1. Department of Land Surveying and Geo-Informatics, The Hong Kong Polytechnic University, Hong Kong
2. Department of Geoinformatics & Surveying, University of Nigeria, Nsukka, Nigeria
3. Geodesy Research Laboratory, National Institute of Cartography, Yaoundé, Cameroon
4. Department of Physics, University of Yaoundé 1, Yaoundé, Cameroon