As ascii data are logged to serial directories in ‘raw/’ (e.g. ‘raw/ashtech’), a python thread created by UHDAS continually extracts the useful numbers from each NMEA line and appends them to the end of files in a parallel rbin directory (e.g. ‘rbin/ashtech’).
The raw instrument files are ready to be loaded into matlab using an overloaded methods read function in your path if you run radcppath.m (must specify instrument and logging program). Type “help read” for more info.
Matlab loadable files for all of the raw ascii nav messages must be created (raw binary or rbin). Each message is parsed and assigned a Unix time stamp. There is a 1:1 correspondence between the raw file name and the rbin file name.
Load into matlab using something like this
[rdata, rstruct] = read_bin(file);
e.g., for the *$GPGGA* message, the structure looks like
rstruct:
rstruct.message
rstruct.rows
{'u_dday'
'dday_frac'
'lon'
'lat'
'qual'
'hdop'
}
For an instrument like Ashtech where multiple messages are logged, there is an rbin file created for each type of data, i.e., one for the position (GGA) and one for the attitude (ATT) messages.