{"status":"ok","message-type":"work","message-version":"1.0.0","message":{"indexed":{"date-parts":[[2025,10,11]],"date-time":"2025-10-11T19:11:29Z","timestamp":1760209889462,"version":"build-2065373602"},"reference-count":34,"publisher":"MDPI AG","issue":"8","license":[{"start":{"date-parts":[[2017,8,10]],"date-time":"2017-08-10T00:00:00Z","timestamp":1502323200000},"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>In this paper, we address the generation of semantic labels describing the headgear accessories carried out by people in a scene under surveillance, only using depth information obtained from a Time-of-Flight (ToF) camera placed in an overhead position. We propose a new method for headgear accessories classification based on the design of a robust processing strategy that includes the estimation of a meaningful feature vector that provides the relevant information about the people\u2019s head and shoulder areas. This paper includes a detailed description of the proposed algorithmic approach, and the results obtained in tests with persons with and without headgear accessories, and with different types of hats and caps. In order to evaluate the proposal, a wide experimental validation has been carried out on a fully labeled database (that has been made available to the scientific community), including a broad variety of people and headgear accessories. For the validation, three different levels of detail have been defined, considering a different number of classes: the first level only includes two classes (hat\/cap, and no hat\/cap), the second one considers three classes (hat, cap and no hat\/cap), and the last one includes the full class set with the five classes (no hat\/cap, cap, small size hat, medium size hat, and large size hat). The achieved performance is satisfactory in every case: the average classification rates for the first level reaches 95.25%, for the second one is 92.34%, and for the full class set equals 84.60%. In addition, the online stage processing time is 5.75 ms per frame in a standard PC, thus allowing for real-time operation.<\/jats:p>","DOI":"10.3390\/s17081845","type":"journal-article","created":{"date-parts":[[2017,8,10]],"date-time":"2017-08-10T10:34:35Z","timestamp":1502361275000},"page":"1845","update-policy":"https:\/\/doi.org\/10.3390\/mdpi_crossmark_policy","source":"Crossref","is-referenced-by-count":1,"title":["Headgear Accessories Classification Using an Overhead Depth Sensor"],"prefix":"10.3390","volume":"17","author":[{"given":"Carlos","family":"Luna","sequence":"first","affiliation":[{"name":"Department of Electronics, University of Alcala, Ctra. Madrid-Barcelona, km.33,600, 28805 Alcal\u00e1 de Henares, Spain"}],"role":[{"role":"author","vocabulary":"crossref"}]},{"ORCID":"https:\/\/orcid.org\/0000-0002-3303-3963","authenticated-orcid":false,"given":"Javier","family":"Macias-Guarasa","sequence":"additional","affiliation":[{"name":"Department of Electronics, University of Alcala, Ctra. Madrid-Barcelona, km.33,600, 28805 Alcal\u00e1 de Henares, Spain"}],"role":[{"role":"author","vocabulary":"crossref"}]},{"ORCID":"https:\/\/orcid.org\/0000-0001-9545-327X","authenticated-orcid":false,"given":"Cristina","family":"Losada-Gutierrez","sequence":"additional","affiliation":[{"name":"Department of Electronics, University of Alcala, Ctra. Madrid-Barcelona, km.33,600, 28805 Alcal\u00e1 de Henares, Spain"}],"role":[{"role":"author","vocabulary":"crossref"}]},{"ORCID":"https:\/\/orcid.org\/0000-0001-7723-2262","authenticated-orcid":false,"given":"Marta","family":"Marron-Romera","sequence":"additional","affiliation":[{"name":"Department of Electronics, University of Alcala, Ctra. Madrid-Barcelona, km.33,600, 28805 Alcal\u00e1 de Henares, Spain"}],"role":[{"role":"author","vocabulary":"crossref"}]},{"given":"Manuel","family":"Mazo","sequence":"additional","affiliation":[{"name":"Department of Electronics, University of Alcala, Ctra. Madrid-Barcelona, km.33,600, 28805 Alcal\u00e1 de Henares, Spain"}],"role":[{"role":"author","vocabulary":"crossref"}]},{"given":"Sara","family":"Luengo-Sanchez","sequence":"additional","affiliation":[{"name":"Department