[fole72]

Hi,
I would like to build a differential GPS from two standard low cost GPS modules such as the Lassen iQ or EMC-408. The system that I have in mind should work for distance between the base and the rover less than 1Km.
Theoretically, if I have understood correctly, one GPS can be configured as FIXED , positioned on a know position, and it can provide the correction information such as the RTCM message (base).
The other should be able to accept the correction message on a secondary serial port communication and compensated for the majority of the error (rover).
Put like this it looks simple but I’m not be able to figure out how extract the correction information from the GPS used as base and how configure it to do this. Assuming this is possible.
Many GPS accept the input correction information through a RTCM protocol but it seems they cannot generate it.
I have seen that there are software such as RTKLib that should perform a similar operation but when I look to the protocol accepted I cannot see anything like Sift III or TSIP protocol that are normally used on these module.
Can somebody help me or give suggestion where found application note or examples?

Thanks Andrea