what is the angle between the magnetic field vector and the horizon of the place of interest.

To answer this question, you would need to have specific information about the location and the magnetic field at that location. However, here are the general steps you would take to find the angle between the magnetic field vector and the horizon:

1. Determine the location's geographic coordinates (latitude and longitude).
2. Use these coordinates to find the magnetic field vector at this location. This can be done using a magnetic field calculator or model, which are available online.
3. The magnetic field vector will have three components: one pointing north, one pointing east, and one pointing down. The angle between the magnetic field vector and the horizon (which is a horizontal plane) is the same as the angle between the magnetic field vector and the vertical direction (down).
4. This angle can be calculated using the arctangent of the ratio of the horizontal components (north and east) to the vertical component. In mathematical terms, if Bn, Be, and Bd are the north, east, and down components of the magnetic field vector, respectively, then the angle θ is given by θ = arctan(sqrt(Bn^2 + Be^2) / Bd).
5. Make sure to convert this angle from radians to degrees if your calculator gives the result in radians.

Remember, this is a simplified explanation. The Earth's magnetic field is complex and can vary depending on factors like solar activity and the Earth's internal processes.