43","author":"Olson","year":"2003","journal-title":"Robot. Auton. Syst."},{"key":"ref_30","doi-asserted-by":"crossref","unstructured":"Milella, A., and Siegwart, R. (2006, January 4\u20137). Stereo-based ego-motion estimation using pixel tracking and iterative closest point. Proceedings of the IEEE International Conference on Computer Vision Systems, New York, NY, USA.","DOI":"10.1109\/ICVS.2006.56"},{"key":"ref_31","doi-asserted-by":"crossref","unstructured":"Porzi, L., Ricci, E., Ciarfuglia, T.A., and Zanin, M. (2012, January 28). Visual-inertial tracking on Android for Augmented Reality applications. Proceedings of the IEEE Workshop on Environmental Energy and Structural Monitoring Systems (EESMS), Perugia, Italy.","DOI":"10.1109\/EESMS.2012.6348402"},{"key":"ref_32","doi-asserted-by":"crossref","unstructured":"Klein, G., and Murray, D. (2007, January 13\u201316). Parallel tracking and mapping for small AR workspaces. Proceedings of the IEEE and ACM International Symposium on Mixed and Augmented Reality, Nara, Japan.","DOI":"10.1109\/ISMAR.2007.4538852"},{"key":"ref_33","doi-asserted-by":"crossref","unstructured":"Mohatta, S., Perla, R., Gupta, G., Hassan, E., and Hebbalaguppe, R. (2017, January 24\u201331). Robust hand gestural interaction for smartphone based AR\/VR applications. Proceedings of the IEEE Winter Conference in Applications of Computer Vision, Santa Rosa, CA, USA.","DOI":"10.1109\/WACV.2017.43"},{"key":"ref_34","doi-asserted-by":"crossref","first-page":"1181","DOI":"10.1109\/TASE.2015.2471175","article-title":"Wearable ego-motion tracking for blind navigation in indoor environments","volume":"12","author":"He","year":"2015","journal-title":"IEEE Trans. Autom. Sci. Eng."},{"key":"ref_35","doi-asserted-by":"crossref","unstructured":"Fang, W., Zheng, L., and Deng, H. (2016, January 11\u201313). A motion tracking method by combining the IMU and camera in mobile devices. Proceedings of the International Conference on Sensing Technology, Nanjing, China.","DOI":"10.1109\/ICSensT.2016.7796235"},{"key":"ref_36","first-page":"5369780","article-title":"A novel metric online monocular SLAM approach for indoor applications","volume":"2016","author":"Li","year":"2016","journal-title":"Sci. Progr."},{"key":"ref_37","doi-asserted-by":"crossref","unstructured":"Ruotsalainen, L., Kuusniemi, H., and Chen, R. (2011, January 21\u201323). Heading change detection for indoor navigation with a Smartphone camera. Proceedings of the International Conference on Indoor Positioning and Indoor Navigation, Guimaraes, Portugal.","DOI":"10.1109\/IPIN.2011.6071924"},{"key":"ref_38","doi-asserted-by":"crossref","first-page":"575","DOI":"10.1007\/s10291-012-0302-8","article-title":"A two-dimensional pedestrian navigation solution aided with a visual gyroscope and a visual odometer","volume":"17","author":"Ruotsalainen","year":"2013","journal-title":"GPS Solut."},{"key":"ref_39","first-page":"433","article-title":"Rover self localization in planetary-like environments","volume":"440","author":"Lacroix","year":"1999","journal-title":"Artif. Intell."},{"key":"ref_40","doi-asserted-by":"crossref","unstructured":"Dong, J., Xiao, Y., Noreikis, M., Ou, Z., and Jaaski, A.Y. (2015, January 1\u20134). iMoon: Using smartphones for image-based indoor navigation. Proceedings of the ACM Conference on Embedded Networked Sensor Systems, Seoul, Korea.","DOI":"10.1145\/2809695.2809722"},{"key":"ref_41","doi-asserted-by":"crossref","first-page":"21636","DOI":"10.3390\/s150921636","article-title":"A probabilistic feature map-based localization system using a monocular camera","volume":"15","author":"Kim","year":"2015","journal-title":"Sensors"},{"key":"ref_42","unstructured":"Jung, S.H., and Taylor, C.J. (2001, January 8\u201314). Camera trajectory estimation using inertial sensor measurements and structure from motion results. Proceedings of the 2001 IEEE Computer Society Conference on Computer Vision and Pattern Recognition, Kauai, HI, USA."},{"key":"ref_43","doi-asserted-by":"crossref","unstructured":"Hakeem, A., Vezzani, R., Shah, M., and Cucchiara, R. (2006, January 20\u201324). Estimating geospatial trajectory of a moving camera. Proceedings of the 18th International Conference on Pattern Recognition, Hong Kong, China.","DOI":"10.1109\/ICPR.2006.499"},{"key":"ref_44","doi-asserted-by":"crossref","first-page":"91","DOI":"10.1023\/B:VISI.0000029664.99615.94","article-title":"Distinctive image features from scale-invariant keypoints","volume":"60","author":"Lowe","year":"2004","journal-title":"Int. J. Comput. Vis."