PaulS:
And how much measurings (both Gyro and GPS) would a 10gb SD card would be able to save.
How many buckets can my barrel hold? If you want to store one reading a day, you could probably store a couple of centuries worth of readings. Store more often and the duration goes down.
How you store the data matters. How much data you store matters. How often you store the data matters. In which file(s) you store the data matters.
2 readings a day, .text file, a line where's written time and coordinates.