libri" size="3">We applied the non-orthogonal grid finite difference time domain libri; mso-ascii-theme-font: minor-latin; mso-fareast-font-family: 宋体; mso-fareast-theme-font: minor-fareast; mso-hansi-font-family: calibri; mso-hansi-theme-font: minor-latin">(libri" size="3">FDTDlibri; mso-ascii-theme-font: minor-latin; mso-fareast-font-family: 宋体; mso-fareast-theme-font: minor-fareast; mso-hansi-font-family: calibri; mso-hansi-theme-font: minor-latin">)libri" size="3"> method to the 3D Transient electromagnetics libri; mso-ascii-theme-font: minor-latin; mso-fareast-font-family: 宋体; mso-fareast-theme-font: minor-fareast; mso-hansi-font-family: calibri; mso-hansi-theme-font: minor-latin">(libri" size="3">TEMlibri; mso-ascii-theme-font: minor-latin; mso-fareast-font-family: 宋体; mso-fareast-theme-font: minor-fareast; mso-hansi-font-family: calibri; mso-hansi-theme-font: minor-latin">)libri" size="3"> simulation with topography. We also presented a modified non-orthogonal grid FDTD method taking into account a weighted projection technique. The numerical simulation results based on various topographical models indicate that the topographical parameters such as the depth, width and source distance could affect the simulated TEM field.