中文摘要：

从GPS基本观测模型出发,给出并推导了分离相位小数偏差求解非差整数模糊度的精密单点定位数学模型和算法.利用少量IGS跟踪站组成服务端观测网计算未检校的相位小数偏差改正信息,用于改正用户端接收机的相位观测值,实现了固定非差整数模糊度的快速精密单点定位与定轨.试验结果表明：利用30min的地面动态或静态观测数据进行精密单点定位,非差模糊度固定成整数后,其定位结果较PPP浮点解有明显改善,水平方向提高了近一个数量级,可达到1cm甚至毫米级的精度;高程方向与对流层延迟解算精度也改善了20%～60%.与浮点解相比,固定解能显著改善PPP的定轨精度,仅用15min的短弧段观测数据,切向与法向的定轨精度可达到1cm左右;径向方向为3～5cm左右,较浮点解定轨精度改善了50%～70%.因此,固定非差整数模糊度后的PPP能够满足毫米至厘米级的快速精密定位和定轨的要求,这在GPS（准）实时应用与服务中具有很好的应用前景.

英文摘要：

In this paper,we give the basic mathematical model of GPS observations.The primary cause of the zero-difference ambiguity which cannot be fixed to integer in the standard PPP model is analyzed.Then,the FBI（Fractional Bias Isolating） model and method for zero-difference integer ambiguity resolution is proposed and developed.The experiment results showed that： Using the observations from sparse IGS tracking stations that space up to thousands of kilometers,the estimated UFOs（Uncalibrated Fractional Offsets） can provide a reliable PPP service with zero-difference integer ambiguity resolution for the user stations which are located in the network and thousands of kilometers away outside the server observation network.With 30-minute observation,PPP fixed solution can be realized with mm level accuracy in horizontal and cm level in height.Compared with traditional float solution,horizontal positioning accuracy is improved by about an order of magnitude,height improved by about 50%~60%,ZPD（Zenith Path Delay） also improved by 20%~30%.Meanwhile,the precise orbit determination accuracy is improved by fixed solution significantly.With only 15-minute observational data,the accuracy of about 1 cm in normal and cross,3~5 cm in radial can be achieved.It can meet the demand of mm~cm level rapid（near real time） precise positioning and LEO orbit determination.