I have an Adafruit Ultimate GPS, which cost me around £35. I did not want to risk this on my Weather Balloon and so looked for a cheaper alternative. I didn’t need a number of features on the Ultimate GPS, I just needed to get a height and location. The Ublox NEO6 can be had on eBay for about £8 and so I sent for one. It arrived in about two weeks, which is good comming from Hong Kong. The board is about the same size as the Ultimate GPS, but the ceramic antenna was bigger. I needed to solder a four pin header and I used a spot of hot glue to hold the antenna to the board.
The device is 3volts, so it needs a logic level shifter if I was going to use it with a USB FTDI adaptors. Hobbytronics sell an I2C bidirectional logic level shifter here for £3. The advantage of this board is that it has a 3.3 volt 250 mA regulator that will supply the Ublox GPS.
The logic level shifter has a 5 volt side and a 3 volt side and it is very important that you connect it the right way round. The 3 volt pin is an output pin and if you accidentally connect 5 volts to the 3 volt pin you will destroy the regulator. Connect the 5 volt pin to 5 volts on the USB adaptor and Gnd on the USB to GND on the logic level shifter. Tx and Rx on the USB adaptor are connected to SDA and SCL on the 5 volt side (it doesn’t matter which way round).
Now for the 3 volt side of the logic shifter board. Connect the 3 volts and Gnd to the Ublox GPS board. The Ublox can use either 5 volts or 3 volts as a power supply. Tx from the USB adaptor needs to connect to the Rx on the Ublox board (and Rx to Tx) so if you connected the Tx from the USB adaptor to the 5 volt SDA pin then connect the 3 volt SDA pin to the Ublox Rx pin. Connect Rx from the USB board to Ublox Tx through the SCL pins.
Once it’s all connected up plug USB adaptor into a USB socket on the Raspberry Pi. Install GPSD as shown here. The same setup can also be plugged into an Arduino without any alteration.
The Ublox GPS performed just as well as the more expensive Adafruit Ultimate GPS and acquired a lock in about the same time. Accuracy seemed to be within 2 metres in an urban location. I feel this little unit is amazing value for money.