of Electronics, University of Alcala, Ctra. Madrid-Barcelona, km.33,600, 28805 Alcal\u00e1 de Henares, Spain"}],"role":[{"role":"author","vocabulary":"crossref"}]},{"given":"Roberto","family":"Macho-Pedroso","sequence":"additional","affiliation":[{"name":"Department of Electronics, University of Alcala, Ctra. Madrid-Barcelona, km.33,600, 28805 Alcal\u00e1 de Henares, Spain"}],"role":[{"role":"author","vocabulary":"crossref"}]}],"member":"1968","published-online":{"date-parts":[[2017,8,10]]},"reference":[{"key":"ref_1","doi-asserted-by":"crossref","first-page":"390","DOI":"10.1109\/3.910448","article-title":"Solid-state Time-of-Flight range camera","volume":"37","author":"Lange","year":"2001","journal-title":"IEEE J. Quantum Electron."},{"key":"ref_2","doi-asserted-by":"crossref","first-page":"44","DOI":"10.1109\/MM.2014.9","article-title":"The Xbox one system on a chip and kinect sensor","volume":"34","author":"Sell","year":"2014","journal-title":"IEEE Micro"},{"key":"ref_3","doi-asserted-by":"crossref","unstructured":"Kerker, D., Jenkins, M.P., Gross, G.A., Bisantz, A.M., and Nagi, R. (2014, January 3\u20136). Visual estimation of human attributes: An empirical study of context-dependent human observation capabilities. Proceedings of the 2014 IEEE International Inter-Disciplinary Conference on Cognitive Methods in Situation Awareness and Decision Support (CogSIMA), San Antonio, TX, USA.","DOI":"10.1109\/CogSIMA.2014.6816538"},{"key":"ref_4","doi-asserted-by":"crossref","unstructured":"Saranya, M., Cyril, G.L.I., and Santhosh, R.R. (2016, January 3\u20135). An approach towards ear feature extraction for human identification. Proceedings of the 2016 International Conference on Electrical, Electronics, and Optimization Techniques (ICEEOT), Chennai, India.","DOI":"10.1109\/ICEEOT.2016.7755636"},{"key":"ref_5","doi-asserted-by":"crossref","unstructured":"Kim, S.T., Kim, D.H., and Ro, Y.M. (2016, January 25\u201328). Spatio-temporal representation for face authentication by using multi-task learning with human attributes. Proceedings of the 2016 IEEE International Conference on Image Processing (ICIP), Phoenix, AZ, USA.","DOI":"10.1109\/ICIP.2016.7532909"},{"key":"ref_6","doi-asserted-by":"crossref","unstructured":"Wang, H.-J., Lin, Y.-L., Huang, C.-Y., Hou, Y.-L., and Hsu, W. (2013, January 27\u201330). Full body human attribute detection in indoor surveillance environment using color-depth information. Proceedings of the 2013 10th IEEE International Conference on Advanced Video and Signal Based Surveillance, Krakow, Poland.","DOI":"10.1109\/AVSS.2013.6636670"},{"key":"ref_7","doi-asserted-by":"crossref","unstructured":"Linder, T., and Arras, K.O. (October, January 28). Real-time full-body human attribute classification in RGB-D using a tessellation boosting approach. Proceedings of the 2015 IEEE\/RSJ International Conference on Intelligent Robots and Systems (IROS), Hamburg, Germany.","DOI":"10.1109\/IROS.2015.7353541"},{"key":"ref_8","doi-asserted-by":"crossref","unstructured":"Chen, H., Gallagher, A., and Girod, B. (2012, January 7\u201313). Describing clothing by semantic attributes. Proceedings of the European Conference on Computer Vision, Florence, Italy.","DOI":"10.1007\/978-3-642-33712-3_44"},{"key":"ref_9","doi-asserted-by":"crossref","unstructured":"Bourdev, L., Maji, S., and Malik, J. (2011, January 6\u201313). Describing people: A poselet-based approach to attribute classification. Proceedings of the 2011 International Conference on Computer Vision, Barcelona, Spain.","DOI":"10.1109\/ICCV.2011.6126413"},{"key":"ref_10","doi-asserted-by":"crossref","unstructured":"Wang, N., and Ai, H. (2011, January 28). Hair style retrieval by semantic mapping on informative patches. Proceedings of the First Asian Conference on Pattern Recognition, Beijing, China.","DOI":"10.1109\/ACPR.2011.6166682"},{"key":"ref_11","doi-asserted-by":"crossref","unstructured":"Linder, T., Wehner, S., and Arras, K.O. (2015, January 26\u201330). Real-time full-body human gender recognition in (RGB)-D data. Proceedings of the 2015 IEEE International Conference on Robotics and Automation (ICRA), Seattle, WA, USA.","DOI":"10.1109\/ICRA.2015.7139616"},{"key":"ref_12","doi-asserted-by":"crossref","first-page":"993","DOI":"10.1587\/transinf.E96.D.993","article-title":"Human attribute analysis using a top-view camera based on two-stage classification","volume":"E96-D","author":"Yamasaki","year":"2013","journal-title":"IEICE Trans. Inf. Syst."