# An Interactive Transient Model Correction Active Sonar Target Tracking Method
## 4 Conclusions  
In order to solve problems such as state model mismatch and tracking accuracy decline caused by changes underwater target motion states, this study investigated and proposed the TMC tracking method, which innovatively adopts the idea of real-time model correction. Firstly, a KF filter is applied to track the target detected by sonar. The proportion of newly entered measurement information in the forecast output will be smaller and smaller, so that the KF filter cannot keep up with the change in the target state in time. At this time, by comparing the residual covariance of the KF filter with the threshold generated by sonar measurement error, the change in the target motion state can be judged in real time. Then, a constant gain filter is used to modify the target motion model so that it is closer to the real motion state of the target so as to achieve the purpose of transient correction of the KF filter and to improve the precision of the target tracking output. Simulation verification and offshore testing showed that the TMC tracking method could improve the tracking accuracy of active sonar on underwater targets compared with the conventional KF method.  
Figure 9: RMSE of distances and azimuths. (**a**) RMSE of position distances, (**b**) RMSE of azimuths.  
In this research, it was found that variation in the position measurement error of an active sonar on an underwater target will affect the performance of the TMC tracking method. In addition, based on the fact that active sonar can only measure the radial distance and azimuth of a target in real time, this study only established a two-dimensional motion model of a target. If active sonar can measure the target information of more dimensions in real time, such as velocity information, then the algorithm model can be extended to a higher dimension, the corresponding constant gain filter used for transient model correction will also adopt a higher dimension filter (such as \(\alpha\)-\(\beta\)-\(\gamma\) filter, etc.), and the algorithm processing effect will be better. Both are worth continuing.  
Conceptualization, C.L. and S.F.; methodology, S.F. and C.L.; software, C.L.; validation, C.L. and S.F.; formal analysis, C.L.; investigation, C.L. and S.F.; resources, S.F.; data curation, C.L. and S.F.; writing--original draft preparation, C.L; writing--review and editing, C.L. and S.F.; visualization, C.L.; supervision, S.F.; project administration, S.F.; funding acquisition, S.F. All authors have read and agreed to the published version of the manuscript.  
This research received no external funding.  
Not applicable.  
The data that support the findings of this study are available from the corresponding author upon reasonable request.  
[PERSON] has conducted a lot of work in the collection, analysis and processing of offshore testing data, and put forward useful suggestions for the experimental verification of the TMC method. [PERSON] and [PERSON] provided specific assistance in the language, text and structure of the article. I would like to express my sincere thanks to them for their hard work and helpful help.  
The authors declare no conflict of interest.