When using Turtles and sending them to locations, some more advanced users prefer to use GPS Towers instead of basic commands like 'go forwards'.
GPS Towers should be 4 computers each with a modem, to triangulate and verify. The higher up a tower is, the wider radius you can send a turtle. When building a GPS Tower between the Y coordinates of 70 and 80, You will need a tower about every 50 blocks or the turtle will lose it's signal.
When writing Turtle programs like Excavating and Tunneling, You may prefer to write your own scripts. You can use this to say where to tunnel to.
tunnel 130 40 1025
If coded like intended, the turtle would tunnel from its current position to the coordinates specified in the command, Being X of 130, Y of 40 and Z of 1025.
Note: When coding GPS Towers, please refer to the GPS API.