# Analysis of the Development Status of eLoran Time Service System in China
## 4 Current Situation of the Construction of eLoran Time Service in China  
In order to meet the needs of eLoran signal blind spot users in the western, northwestern, and southwestern regions of China and to consider the overall layout of the eLoran  
Figure 2: Coverage of time service signals at existing eLoran stations in China.  
system in China, the high-precision ground-based time service system was approved in 2016. This specifies the construction of a high-precision ground-based time service system, which mainly utilizes the high reliability and high-precision technical features of the eLoran time service and fiber optic time service technologies to build a highly reliable and high-precision ground-based time service system that is relatively independent, integrated, shared, backup, complementary, and mutually reinforces satellite navigation.. Combined with the existing eLoran system, it basically achieves the national coverage of eLoran time service signals.  
The project conducted theoretical calculations and actual measurements of the coverage range of the existing loran ground wave timing signals. The results showed that due to system layout reasons, there is a large coverage blind spot for the existing eLoran signal in the west, with a blind spot length of about 2100 km from east to west and a width of about 2300 km from north to south. At the same time, the western region is important, with high requirements for the safety and reliability of the time service. It is necessary to have an eLoran time service system that complements the satellite navigation system time service to provide a time service. It is necessary to add and build time service broadcasting stations to meet the coverage needs. Therefore, taking into account some factors, such as the current signal coverage status and construction costs in China, combined with the future navigation expansion needs, three eLoran time service broadcasting stations will be added and constructed in Dunhuang, Korla, and Naqu in the western region. The layout of eLoran system in China is shown in Figure 3.  
Figure 3: Layout of eLoran system in China.  
At the same time, in order to improve the application accuracy of the existing and new eLoran systems, the high-precision ground-based time service system plans are to build multiple eLoran differential enhancement stations nationwide. However, due to the vastness of our country, there is a huge demand for differential station construction. At the same time, considering the economic cost of construction and the urgency of the demand, the layout of differential enhancement stations should first meet the high-precision time service needs of the key and critical areas in China. By using eLoran differential enhancement technology, a time service accuracy better than 100 ns can be achieved. The high-precision ground-based time service system is currently the most accurate large-scale land-based radio time service system. After the system has been built, it can improve the accuracy of the eLoran time service to a level equivalent to that of the satellite navigation system, and thus achieve a combined and enhanced space- and land-based integrated time service system.  
The construction of the eLoran time service stations in Dunhuang, Korla, and Nagqu has begun, and the relevant equipment has been designed and is in production. It is expected to be in operation in 2026.  
With the construction of the system, the eLoran system faces possible challenges that need to be paid attention. The number of users is smaller than that of GNSS, and the price for eLoran users is higher than that of GNSS receivers. These may hinder the development of eLoran in China.