Midtown NYC zoning requires a daylight study to maintain sufficient sky exposure at street level.
One of the two evaluation methods is called the Daylight Evaluation Method.
Waldram diagrams need to be plotted at different locations around the lot and a score is calculated based on the coverage of "squares" by the building silhouette.
The construction of the diagram and the calculation of the score is very complex if done by hand but clearly explained in the NYC zoning code.

I created a Grasshopper definition that automatically executes the process and provides the score to allow fast iterations through options.

Please reach out to with any question.