Hi Arthur,
Sorry for late reply. Thank you for providing the link. The PMTK documentation helps a lot. The GPS performance improve a lot after reconfiguration.
Best Regard,
Jack Lu
For those who have similar problem, the PMTK can help improve the PmodGPS sensor, by enabled different mode. Also, you can use this to write the EPO file, to improve the oribt prediction. It would be a little better than build-in EASY mode. It is important to remember to write the initial time and location. As far as the RTCM, I think it would be difficult to acquire any info to enable this function. According to my trace, the company, Gtop GPS division, has been sold to Sierra. But Sierra cannot provide any info for how to enable it.
If you have the need to improve the accuracy, I would suggest to take a look at other GNSS module. Remember paying attention to the mode supported by the GNSS you selected. Some of them only support two system at same time. However, according to my experiment, smartphone build-in GNSS block mostly support 4 system simultaneously. Also, if your application is ASIC like me, I would suggest to use serial communication between the FPGA and GNSS modules. According to my experience, most GNSS modules at least support this interface.
Hope this will helps others.