# How to get the solar zenith from the longitude and latitude?

I have real data of “Direct Normal Irradiation” and “Diffuse Horizontal Irradiation” and I should calculate “Global Horizontal Irradiation”. I have also longitude, latitude and elevation. Could you advise me how I can get zenith from these data, then to calculate the GHI? Many thanks,

Thus $$GHI = DHI + DNI \times cos (Z)$$ where $$Z$$ is the solar zenith angle.