In order to obtain the highest achievable accuracy for your submitted observation file given our GAPS PPP algorithm, please consider the following:
For PPP, there is one general rule of thumb: the longer the observation period, the more precise the processing results will be. When considering the typical convergence periods for the PPP technique (see below section), we recommend observation periods of at least 2-3 hours in order to achieve centimetre-level positional solutions in static mode.
Another consideration in file submission to GAPS is product latency. If centimetre-level positional solutions are desired, we highly recommend that you wait for the availability of the IGS Rapid orbit and clock solutions at a minimum. These products are typically available within 17-41 hours of the observation date. While we do provide solutions using the IGS Ultra-rapid product, users should certainly expect a degradation in the positional solution. Another concern in product selection should be the observation period. As the Ultra-rapid product provides satellite clock corrections at a rate of just 15 minutes, a 1-hour long observation file will only process 4 periods of observations! Certainly, one can expect the estimated solution to be fairly unreasonable.
As previously stated, the convergence period of the GAPS' PPP algorithm should be a factor when considering the minimal observation period. In most cases, GAPS requires a minimum of 2-3 hours of observations in order to converge to the centimetre level of a positional solution. Other considerations for the convergence period include the observation and/or processing rate. If the IGS 30-second product is utilized and the user-submitted RINEX file was logged at a 30-second rate, convergence time will be minimized. On the other hand, if the Ultra-rapid product is utilized (15-minute satellite clock corrections) and a user-submitted RINEX file was logged at a 5-minute rate, the user should expect a fairly large degradation in the final solution.
For more information or any inquiries, please contact: GAPS Development Team (gaps [at] unb.ca)