Debug GPS Issues
The image as it stands is set up for use with the Adafruit Ultimate GPS hat out of the box. With the GPS hat taking the device assignment /dev/serial0.
I also have a Ubox Glonass / GPS USB stick that likes to take the assignment /dev/ttyACA0. So if you are not using the Adafruit Ultimate GPS Hat you will need to modify the GPSD configuration to match your particular device.
If you do not know what device assignment your GPS device is taking. First step is to look at the output from the lsusb command and check that the device is visible to the OS. If it is take a look output of the dmesg command and you should be able to see when the OS initialises the device and the device assignment it has been given.
From the screenshot above we can see the device is available at /dev/ttyACM0.