I am looking to analyze outside lighting data and its implications on human health regionally, but I can't seem to find a ubiquitous database that contains outside lux illumination data throughout the continental US. This is essential to my study and seems to be measurable, but virtually nonexistent on each climactic database I request from.

Any help is appreciated,

Thank you.

  • $\begingroup$ you will not find it in lux here but you might be able to convert it from this site : timeanddate.com $\endgroup$ Commented Nov 26, 2018 at 5:37
  • $\begingroup$ simply input your location in sunrise and sunset and you will get the graph telling the light level during the day/night. $\endgroup$ Commented Nov 26, 2018 at 5:53
  • $\begingroup$ I am looking for the source of this data. not how to convert specific energy quantities. Do either of you have access to this data or have any leads on where it might be? $\endgroup$
    – user14379
    Commented Nov 27, 2018 at 2:18
  • $\begingroup$ @ZacheryUtt Are you looking for natural (sun) or artificial light (street lamps)? Probably the latter? $\endgroup$ Commented Nov 29, 2018 at 10:26
  • $\begingroup$ As I understand it, you're asking for a dataset that shows how bright it is outside during daylight hours for varying locations.... and not just based upon ideal amounts of sunlight but weather conditions? $\endgroup$ Commented Dec 11, 2018 at 9:57

1 Answer 1


One direction to look in might be the various GIS systems that exist to forecast the amount of light that will reach photovoltaic (solar panel) installations. I don't know about the US, but I would be very surprised if there isn't one - try googling for "PV GIS" or similar.

Now, that will give you insolation (illuminance) in W/m2. It may be further broken down into direct and indirect insolation (that's direct sunlight and diffuse light from the sky or clouds), or it may be a single global figure.

Since you're after the information in lux rather than W/m2, you'll need to convert it. This will necessarily be an approximate process, but so long as you don't need very high accuracy it should be quite doable. Lux is at base a measurement of power density, just like W/m2, but it's modified by a frequency-dependent function that represents the sensitivity of human vision. So you'll need to assume a spectrum for the sunlight, and then apply the conversion curve (which is an international standard, and hopefully available on the internet).

  • $\begingroup$ From what I've seen, the quick work around is to assume monochromatic light with a wavelength of 555 nm, which is a green coloured wavelength the human eye is most sensitive to. At that wavelength 1 lumen = 1/683 W. $\endgroup$
    – Fred
    Commented Jan 10, 2019 at 13:06
  • $\begingroup$ @Fred because that's the wavelength that the eye is the most sensitive to, assuming that all of the power is at that wavelength will give a substantial overestimate. $\endgroup$ Commented Jan 10, 2019 at 17:36

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