These sound like spherical coordinates. How to convert to Euclidean coordinates depends on whether you are using a right- or left-hand coordinate system and where you put the axes, but the basic ideas are readily available with an internet search. Here is the Wikipedia page: Spherical coordinate system - Wikipedia, the free encyclopedia If you use the standard spherical coordinate system, the formulas are You might want to let z --> -z if you are measuring under the surface of the earth. If you are using another system, you might need to change sines and cosines around. Check the formulas with limiting cases such as "straight down" and "on the surface."
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