The study on improving precision of location by GPS handset;

This thesis narrated the compendious calculation process and the requirements of coordinate system transformation for GPS handset; and explained the method to take that calculates transformation parameters of the coordinate from WGS84 system into 1954 coordinate system as example.

The method that using a portable GPS receiver to locate single site statically in four days is applied in the paper.

The coordinate in WGS-84 system can be determined by mobile GPS conveniently and quickly.

The paper expounds the function and character of hand GPS through using the navigating type GPS315 of American Magellan Company as an example,and analyses its setting accuracy and its typical application instances in electric power engineering,as well as proposes some problems which should be noticed in hand GPS application.

Determination of the Tri-parameters of Portable GPS;

This paper introduces the character of portable GPS,and analyses its applying methods and results in engineering.

The absolutely-fixed position of CE solo point with Mobile Mapper by the instrument of portable GPS can satisfy the filling of the geological maps and geological engineering prospection over plains, hill areas, high mountain areas and other areas without blocks.

To solve the difficulty of replacement for fixed sample plots and the lower precision for fixed sample tree mensuration in the system of national forest resources continual inventory,the precision of inventory can be improved using portable GPS in the position of fixed sample plots,using total station to mensurate the height of fixed trees and using compass in the replacement of fixed trees.

Experimentation indicated that external accordant positioning accuracy of some portable GPS is rather too low.