<SYSTEM_TASK:>
Solve the following problem using Python, implementing the functions described below, one line at a time
<END_TASK>
<USER_TASK:>
Description:
 def interpolate(self):
 """Do the interpolation and return resulting longitudes and latitudes. """

        self.latitude = self._interp(self.lat_tiepoint)
        self.longitude = self._interp(self.lon_tiepoint)

        return self.latitude, self.longitude