def add_deviation(self, dev, td=None):
        """
        Add a deviation survey to this instance, and try to compute a position
        log from it.
        """
        self.deviation = dev
        try:
            self.compute_position_log(td=td)
        except:
            self.position = None
        return
def add_deviation ( self , dev , td = None ) : self . deviation = dev try : self . compute_position_log ( td = td ) except : self . position = None return
Add a deviation survey to this instance, and try to compute a position
        log from it.