},{"key":"ref_13","doi-asserted-by":"crossref","unstructured":"Bevilacqua, A., Di Stefano, L., and Azzari, P. (2006, January 22\u201324). People tracking using a time-of-flight depth sensor. Proceedings of the 2006 IEEE International Conference on Video and Signal Based Surveillance, Sydney, Australia.","DOI":"10.1109\/AVSS.2006.92"},{"key":"ref_14","first-page":"213","article-title":"People detection and tracking from a top-view position using a Time-of-Flight camera","volume":"Volume 368","author":"Dziech","year":"2013","journal-title":"Communications in Computer and Information Science, Proceedings of the International Conference on Multimedia Communications, Services and Security, Krak\u00f3w, Poland, 6\u20137 June 2013"},{"key":"ref_15","doi-asserted-by":"crossref","first-page":"689","DOI":"10.1109\/TII.2013.2251892","article-title":"Using Time-of-Flight measurements for privacy-preserving tracking in a smart room","volume":"10","author":"Jia","year":"2014","journal-title":"IEEE Trans. Ind. Inform."},{"key":"ref_16","doi-asserted-by":"crossref","unstructured":"Cai, Z., Yu, Z.L., Liu, H., and Zhang, K. (2014, January 9\u201311). Counting people in crowded scenes by video analyzing. Proceedings of the 2014 9th IEEE Conference on Industrial Electronics and Applications, Hangzhou, China.","DOI":"10.1109\/ICIEA.2014.6931467"},{"key":"ref_17","doi-asserted-by":"crossref","unstructured":"Gal\u010d\u00edk, F., and Gargal\u00edk, R. (2013, January 28\u201331). Real-time depth map based people counting. Proceedings of the International Conference on Advanced Concepts for Intelligent Vision Systems, Pozna\u0144, Poland.","DOI":"10.1007\/978-3-319-02895-8_30"},{"key":"ref_18","doi-asserted-by":"crossref","unstructured":"Rauter, M. (2013, January 23\u201328). Reliable human detection and tracking in top-view depth images. Proceedings of the 2013 IEEE Conference on Computer Vision and Pattern Recognition Workshops, Portland, OR, USA.","DOI":"10.1109\/CVPRW.2013.84"},{"key":"ref_19","doi-asserted-by":"crossref","first-page":"41","DOI":"10.1016\/j.patrec.2016.05.033","article-title":"Counting people by RGB or depth overhead cameras","volume":"81","author":"Foggia","year":"2016","journal-title":"Pattern Recognit. Lett."},{"key":"ref_20","doi-asserted-by":"crossref","first-page":"303","DOI":"10.1007\/s00138-015-0739-1","article-title":"Counting pedestrians with a zenithal arrangement of depth cameras","volume":"27","author":"Vera","year":"2016","journal-title":"Mach. Vis. Appl."},{"key":"ref_21","doi-asserted-by":"crossref","first-page":"240","DOI":"10.1016\/j.eswa.2016.11.019","article-title":"Robust people detection using depth information from an overhead Time-of-Flight camera","volume":"71","author":"Luna","year":"2016","journal-title":"Expert Syst. Appl."},{"key":"ref_22","doi-asserted-by":"crossref","unstructured":"Jimenez, D., Pizarro, D., Mazo, M., and Palazuelos, S. (2012, January 16\u201321). Modelling and correction of multipath interference in Time of Flight cameras. Proceedings of the 2012 IEEE Conference on Computer Vision and Pattern Recognition, Providence, RI, USA.","DOI":"10.1109\/CVPR.2012.6247763"},{"key":"ref_23","doi-asserted-by":"crossref","first-page":"1127","DOI":"10.1016\/j.imavis.2014.08.014","article-title":"Single frame correction of motion artifacts in PMD-based Time of Flight cameras","volume":"32","author":"Jimenez","year":"2014","journal-title":"Image Vis. Comput."},{"key":"ref_24","doi-asserted-by":"crossref","unstructured":"He, Y., Liang, B., Zou, Y., He, J., and Yang, J. (2017). Depth errors analysis and correction for Time-of-Flight (ToF) cameras. Sensors, 17.","DOI":"10.3390\/s17010092"},{"key":"ref_25","doi-asserted-by":"crossref","unstructured":"Zhu, L., and Wong, K.