Spherical Coordinates — from Wolfram MathWorld
theta to be the azimuthal angle in the xy-plane from the x-axis with 0<=theta<2pi (denoted lambda when referred to as the longitude)
phi to be the polar angle (also known as the zenith angle and colatitude, with phi=90 degrees-delta where delta is the latitude) from the positive z-axis with 0<=phi<=pi
r to be distance (radius) from a point to the origin.