GPS Module not sending data on Puck.js

Ahh - thanks! I just modified the posts above to use console.log("DATA", data); and not console.log("DATA"+ data);. It's just the way JS handles converting Objects to Strings.

Why is it important to connect the ground of the GPS module to the ground of the puck?

It's just a general electrical thing. Voltage is relative - imagine you're trying to measure the voltage on a battery - you need to connect both ends of it to the volt meter - just one isn't enough.

So in pretty much all digital electronics, to make things easier you just connect all the grounds together, so that always sorts out one side of the connection and then you just worry about the signal wires.