Sometimes the dead-reckoning code doesn't work. The current implementation relies on the Slocum glider x_dr_state variable to properly identify the dive state e.g. whether the glider is a the surface or about to dive. This information is used to identify the various phases of recording the GPS signal at the surface and estimate surface drift which is used to correct the glider compass recorded m_lon and m_lat variables.
If the code doesn't work the toolbox will still complete and save the netcdf trajectory file but there won't be any data in the lon_qc and lat_qc variables.
Sometimes the dead-reckoning code doesn't work. The current implementation relies on the Slocum glider
x_dr_statevariable to properly identify the dive state e.g. whether the glider is a the surface or about to dive. This information is used to identify the various phases of recording the GPS signal at the surface and estimate surface drift which is used to correct the glider compass recordedm_lonandm_latvariables.If the code doesn't work the toolbox will still complete and save the netcdf trajectory file but there won't be any data in the
lon_qcandlat_qcvariables.The dead reckoning correction code can be found here: https://github.com/OceanGNS/PGPT/blob/77ee28944e5a7d493f5b0b2dfb0406ef02548baf/scripts/gliderfuncs.py#L277
The theory for how the code works is explained here and also shown in the attached image: https://oceangliderscommunity.github.io/DepthAverageCurrents_SOP/sections/DACs_rtqc.html