摘要
本文在假定小范围内大地水准面为一圆球面的前提下，探讨了土地切平面面积（即水平面积，下文同）与其对应的球面积之间的关系，以及切平面面积随高程的变化而变化的规律，指出了用土地切平面面积代替土地球面积的限度。
The paper discuss the relationship between land plane area and its sphere area, and regularity of plane area change with height on the supposition that geoid is a circular. It points out the limit of replaced land sphere area by its plane area.
