{"status":"ok","message-type":"work","message-version":"1.0.0","message":{"indexed":{"date-parts":[[2026,2,26]],"date-time":"2026-02-26T05:03:56Z","timestamp":1772082236132,"version":"3.50.1"},"reference-count":29,"publisher":"MDPI AG","issue":"4","license":[{"start":{"date-parts":[[2023,2,16]],"date-time":"2023-02-16T00:00:00Z","timestamp":1676505600000},"content-version":"vor","delay-in-days":0,"URL":"https:\/\/creativecommons.org\/licenses\/by\/4.0\/"}],"funder":[{"name":"Spanish Ministry of Economy, Industry and Competitiveness, FEDER","award":["PID2019-103871GB-I00"],"award-info":[{"award-number":["PID2019-103871GB-I00"]}]},{"name":"Spanish Ministry of Economy, Industry and Competitiveness, FEDER","award":["1380047-F UCOFEDER-2021"],"award-info":[{"award-number":["1380047-F UCOFEDER-2021"]}]},{"DOI":"10.13039\/501100002924","name":"European Union","doi-asserted-by":"publisher","award":["PID2019-103871GB-I00"],"award-info":[{"award-number":["PID2019-103871GB-I00"]}],"id":[{"id":"10.13039\/501100002924","id-type":"DOI","asserted-by":"publisher"}]},{"DOI":"10.13039\/501100002924","name":"European Union","doi-asserted-by":"publisher","award":["1380047-F UCOFEDER-2021"],"award-info":[{"award-number":["1380047-F UCOFEDER-2021"]}],"id":[{"id":"10.13039\/501100002924","id-type":"DOI","asserted-by":"publisher"}]}],"content-domain":{"domain":[],"crossmark-restriction":false},"short-container-title":["Sensors"],"abstract":"<jats:p>Environment landmarks are generally employed by visual SLAM (vSLAM) methods in the form of keypoints. However, these landmarks are unstable over time because they belong to areas that tend to change, e.g., shadows or moving objects. To solve this, some other authors have proposed the combination of keypoints and artificial markers distributed in the environment so as to facilitate the tracking process in the long run. Artificial markers are special elements (similar to beacons) that can be permanently placed in the environment to facilitate tracking. In any case, these systems keep a set of keypoints that is not likely to be reused, thus unnecessarily increasing the computing time required for tracking. This paper proposes a novel visual SLAM approach that efficiently combines keypoints and artificial markers, allowing for a substantial reduction in the computing time and memory required without noticeably degrading the tracking accuracy. In the first stage, our system creates a map of the environment using both keypoints and artificial markers, but once the map is created, the keypoints are removed and only the markers are kept. Thus, our map stores only long-lasting features of the environment (i.e., the markers). Then, for localization purposes, our algorithm uses the marker information along with temporary keypoints created just in the time of tracking, which are removed after a while. Since our algorithm keeps only a small subset of recent keypoints, it is faster than the state-of-the-art vSLAM approaches. The experimental results show that our proposed sSLAM compares favorably with ORB-SLAM2, ORB-SLAM3, OpenVSLAM and UcoSLAM in terms of speed, without statistically significant differences in accuracy.<\/jats:p>","DOI":"10.3390\/s23042210","type":"journal-article","created":{"date-parts":[[2023,2,16]],"date-time":"2023-02-16T01:36:52Z","timestamp":1676511412000},"page":"2210","update-policy":"https:\/\/doi.org\/10.3390\/mdpi_crossmark_policy","source":"Crossref","is-referenced-by-count":10,"title":["sSLAM: Speeded-Up Visual SLAM Mixing Artificial Markers and Temporary Keypoints"],"prefix":"10.3390","volume":"23","author":[{"ORCID":"https:\/\/orcid.org\/0000-0002-9572-0128","authenticated-orcid":false,"given":"Francisco J.","family":"Romero-Ramirez","sequence":"first","affiliation":[{"name":"Departamento de Inform\u00e1tica y An\u00e1lisis Num\u00e9rico, Edificio Einstein, Campus de Rabanales, Universidad de Co\u0155doba, 14071 C\u00f3rdoba, Spain"},{"name":"Departamento de Ciencia de la Computaci\u00f3n e Inteligencia Artificial, Universidad de Alicante, Carretera San Vicente del Raspeig s\/n, 03690 San Vicente del Raspeig, Spain"}],"role":[{"role":"author","vocabulary":"crossref"}]},{"ORCID":"https:\/\/orcid.org\/0000-0002-8773-8571","authenticated-orcid":false,"given":"Rafael","family":"Mu\u00f1oz-Salinas","sequence":"additional","affiliation":[{"name":"Departamento de Inform\u00e1tica y An\u00e1lisis Num\u00e9rico, Edificio Einstein, Campus de Rabanales, Universidad de Co\u0155doba, 14071 C\u00f3rdoba, Spain"},{"name":"Instituto Maim\u00f3nides de Investigaci\u00f3n en Biomedicina (IMIBIC), Avenida Men\u00e9ndez Pidal s\/n, 14004 C\u00f3rdoba, Spain"}],"role":[{"role":"author","vocabulary":"crossref"}]},{"ORCID":"https:\/\/orcid.org\/0000-0001-9294-6714","authenticated-orcid":false,"given":"Manuel J.","family":"Mar\u00edn-Jim\u00e9nez","sequence":"additional","affiliation":[{"name":"Departamento de Inform\u00e1tica y An\u00e1lisis Num\u00e9rico, Edificio Einstein, Campus de Rabanales, Universidad de Co\u0155doba, 14071 C\u00f3rdoba, Spain"},{"name":"Instituto Maim\u00f3nides de Investigaci\u00f3n en Biomedicina (IMIBIC), Avenida Men\u00e9ndez Pidal s\/n, 14004 C\u00f3rdoba, Spain"}],"role":[{"role":"author","vocabulary":"crossref"}]},{"ORCID":"https:\/\/orcid.org\/0000-0001-6805-3633","authenticated-orcid":false,"given":"Miguel","family":"Cazorla","sequence":"additional","affiliation":[{"name":"Departamento de Ciencia de la Computaci\u00f3n e Inteligencia Artificial, Universidad de Alicante, Carretera San Vicente del Raspeig s\/n, 03690 San Vicente del Raspeig, Spain"}],"role":[{"role":"author","vocabulary":"crossref"}]},{"ORCID":"https:\/\/orcid.org\/0000-0003-4481-0614","authenticated-orcid":false,"given":"Rafael","family":"Medina-Carnicer","sequence":"additional","affiliation":[{"name":"Departamento de Inform\u00e1tica y An\u00e1lisis Num\u00e9rico, Edificio Einstein, Campus de Rabanales, Universidad de Co\u0155doba, 14071 C\u00f3rdoba, Spain"},{"name":"Instituto Maim\u00f3nides de Investigaci\u00f3n en Biomedicina (IMIBIC), Avenida Men\u00e9ndez Pidal s\/n, 14004 C\u00f3rdoba, Spain"}],"role":[{"role":"author","vocabulary":"crossref"}]}],"member":"1968","published-online":{"date-parts":[[2023,2,16]]},"reference":[{"key":"ref_1","doi-asserted-by":"crossref","first-page":"16","DOI":"10.1186\/s41074-017-0027-2","article-title":"Visual SLAM algorithms: A survey from 2010 to 2016","volume":"9","author":"Taketomi","year":"2017","journal-title":"IPSJ Trans. 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