The direction of magnetic field at any location on the earth’s surface is commonly specified in terms of

The direction of the Earth's magnetic field at any specific location is defined by two angular parameters: magnetic declination and magnetic inclination. Magnetic declination is the horizontal angle between the magnetic north (the direction a compass needle points) and the true geographic north [2]. Magnetic inclination, also known as magnetic dip, is the vertical angle that the magnetic field lines make with the horizontal plane of the Earth's surface [1]. While the total intensity of the field is described by various components including the horizontal intensity, the specific parameters used to specify the 'direction' of the field vector are declination and inclination [2]. Together, these two angles provide the three-dimensional orientation of the magnetic field relative to the local geographic coordinate system at any point on the Earth's surface.

Sources

1. [2] Physical Geography by PMF IAS, Manjunath Thamminidi, PMF IAS (1st ed.) > Chapter 5: Earths Magnetic Field (Geomagnetic Field) > Magnetic Declination > p. 76
2. [1] Physical Geography by PMF IAS, Manjunath Thamminidi, PMF IAS (1st ed.) > Chapter 5: Earths Magnetic Field (Geomagnetic Field) > Magnetic Inclination or Magnetic Dip or Dip Angle > p. 77