[GRASS-user] From Landsat radiance (W/m2*sr*µm) to Global horizontal irradiance (W/m2) for mere mortals...

[Andrés Oswaldo Calderón Romero]

Hello list,

We are working in a solar energy project to locate potential sites for solar panel farms. We are using the Landsat 7 panchromatic band to derive radiance with i.landsat.toar (W/m2*sr*µm units). Now, we have access to some ground data from sensors measuring global horizontal irradiance (GHI) which output is in W/m2 units.  I would like to compare these datasets for validation, so, my question is rather simple: ¿Is there a way to convert radiance in W/m2*sr*µm to irradiance in W/m2?

I have read in [1] that radiance = irradiance / π, but I don't completely understand, also, this doesn't take the spectral part (µm) into account.  I will very appreciate any further explanation about this... thank you very much in advance!!!

[1] http://earth.esa.int/landtraining07/D1LB3-Su.pdf

--
Atentamente,


ANDRES OSWALDO CALDERON ROMERO
M.Sc. Geoinformation Sciences & Earth Observation
Grupo de Investigación Aplicada en Sistemas - GRiAS
Universidad de Nariño
Pasto - Colombia
T: (+57) 301 382 9659

________________________________
Correo Electrónico - Universidad de Nariño
Pasto - Nariño - Colombia
www.udenar.edu.co
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