In the spherical coordinate system, the three line segment elements along the direction of the base vector are:

dl(r)=dr，dl(θ)=rdθ，dl(φ)=rsinθdφ

The bin area of spherical coordinates is:

dS=dl(θ)* dl(φ)=r^2*sinθdθdφ

The volume of the volume element is:

dv=dl(r)*dl(θ)*dl(φ)=r^2*sinθdrdθdφ