英语翻译Each measurement set is stored in a sub-block of the Mea

英语翻译
Each measurement set is stored in a sub-block of the MeasEpoch block.A channel configured to track only,say,GPS L1 will generate one sub-block,and a channel configured to track Galileo L1,E5 and E6 will give rise to three sub-blocks:one for each of the signals.To decrease the block size,all the measurements from a channel are referenced to one “master” measurement set.For instance,the L2 Doppler is not much different from the L1 Doppler (scaled to the L2 frequency),such that the difference is encoded,instead of the entire value.This is done by using two types of sub-blocks:the master measurement set is encoded in a long type-1 sub-block,as entire values.The other measurement sets are encoded in shorter type-2 sub-blocks,containing only the differences with the master measurements,whenever applicable.Every channel in the receiver produces one type-1 sub-block,followed or not by a number of type-2 sub-blocks depending on the available data.Every type-1 sub-block contains a field called “N2”,which gives the number of type-2 sub-blocks that are dependent on it.These dependent type-2 blocks immediately follow the type-1 block.The first sub-block is always of type 1.The total number of type-1 sub-blocks in the MeasEpoch block is given by the field called “N1”.If there are no measurements available for an epoch (due to signal obstruction for example),the N1 field is set to 0.