澳大利亚RIA电子公司研制成一种袖珍仪器,在它的存储器中贮存有地图,同时能确定自己的位置精确到几十米,因此能形象直观地告诉旅游者现在处在什么地方,以多快速度向什么地方运动。为了测定方位,该仪器利用由24颗美国军事导航卫星组成的系统,计算表明在任何地点和在任何时间要求在地平线以上至少要有4颗导航卫星。为了测定坐标,仪器需要 Australian RIA Electronics has developed a pocket-sized instrument that stores maps in its memory and can determine its location to tens of meters accurately, so that it can vividly tell tourists where they are now and how fast What place to exercise. To determine the bearing, the instrument uses a system of 24 United States military satellite satellites and calculations indicate that at least 4 navigation satellites above the horizon are required at any location and at any time. In order to determine the coordinates, the instrument needs