*Article* **Analysis of Regional Satellite Clock Bias Characteristics Based on BeiDou System**

**Wenxuan Liu 1, Hu Wang 1,\*, Hongyang Ma 2, Yingyan Cheng 1, Pengyuan Li 3, Bo Li <sup>4</sup> and Yingying Ren <sup>3</sup>**

<sup>1</sup> Chinese Academy of Surveying & Mapping, Beijing 100036, China

	- <sup>4</sup> School of Geomatics, Liaoning Technical University, Fuxin 123000, China
	- **\*** Correspondence: wanghu@casm.ac.cn; Tel.: +86-15652077998

**Abstract:** With the continuous development of the Global Navigation Satellite System (GNSS), the calculation theory and strategy of the global Satellite Clock Bias (SCB) tends to be mature. However, in some eventualities with restricted conditions, the calculation and application of the global SCB are limited; hence, the application of regional SCB is derived. This paper focuses on the quality of regional SCB products in different regions, calculates three groups of regional SCB products, and analyzes their properties and application effects. We expand the double-differenced assessment method for SCB and extend satellite clock accuracy assessment to regional satellite clock products. Additionally, the Regional Effect Bias (REB) is introduced to analyze the influence of the relative position of satellite geometry on the SCB products due to the regional effects. The conclusions are as follows: (1) In low-latitude regions, SCB products have a high degree of completeness and a large number of satellite observations, which is conducive to expanding the positioning application range of regional SCB; (2) the low-latitude regions SCB will be affected by ionospheric activity, and the accuracy will be slightly lower than that of satellite clocks deviation in mid-latitudes; (3) in this paper, the REB in this area is in the level of 10<sup>−</sup>7. The experiment displays the result that the values of REB in low-latitude areas are larger, leading to fluctuated Precise Point Position (PPP) results. However, there are fewer stations in the mid-latitude regions, which will also affect the accuracy of PPP; (4) the accuracy of the positioning results of the regional satellite clock deviation in the Chinese region is higher than that of the global clock.

**Keywords:** precise point positioning; clock estimation; station network
