time stamp can be added to the header to maintain continuous timing information if data loss occurs in the packetized interface as well as to keep timing synchronization between gps and glonass signals each combined packet of data shown in fig4 contains a gps field 404 the packet also contains several glonass fields 406 1 to 406 n assuming there are u2018 n u2019 glonass channels each glonass field corresponding to a glonass channel there is also a header field 402 containing identification information for each packet being the same format as the legacy gps data the gps signal in the combined packet is real sampled with 2 bits quantization the data in gps field is formatted as shown in fig5 in fig5 a time axis is shown as 502 along which the in phase i samples 506 1 to 506 n are arranged each sample 506 contains several components 508 each having corresponding sign magnitude sgn mag combinations 510 table 510 shows corresponding mapped values for the sgn mag combinations 00 01 10 and 11 the data in each of the glonass channel fields is formatted as shown in fig6 in fig6 a time axis is shown as 602 along which the in phase i samples 606 a and quadrature phase.