GPS module(GMS-U1LP) setup help
All four pins are Ground, and all four pins should be connected to your circuit ground.

It may work if you leave some of the ground connections floating, but you may have reliability issues.

That GPS module does not have separate ground domains. Basically, to reduce the impedance of the ground connection, and possibly for reliability issues, they are using multiple connections from the same ground.

It is in-fact likely that if you use an ohmmeter to measure the resistance between she separate ground connections, you will find they are coupled together within the GPS module as well. You should still ground them all, however.