1. Department of Mathematical Sciences and Technology, Norwegian University of Life Sciences, P.O. Box 5003IMT, 1432 Aas, Norway
2. Faculty of Surveying and Mapping, Hanoi University of Mining and Geology, Dong Ngac, Tu Liem, Hanoi, Vietnam
3. Department of Civil Engineering, Spatial and Numerical Modelling Research Group, Faculty of Engineering, Universiti Putra Malaysia, Selangor, 43400 Serdang, Malaysia