Solar activity is subject to an approximately 11-year cycle, with the next solar maximum predicted for the year 2025. According to observations by the Space Weather Prediction Center (https://www.spaceweather.gov/products/solar-cycle-progression), solar activity in the current cycle is already significantly stronger than predicted at the beginning of 2023 and is already at the solar maximum level experienced during the last solar cycle.It can be assumed this increase will continue and that observations reliant on GNSS correction services will be subject to effects and disturbances during this peak portion of the cycle.
Impact on RTK measurement performance
Solar activity represents one of the main sources of errors on GNSS measurements. Normal solar radiation and activity causes an ionization of the particles in the higher layers of the atmosphere (ionosphere) and this ionization affects the propagation of satellite signals.Additionally, discrete solar events, e.g. solar storms may cause strong fluctuations in the Earth's magnetic field, which also affect the propagation and quality of the satellite signals.In principle, GNSS correction services such as HxGN SmartNet use a network of GNSS reference stations and advanced modeling techniques to estimate the effects of the above-mentioned ionospheric influences and attempt to mitigate the effects of these errors on positioning in the field.
Due to a high solar activity, however, these influences are amplified making modeling less precise resulting in larger distance-dependent residual in correction service outputs.
This can manifest itself during positioning in the field by:
- extended fixing times at the RTK rover (sometimes several minutes)
- a degradation of the positioning accuracy (even with successful fixing)
Solar activity and the corresponding effects on the measurement can vary strongly from day to day, at different times during the day and at different field locations.The influence of these effects occur more frequently in the afternoon as the ionospheric activity begins to peak.
Recommendations for positioning in the field
- Adhere to good surveying practices
- Perform multiple observations, over multiple epochs with a 45+ min separation of time between observations
- Perform hybrid measurements utilizing both GNSS and terrestrial technologies
- Perform observations utilizing many satellite systems and frequencies as possible, this can further mitigate the effect, but not eliminate it
- Perform observations utilizing the most current firmware for the RTK rover