{"status":"ok","message-type":"work","message-version":"1.0.0","message":{"indexed":{"date-parts":[[2026,4,29]],"date-time":"2026-04-29T22:36:33Z","timestamp":1777502193432,"version":"3.51.4"},"reference-count":32,"publisher":"MDPI AG","issue":"1","license":[{"start":{"date-parts":[[2023,1,2]],"date-time":"2023-01-02T00:00:00Z","timestamp":1672617600000},"content-version":"vor","delay-in-days":0,"URL":"https:\/\/creativecommons.org\/licenses\/by\/4.0\/"}],"funder":[{"name":"Special Fund of Hubei Luojia Laboratory","award":["No. 220100013"],"award-info":[{"award-number":["No. 220100013"]}]}],"content-domain":{"domain":[],"crossmark-restriction":false},"short-container-title":["Sensors"],"abstract":"<jats:p>The real-time information of the unknown ionospheric environments is difficult to obtain, plaguing the timely and accurate geolocation of high frequency (HF) sources. In this paper, we propose an improved HF skywave source geolocation method based on the time-difference-of-arrival (TDOA) with the semidefinite programming (SDP), and model HF signal propagation paths as paths with significant non-line-of-sight (NLOS) biases. With this method, no priori information about the ionosphere, especially the priori ionospheric virtual heights of reflection, is necessary while timely and accurately geolocating the HF sources. Furthermore, we use the ray tracing technique and build a 3D ionospheric electron density gridded matrix model to simulate realistic HF signal propagation paths. In the simulations, the proposed method is compared with existing methods, and detailed geolocation error distribution maps are given. In the experiments, HF I\/Q data captured from different types of HF transmitters are located by six receivers with time synchronization. Simulated and experimental results show that the proposed method improves the positioning accuracy by about 50% compared with existing methods under the same conditions, and the average relative positioning error is less than 2.7%.<\/jats:p>","DOI":"10.3390\/s23010507","type":"journal-article","created":{"date-parts":[[2023,1,3]],"date-time":"2023-01-03T02:33:21Z","timestamp":1672713201000},"page":"507","update-policy":"https:\/\/doi.org\/10.3390\/mdpi_crossmark_policy","source":"Crossref","is-referenced-by-count":4,"title":["An Improved TDOA Method for Land-Based Long-Range HF Skywave Source Geolocation and Experimental Results"],"prefix":"10.3390","volume":"23","author":[{"given":"Chen","family":"Xu","sequence":"first","affiliation":[{"name":"School of Electronics and Information, Wuhan University, Wuhan 430072, China"},{"name":"Hubei Luojia Laboratory, Wuhan 430072, China"}],"role":[{"role":"author","vocabulary":"crossref"}]},{"given":"Hongtao","family":"Cai","sequence":"additional","affiliation":[{"name":"School of Electronics and Information, Wuhan University, Wuhan 430072, China"},{"name":"Hubei Luojia Laboratory, Wuhan 430072, China"}],"role":[{"role":"author","vocabulary":"crossref"}]},{"given":"Shunzu","family":"Gao","sequence":"additional","affiliation":[{"name":"School of Electronics and Information, Wuhan University, Wuhan 430072, China"},{"name":"Hubei Luojia Laboratory, Wuhan 430072, China"}],"role":[{"role":"author","vocabulary":"crossref"}]},{"given":"Qingwei","family":"Zhai","sequence":"additional","affiliation":[{"name":"The 54th Research Institute of China Electronics Technology Group Corporation (CETC 54), Shijiazhuang 050000, China"}],"role":[{"role":"author","vocabulary":"crossref"}]}],"member":"1968","published-online":{"date-parts":[[2023,1,2]]},"reference":[{"key":"ref_1","unstructured":"McNamara, L.F. 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