},{"key":"ref_45","unstructured":"Ledwich, L., and Williams, S. (2004, January 6\u20138). Reduced SIFT features for image retrieval and indoor localisation. Proceedings of the Australian Conference on Robotics and Automation, Canberra, Australia."},{"key":"ref_46","doi-asserted-by":"crossref","first-page":"381","DOI":"10.1145\/358669.358692","article-title":"Random sample consensus: A paradigm for model fitting with applications to image analysis and automated cartography","volume":"24","author":"Fischler","year":"1981","journal-title":"Commun. ACM"},{"key":"ref_47","unstructured":"Bouguet, J.Y. (2017, June 01). Camera Calibration Toolbox for Matlab. Available online: http:\/\/www.vision.caltech.edu\/bouguetj\/calib_doc\/."},{"key":"ref_48","doi-asserted-by":"crossref","first-page":"43","DOI":"10.1007\/BF00127818","article-title":"The fundamental matrix: Theory, algorithms, and stability analysis","volume":"17","author":"Luong","year":"1996","journal-title":"Int. J. Comput. Vis."},{"key":"ref_49","doi-asserted-by":"crossref","unstructured":"Hartley, R. (2003). Multiple View Geometry in Computer Vision, Cambridge University Press. [2nd ed.].","DOI":"10.1017\/CBO9780511811685"},{"key":"ref_50","doi-asserted-by":"crossref","first-page":"403","DOI":"10.1007\/BF02163027","article-title":"Singular value decomposition and least squares solutions","volume":"14","author":"Golub","year":"1970","journal-title":"Numer. Math."},{"key":"ref_51","doi-asserted-by":"crossref","unstructured":"Chen, W., Chen, R., Chen, Y., Kuusniemi, H., and Wang, J. (2010, January 4\u20136). An effective Pedestrian Dead Reckoning algorithm using a unified heading error model. Proceedings of the IEEE\/ION Position, Location and Navigation Symposium, Indian Wells, CA, USA.","DOI":"10.1109\/PLANS.2010.5507300"},{"key":"ref_52","doi-asserted-by":"crossref","unstructured":"Alzantot, M., and Youssef, M. (2012, January 1\u20134). UPTIME: Ubiquitous pedestrian tracking using mobile phones. Proceedings of the Wireless Communications and Networking Conference, Shanghai, China.","DOI":"10.1109\/WCNC.2012.6214359"},{"key":"ref_53","doi-asserted-by":"crossref","unstructured":"Mladenov, M., and Mock, M. (2009, January 16). A step counter service for Java-enabled devices using a built-in accelerometer. Proceedings of the 1st International Workshop on Context-Aware Middleware and Services: Affiliated with the 4th International Conference on Communication System Software and Middleware, Dublin, Ireland.","DOI":"10.1145\/1554233.1554235"},{"key":"ref_54","unstructured":"Cho, D.K., Min, M., Lee, U., and Kaiser, W.J. (April, January 29). AutoGait: A mobile platform that accurately estimates the distance walked. Proceedings of the Eigth IEEE International Conference on Pervasive Computing and Communications, Mannheim, Germany."},{"key":"ref_55","doi-asserted-by":"crossref","first-page":"27322","DOI":"10.3390\/s151027322","article-title":"RF-Based Location Using Interpolation Functions to Reduce Fingerprint Mapping","volume":"15","author":"Ezpeleta","year":"2015","journal-title":"Sensors"},{"key":"ref_56","unstructured":"Shen, G., Chen, Z., Zhang, P., Moscibroda, T., and Zhang, Y. (2013, January 2\u20135). Walkie-Markie: Indoor pathway mapping made easy. Proceedings of the Usenix Conference on Networked Systems Design and Implementation, Lombard, IL, USA."}],"container-title":["Sensors"],"original-title":[],"language":"en","link":[{"URL":"https:\/\/www.mdpi.com\/1424-8220\/17\/8\/1790\/pdf","content-type":"unspecified","content-version":"vor","intended-application":"similarity-checking"}],"deposited":{"date-parts":[[2025,10,11]],"date-time":"2025-10-11T18:41:24Z","timestamp":1760208084000},"score":1,"resource":{"primary":{"URL":"https:\/\/www.mdpi.com\/1424-8220\/17\/8\/1790"}},"subtitle":[],"short-title":[],"issued":{"date-parts":[[2017,8,4]]},"references-count":56,"journal-issue":{"issue":"8","published-online":{"date-parts":[[2017,8]]}},"alternative-id":["s17081790"],"URL":"https:\/\/doi.org\/10.3390\/s17081790","relation":{},"ISSN":["1424-8220"],"issn-type":[{"type":"electronic","value":"1424-8220"}],"subject":[],"published":{"date-parts":[[2017,8,4]]}}}