(Shown at left above, with a Locosys LS20033 GPS module for size comparison)
ArduPilot is designed to use the solid and reliable EM406 GPS module, which is a 5v, 1Hz device that works well under most conditions. But if you want more precise navigation, you may want to upgrade to the 5Hz Locosys module
that Dean Goedde is using with AttoPilot. That's a 3.3v module, so you can't just plug it into the ArduPilot board. Instead, Jordi has designed a special daughterboard that does the following:
--Converts ArduPilot's 5v power to 3.3v power
--Provides a EM406 connector, so it's a direct plug-in replacement for the EM406
--Provides a break-out connector so you can add a wireless modem, such as a Zigbee.
We may release this as a pre-made product, but in the meantime you can make your own.
Buy the board from BatchPCB here
Eagle files (schematic and PCB) are here.