Nwilo, P., C. Okolie, J. Onyegbula, O. Abolaji, M. Orji, O. Daramola, and I. Arungwa. “Vertical Accuracy Assessment of 20-Metre SPOT DEM Using Ground Control Points from Lagos and FCT, Nigeria”. Journal of Engineering Research, Vol. 25, no. 2, July 2020, pp. 153-64, http://jer.unilag.edu.ng/article/view/997.