Lei Yan & An Li 
Mathematical and Physical Fundamentals of Navigation and Positioning with Earth’s Natural Fields [PDF ebook] 

Introduction.- The basis and theoretical model of earth gravity field navigation and positioning.- Navigation and positioning method of earth gravity field.- Fundamentals and Theoretical Models of the Geomagnetic Navigation and Positioning.

Yan Lei is now a second-level professor and doctoral supervisor at the School of Earth and Space Sciences, Peking University. He is a foreign member of the Russian Academy of Natural Sciences and the chairman of the Expert Steering Committee of the International Journal of Remote Sensing. He successively served as a director of Beijing Key Laboratory of Spatial Information Integration and 3S Engineering Application and a deputy director of Academic Committee. He has published more than 310 research papers, more than 70 have been indexed by SCI/EI data, and more than 20 invention patents have been obtained. He has published ten monographs.
Li An is a major general professor and doctoral supervisor of Navigation Engineering Department at Naval University of Engineering. He has been engaged in the teaching and research of inertial navigation system and technology for a long time and has high attainments in the fault diagnosis, damping technology, fast alignment and error correction of inertial navigation system. He has won a third prize of national invention, 10 second prizes of military (provincial) science and technology progress, 2 first prizes and 3 second prizes of military teaching achievements, and published more than 80 papers and 3 monographs.
Wanfeng Ji is an associate professor. He is now an associate professor at the Naval Aeronautical University. He has been engaged in teaching and research work in the field of ship positioning and navigation for a long time and has achieved fruitful results in ship navigation support and aircraft route planning. He has won a second prize and a third prize of military (provincial) scientific and technological progress, a third prize of military theory outstanding achievements, and published more than 30 papers and 3 monographs.
Yang Li is a doctor. He is now a lecturer in the Department of Navigation Engineering at Naval University of Engineering. He received his Doctor degree of Optics Engineering from Huazhong University of Science and Technology in 2022. He is mainly engaged in the teaching and research work of laser technology and cold atom interference gravity measurement. He has published more than 20 papers, 14 have been indexed by SCI/EI data, and 3 invention patents have been obtained.