Besides daily solutions from GPS double difference processing, sub-daily solutions could provide a higher resolution of coordinates evolution, which means more detailed information about the motion of study target. Sub-daily solutions are 3D coordinates computed out of GPS data with observational duration less than one day. The observational duration could be as short as several hours or even several minutes which will come to the concept of near real-time solutions.
The challenges of sub-daily solutions are:
To overcome the challenges mentioned above, better understanding and modeling of effects from ionospheric delay, tropospheric delay, multi-path, antenna phase center variations (PCV) and other possible noises must be assessed further.