确定重力场的主要边值问题从数学上看都是线性问题，其原型都是某个关于重力场的非线性问题，在得到这些常用的线性化模型时都舍去了所谓高阶小量的非线性误差。另外利用这些线性化的边值问题建立的重力场模型的阶次也越来越高，例如：EGM08模型已经达到了2160的完整阶次。如此就产生了这样的理论问题：线性化的边值问题到底能还原出多大阶次的重力场模型呢？如果线性化问题解算重力场模型的阶次有上限，那么如何估算该上限呢？此外就是上限以后的阶次又该如何确定呢？.项目的目的就是试图回答上述问题。研究工作将从各类线性化边值问题的原型（非线性问题）出发，来得到线性化问题与相应重力场模型阶次之间的关系，其中核心部分就是开展所谓非线性误差项的球谐分析研究。项目的完成对于完善重力场理论以及建立高分辨率的重力场模型有着积极的作用。

It is well known that main geodetic boundary value problems (BVP) are linearized from some non-linear ones. On the other hand, the established models of the gravity field reach to very high degree/order, e.g., EGM08 model has reached to 2160 degree/order completely. Since some so-called high order errors are neglected in deriving the linearized BVPs, it is naturally to ask how many degree/order in the models of the gravity field can be solved from the BVPs? Our research work is based on such problems.. We will study the non-linear problems and try to solve them by means of spherical harmonic analysis. Then obtain the relations between BVPs and the degree/order of the gravity field solved by them. Our study is very helpful for high accurate models of the gravity field.