It is important to note the sign convention for the two angles α and δ′. The deviation is measured from the vertical and is positive, whereas the dip is measured from the horizontal and is positive if it is in the same direction as the deviation and negative if the dip is opposite to the deviation. | It is important to note the sign convention for the two angles α and δ′. The deviation is measured from the vertical and is positive, whereas the dip is measured from the horizontal and is positive if it is in the same direction as the deviation and negative if the dip is opposite to the deviation. |