-H. (2013, January 29\u201331). Human tracking and counting using the kinect range sensor based on adaboost and kalman filter. Proceedings of the International Symposium on Visual Computing, Rethymnon, Greece.","DOI":"10.1007\/978-3-642-41939-3_57"},{"key":"ref_26","doi-asserted-by":"crossref","unstructured":"Matzner, S., Heredia-Langner, A., Amidan, B., Boettcher, E.J., Lochtefeld, D., and Webb, T. (2015, January 14\u201316). Standoff human identification using body shape. Proceedings of the 2015 IEEE International Symposium on Technologies for Homeland Security (HST), Waltham, MA, USA.","DOI":"10.1109\/THS.2015.7225300"},{"key":"ref_27","doi-asserted-by":"crossref","first-page":"1286","DOI":"10.1136\/adc.67.10.1286","article-title":"Centiles for adult head circumference","volume":"67","author":"Bushby","year":"1992","journal-title":"Arch. Dis. Child."},{"key":"ref_28","doi-asserted-by":"crossref","unstructured":"Seidenari, L., Varano, V., Berretti, S., Del Bimbo, A., and Pala, P. (2013, January 23\u201328). Recognizing actions from depth cameras as weakly aligned multi-part bag-of-poses. Proceedings of the 2013 IEEE Conference on Computer Vision and Pattern Recognition Workshops, Portland, OR, USA.","DOI":"10.1109\/CVPRW.2013.77"},{"key":"ref_29","doi-asserted-by":"crossref","first-page":"1505","DOI":"10.1109\/TPAMI.2003.1251144","article-title":"Silhouette analysis-based gait recognition for human identification","volume":"25","author":"Wang","year":"2003","journal-title":"Pattern Anal. Mach. Intell."},{"key":"ref_30","doi-asserted-by":"crossref","first-page":"4825","DOI":"10.3390\/s100504825","article-title":"GPCA vs. PCA in recognition and 3-D localization of ultrasound reflectors","volume":"10","author":"Luna","year":"2010","journal-title":"Sensors"},{"key":"ref_31","unstructured":"Fernandez-Rincon, A., Fuentes-Jimenez, D., Losada-Gutierrez, C., Marron-Romera, M., Luna, C.A., Macias-Guarasa, J., and Mazo, M. (March, January 27). Robust people detection and tracking from an overhead Time-of-Flight camera. Proceedings of the 12th International Joint Conference on Computer Vision, Imaging and Computer Graphics Theory and Applications, Porto, Portugal."},{"key":"ref_32","unstructured":"Macias-Guarasa, J., Losada-Gutierrez, C., Fuentes-Jimenez, D., Garcia-Jimenez, R., Luna, C.A., Fernandez-Rincon, A., and Mazo, M. (2017, July 31). GEINTRA Overhead ToF People Detection (GOTPD1) Database. Available online: http:\/\/www.geintra-uah.org\/datasets\/gotpd1."},{"key":"ref_33","doi-asserted-by":"crossref","first-page":"1437","DOI":"10.3390\/s120201437","article-title":"Accuracy and resolution of kinect depth data for indoor mapping applications","volume":"12","author":"Khoshelham","year":"2012","journal-title":"Sensors"},{"key":"ref_34","doi-asserted-by":"crossref","unstructured":"Sahani, M., Nanda, C., Sahu, A.K., and Pattnaik, B. (2015, January 19\u201320). Web-based online embedded door access control and home security system based on face recognition. Proceedings of the 2015 International Conference on Circuits, Power and Computing Technologies [ICCPCT], Nagercoil, India.","DOI":"10.1109\/ICCPCT.2015.7159473"}],"container-title":["Sensors"],"original-title":[],"language":"en","link":[{"URL":"https:\/\/www.mdpi.com\/1424-8220\/17\/8\/1845\/pdf","content-type":"unspecified","content-version":"vor","intended-application":"similarity-checking"}],"deposited":{"date-parts":[[2025,10,11]],"date-time":"2025-10-11T18:42:01Z","timestamp":1760208121000},"score":1,"resource":{"primary":{"URL":"https:\/\/www.mdpi.com\/1424-8220\/17\/8\/1845"}},"subtitle":[],"short-title":[],"issued":{"date-parts":[[2017,8,10]]},"references-count":34,"journal-issue":{"issue":"8","published-online":{"date-parts":[[2017,8]]}},"alternative-id":["s17081845"],"URL":"https:\/\/doi.org\/10.3390\/s17081845","relation":{},"ISSN":["1424-8220"],"issn-type":[{"type":"electronic","value":"1424-8220"}],"subject":[],"published":{"date-parts":[[2017,8,10]]}}}