j2me本地文件存取实例，GPS项目中本地地图读取模块。-j2me instance of a local file access, GPS projects, read the local map module.

1. what kind of noise/errors/uncertainties/unmodeled things affect the GPS precision : AS, SA, orbits, clocks, ionosphere, troposphere, antenna phase centers, centering (tribrachs), etc... 2. how do we evaluate GPS uncertainties ? (difference b