Solid angle of its faces is one-sixth of that, or sr. Solid angles can also be measured in square degrees (1 sr = () square degrees), in square minutes and square seconds, or in fractions of the sphere (1 sr = fractional area), also known as spat (1 sp = 4 sr). In spherical coordinates there is a formula for the differential, where is the colatitude (angle from the North pole) and is the longitude. The solid angle for an arbitrary oriented surface S subtended at a point P is equal to the solid angle of the projection of the surface S
Volume Area Dihedral Angle Reporter is calculated by dividing a given residue’s observed accessible surface areas by the calculated accessible surface areas for that residue in an extended Gly-Xaa-Gly tripeptide (where Xaa is the residue of interest). VADAR reports accessible surface are values both for the entire amino acid residue and for the amino acid side chains. The accessible surface areas is also calculated for charged atoms (N, O), polar (N, O, S) atoms and for non-polar atoms (C). This information can be used to calculate charged, polar and non-polar surface area. Accessible surface areas measurements/estimates are particularly useful in protein structure assessment, protein structure