A Waldram diagram is an aid to the calculation of sky factors.
The axes are arranged so that the contribution to the illumination
at a point from an overcast sky is proportional to the corresponding
area on the diagram. So if one determines the area of unobstructed
sky on the diagram, this area, expressed as a fraction of the total
diagram area gives the sky
factor at the point.
The two Waldram Diagrams on the right show an example of the amount
of sky visible from a window. The top diagram shows an existing
neighbouring building in green, the building being developed is
shown in red on the bottom diagram.
It is apparent from the diagrams that both existing and proposed
buildings produce a similar vertical angular obstruction of about
65 degrees. The reduction in visible sky is due to the proposals
increased width. Moreover this increase in massing is predominantly
to the right hand side of the diagram.