# 2.1 Introduction into Point Positioning

Single point positioning (SPP), also referred to as absolute positioning or point positioning, is the most basic GPS solution obtained with epoch-by-epoch least-squares estimation. For SPP, GPS provides two levels of services, the Standard Positioning Service (SPS) with the access for civilian users and the Precise Positioning Service (PPS) with the access for the authorized users. Traditionally, in SPS, only the L1 C/A-code was available. As part of the modernization efforts, civilians would now gain access to the L2 C/A-code. The achievable real-time SPS 3D positioning accuracy is ~ 10 m at the 95% confidence level. The SPS model is presented in equation (2.1).

$$E = mc^2 \label{eq3}\tag{3}$$

$$E = a_{12} + m_{12}c^2$$

blah blah blah, reference equation (3)

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