Lighting & Spectrum

Sun Path Viewer

Visualize solar elevation, azimuth, and shading windows over the year.

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What it does

A sun path viewer that plots solar altitude and azimuth hour by hour for a chosen site and date. It also estimates monthly natural DLI and the supplemental PPFD needed to reach a crop DLI target.

When to use it

Use it for greenhouse orientation, glazing and seasonal shading decisions, and to see which months fall below a target DLI. It is a design visualization and engineering estimate, not a survey instrument.

How it calculates

Solar altitude and azimuth come from NOAA simplified solar-position equations, sampled hourly in the site's local time.
Clear-sky PPFD uses the Kasten-Young air mass with Meinel-style atmospheric transmission. It is integrated every 15 minutes on the 15th of each month.
Natural DLI = clear-sky DLI × glazing PAR transmittance × clear-sky fraction
Required PPFD = DLI deficit × 1,000,000 ÷ (supplemental photoperiod × 3600). Annual supplemental light assumes 30 days per month.

What you enter

Site location(address, ZIP, city or lat, lon)
Date
Glazing / cover(% PAR)
Custom transmittance(%)
Crop target DLI(mol/m²/day)
Custom target(mol/m²/day)
Clear-sky fraction(%)
Supplemental photoperiod(hours/day)

What you get

Altitude vs Time(°)
Azimuth Polar Plot(°)
Monthly natural DLI(mol/m²/day)
Peak month and worst month(mol/m²/day)
Supplemental needed(months of 12)
Worst-month deficit(mol/m²/day)
Required PPFD, worst month(µmol/m²/s)
Annual supplemental(mol/m²/yr)

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