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KJ and lux

  1. Jul 28, 2008 #1
    Hello,

    I'm working on a GIS modeling project where I'm trying to predict dragonfly habitat. I have collected my field data using a hand-held meter that measures illuminance in lux. I am wanting to incorporate some other spatial data I derived using a digital elevation model which shows solar radiation in kJ/m^2.

    Is there a way to convert the lux values into kJ/m^2? It's not really necessary for my analysis, but yet would be useful in comparison.

    I'm thinking that the two measurements, even if not able to convert can be discussed in the same regard as both are measure of sunlight/energy which is a factor in the dragonfly habitat.

    Any insight or suggestions are greatly appreciated.

    Thank you,
    Darcy
     
  2. jcsd
  3. Jul 28, 2008 #2

    mgb_phys

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    Not directly, you have to make assumptions about the wavelength range and source.
    Lux is lumens/m^2, Lumen is the power on the surface but adjusted for the response of the eye.
    Sunlight is about 90lumens/watt
     
  4. Jul 28, 2008 #3
    ok, Thank you.
     
  5. Jul 28, 2008 #4

    mgb_phys

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    I don't think I explained that very well.
    Lux is the unit of ilumination = power / area
    So 1 lux is 1 lumen / m^2, and daylight is about 30,000-100,000 lux or 30-100 Kl/m^2

    Lumens are normally used with artificual light sources to compare how much light you get out for a certain power in - thats because you can't compare the light output of a 1Watt LED and a 60W light bulb form their power.

    Sunlight's efficency is about 90lm/watt so 90,000 lux is 90,000 lm/m^2 = 1000W/m^2
    You said your model was in KJ/m^2, presumably this is per second (Joules are a measure of energy not power) so KJ/m^2/s = kW/m^2
     
  6. Jul 28, 2008 #5
    Ok, that is perfectly clear...thank you again!
     
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