中文摘要：

高程基准是大地测量参考框架的重要组成部分，也是数字地球基础框架的重要内容．但目前各个国家或地区使用的大多是局部高程基准，这严重影响了地球信息数据的全球共享机制．本文利用高程基准与重力位之间的关系，推导了不同高程系统之间的严密位差计算公式和近似计算公式．该理论将为我国和全球高程基准的统一提供理论支持．

英文摘要：

Height data is not only a very important part of geodetic reference system, but also the important content of Digital Earth. However, present height datums are mostly local height data, which have seriously affected global information sharing of Earth data. In the paper, using the relationship between height data and gravity potential, we deduce a group of formulas on computing the potential differences. The formulas are the basis of unification of global height data.