Location

local X, Y, Z, O
local North, East, South, West = 0, 1, 2, 3

function forward()
  while not turtle.forward() do
    while not turtle.dig() do
      GPSup()
    end
  end
end

function locate()
  X, Y2, Z = gps.locate()
  forward()
  X2, Y, Z2 = gps.locate()
  if X2>X then O = East end
  if X2<X then O = West end
  if Z2>Z then O = South end
  if Z2<Z then O = North end
  turtle.back()
  return X, Y, Z, O
end

function GPSforward()
  if O == East then X = X+1 end
  if O == West then X = X-1 end
  if O == North then Z = Z-1 end
  if O == South then Z = Z+1 end
  forward()
  end
function GPSturn(Direction)
  while Direction~=O do
    turtle.turnRight()
    O = O + 1
    if O == 4 then O = 0 end
  end
end
function GPSup()
  while not turtle.up() do
    turtle.digUp()
  end
  Y = Y + 1
end
function GPSdown()
  while not turtle.down() do
    turtle.digDown()
  end
  Y = Y - 1
end