Friday, July 22, 2011

New online IES to EULUMDAT Converter now also handles Type B photometry

A new version of the free online IES to EULUMDAT Converter was published today at

We added the conversion of Type B photometry IES files to EULUMDAT to the existing conversion of Type C files.

Some background theory

The photometric intensity distribution in EULUMDAT files is similar to that a Type C IES file. The center of beam is straight down (or up) and there are vertical (IES: lateral) planes rotating around this central down axis. In each vertical (IES: lateral) plane there are a number of vertical angles. For more info see AGI32 website.

Trigonometric conversions

To determine the intensity at a pair of the C and γ angles, we need to interpolate at a corresponding pair of B and β angles. The corresponding B and β angles can be found using these formulas:

tan B = cos C * tan γ

sin β = sin C * sin γ

We added some extra logic to handle the determination of the right quadrant.

Interpolation used

Interpolation is done using standard lagrange over 3 planes and then over the 3 resulting points.

More info

See this book for more details.