Research On The ASF Correcting Of Long-wave Time Server

With the fast development of satellite navigation system, the GPS of the USA has beenwidely used in all fields, and the COMPASS of our nation would soon accomplish the wholesystem. The Loran-C time server is an important timing server of our country, which comparedwith satellite navigation system, although whose transmission power, the stability of the signalpropagation, less susceptible to interference, but its precision is lower. To match the increasingprecision demand of communication and industrial automation etc, it is necessary to improve theprecision of The Loran-C time server. As the ASF is the key factor influencing the Loran-C timeserver timing precision, research on the ASF timing delay correction thus has important practicalsignificance, The thorough research on the ASF timing delay correction had been conducted inThe Loran-C time server, the main work in this paper is as follows.1. Based on the statement of the long-wave timing and the main factors affecting ASFtiming delay correction, some factors which is ignored on ASF calculation were pointed out.These factors are the basis of the ASF correction and introducing new thoughts.2. The calculation of the long-wave timing delay and the principle of Millington algorithmcalculating the ASF delay were introduced. Through the analysis of Millington’s method tocalculate the ASF delay, design experiment, collection data, analysis the experimental results, theerrors of the map location, the ground equivalent conductivity and the ground equivalentconductivity region segmentation on ASF time delay calculation appeared. Moreover, somemethods to avid the errors mentioned were put forward,such as adopting Google Maps,real-time factors for acquisition and transition region segmentation, and the preliminary researchon these principles and algorithms.3. The practical measurement method on ASF time delay and the principle of interpolationmethod in modifying ASF delay were stated. The ASF database of the North China Plain wasestablished by the practical measurement method and the exact ASF correction of the databaseby the bilinear interpolation was achieved. On this basis, a nationwide ASF database wasinitially established, and through a number of observational verification, its reliability could berealized, then according the data of these observant points, analysis the problems of the database.4. The ARM Cortex-M3kernel system architecture and the chip peripherals of STM32basedon this kernel were introduced. According to the requirements of the ASF correction, thecorrection of the terminal design function and hardware structure. Because of the complexity ofthe real-time factors and randomness, and the experiment condition limit, no relevant of measured data support real-time factor mathematical model, can’t further thorough. The processand functions of software were mainly analyzed, and a nationwide non-real time bilinearinterpolation ASF delay correction function was realized on the hardware.