Calculating Light Level at a Point

1. Nov 15, 2007

cmdrico7812

I haven't used my high school physics education in a really long time but I need to here at work for a very simple problem. I am an urban planner and we deal with lighting regulations a lot. I am trying to calculate the light level (in footcandles) at a given point. I am using the following general equation:

[footcandles] = [light level in lumens of the source light] / [direct distance from point to light source]^2

All I need to know is what units do I use to measure the distance? Meters, feet, inches? Would I measure the distance in feet since my light unit is footcandles? I know the standard scientific measurement unit is meters or some derivation there of, but I wanted to ask here just to be sure. Many thanks in advance.

Eric

Last edited: Nov 15, 2007
2. Nov 15, 2007

marcusl

Feet. A footcandle is defined in units of lumens/ft^2.