GNSS Receiver Operation Overview - A Software-Defined GPS and Galileo Receiver: A Single-Frequency Approach - page 70

FIGURE 5.4. The basic principle of GNSS positioning. With known position of four satel-
lites SVN i and signal travel distance ρ i , the user position can be computed.

The last thing to do before making position computations is to compute pseu-
doranges. The pseudoranges are computed based on the time of transmission from
the satellite and the time of arrival at the receiver. The time of arrival is based on
the beginning of the subframe.

5.2 Computation of Position

The final task of the receiver is to compute a user position. The position is com-
puted from pseudoranges and satellite positions found from ephemeris data. Fig-
ure 5.4 gives an impression of the method of position computation using GPS.
Section 8.5 gives a detailed description of the computational algorithm.