The most common and simple software calculation done is the Lumen Method.
This type of program is usually straightforward. The inputs required include
initial lamp lumens, light loss factor, area or roadway dimensions and luminaire
photometric data or CU. The user must also enter either the number of luminaires
or the desired maintained footcandle level. The software then calculates the
unknown value, either number of luminaires or footcandles.
Many fixture manufacturers have their own software with the photometric data on their fixtures. The user simply chooses the fixture, and the computer can calculate the CU from the photometric database. This software calculation is most useful for inexperienced designers. The result of this number and wattage of fixtures is a good starting point for using point by point software.
