VERIPOS Standard Plus
VERIPOS Standard Plus is a dual frequency service designed to help mitigate the effects of heightened ionospheric activity along the geomagnetic equator.
The ionospheric activity can have a detrimental effect on the positioning performance of VERIPOS Standard due to inaccuracies of the broadcast ionospheric model.
Using observations on both L1 and L2 frequencies allows the mitigation of the position errors by calculating, instead of modelling, the ionospheric delays in each satellite signal, and thereafter removing its effects. In addition to the normal pseudo-range corrections transmitted in the Standard service, measured ionospheric delay information for each satellite at each reference station is also broadcast.
There are two symptoms of ionospheric activity on DGPS. Firstly, position errors caused by failure of the differential process to cancel the effects of ionospheric delays. Secondly, scintillation – which causes rapid fluctuations in the phase and amplitude of the satellite signal as it passes through the ionosphere.
This information, which is available in RTCM format, is combined with locally measured values to give a position, free from the effects of the ionosphere. As the ionosphere is changing relatively slowly, a fast update rate for the corrections is not required.