Nice!
The GPs, pressure sensor and formfactor are the same for V3 and V4.
Here are the major changes;
+The IMU is different.V4 has a better quality IMU, but most people will not notice.
The big difference is faster output rate (6,664 times a second) for the gyro and accelerometer.
+V4 also has QWIIC connectors
+You can now communicate with the GPS module via i2c, you need to solder some jumpers to do so. this method doesn’t work with GPSD and is for advance users
+v4 includes a led for power
+v4 also include level shifters, which means you can connect it directly to a 5v device (e.g. Arduino)
Mark --OzzMaker.com --
