{"status":"ok","message-type":"work","message-version":"1.0.0","message":{"indexed":{"date-parts":[[2026,6,29]],"date-time":"2026-06-29T13:17:32Z","timestamp":1782739052193,"version":"3.54.5"},"reference-count":43,"publisher":"MDPI AG","issue":"4","license":[{"start":{"date-parts":[[2024,2,11]],"date-time":"2024-02-11T00:00:00Z","timestamp":1707609600000},"content-version":"vor","delay-in-days":0,"URL":"https:\/\/creativecommons.org\/licenses\/by\/4.0\/"}],"funder":[{"DOI":"10.13039\/501100004739","name":"Youth Innovation Promotion Association CAS","doi-asserted-by":"publisher","award":["2021409"],"award-info":[{"award-number":["2021409"]}],"id":[{"id":"10.13039\/501100004739","id-type":"DOI","asserted-by":"publisher"}]}],"content-domain":{"domain":[],"crossmark-restriction":false},"short-container-title":["Sensors"],"abstract":"<jats:p>Satellite clock error is a key factor affecting the positioning accuracy of a global navigation satellite system (GNSS). In this paper, we use a gated recurrent unit (GRU) neural network to construct a satellite clock bias forecasting model for the BDS-3 navigation system. In order to further improve the prediction accuracy and stability of the GRU, this paper proposes a satellite clock bias forecasting model, termed ITSSA-GRU, which combines the improved sparrow search algorithm (SSA) and the GRU, avoiding the problems of GRU\u2019s sensitivity to hyperparameters and its tendency to fall into local optimal solutions. The model improves the initialization population phase of the SSA by introducing iterative chaotic mapping and adopts an iterative update strategy based on t-step optimization to enhance the optimization ability of the SSA. Five models, namely, ITSSA-GRU, SSA-GRU, GRU, LSTM, and GM(1,1), are used to forecast the satellite clock bias data in three different types of orbits of the BDS-3 system: MEO, IGSO, and GEO. The experimental results show that, as compared with the other four models, the ITSSA-GRU model has a stronger generalization ability and forecasting effect in the clock bias forecasting of all three types of satellites. Therefore, the ITSSA-GRU model can provide a new means of improving the accuracy of navigation satellite clock bias forecasting to meet the needs of high-precision positioning.<\/jats:p>","DOI":"10.3390\/s24041178","type":"journal-article","created":{"date-parts":[[2024,2,12]],"date-time":"2024-02-12T03:50:27Z","timestamp":1707709827000},"page":"1178","update-policy":"https:\/\/doi.org\/10.3390\/mdpi_crossmark_policy","source":"Crossref","is-referenced-by-count":20,"title":["Improved SSA-Based GRU Neural Network for BDS-3 Satellite Clock Bias Forecasting"],"prefix":"10.3390","volume":"24","author":[{"given":"Hongjie","family":"Liu","sequence":"first","affiliation":[{"name":"College of Computer Science, Xi\u2019an Polytechnic University, Xi\u2019an 710600, China"}],"role":[{"vocabulary":"crossref","role":"author"}]},{"ORCID":"https:\/\/orcid.org\/0000-0001-6320-9635","authenticated-orcid":false,"given":"Feng","family":"Liu","sequence":"additional","affiliation":[{"name":"College of Computer Science, Xi\u2019an Polytechnic University, Xi\u2019an 710600, China"}],"role":[{"vocabulary":"crossref","role":"author"}]},{"given":"Yao","family":"Kong","sequence":"additional","affiliation":[{"name":"College of Electronics and Information, Xi\u2019an Polytechnic University, Xi\u2019an 710600, China"}],"role":[{"vocabulary":"crossref","role":"author"}]},{"ORCID":"https:\/\/orcid.org\/0000-0002-7839-1502","authenticated-orcid":false,"given":"Chaozhong","family":"Yang","sequence":"additional","affiliation":[{"name":"National Time Service Center, Chinese Academy of Sciences, Xi\u2019an 710600, China"}],"role":[{"vocabulary":"crossref","role":"author"}]}],"member":"1968","published-online":{"date-parts":[[2024,2,11]]},"reference":[{"key":"ref_1","doi-asserted-by":"crossref","first-page":"937","DOI":"10.1007\/s10291-016-0583-4","article-title":"Maintaining real-time precise point positioning during outages of orbit and clock corrections","volume":"21","author":"Deo","year":"2017","journal-title":"GPS Solut."},{"key":"ref_2","doi-asserted-by":"crossref","first-page":"475","DOI":"10.1007\/s00190-013-0622-7","article-title":"Initial results of precise orbit and clock determination for COMPASS navigation satellite system","volume":"87","author":"Zhao","year":"2013","journal-title":"J. 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