[GRASS-dev] Does SUN_ELEVATION in Landsat's MTL file mean zenith for i.topo.corr?

GRASS GIS GRASS GIS developer
1

Sorry for cross-posting.

I would like a confirmation for the following, regarding i.topo.corr:

Is SUN_ELEVATION the requested zenith parameter (by i.topo.corr)?

So, given the entry "SUN_ELEVATION = 45.38304417" in the the metadata file
"LT51840322011266MOR00_MTL.txt", then, the production of an illumination model
requires "zenith=45.38304417".

Or is it "zenith = 90 - SUN_ELEVATION", thus it becomes
zenith = 90 - 45.38304417 = 44.616956

?

Thank you, Nikos

2

Hi Nikos,

generally zenith angle = 90 - SUN_ELEVATION ANGLE indeed.

Cheers,
Yann

On 8 January 2013 21:08, Nikos Alexandris <nik@nikosalexandris.net> wrote:

Sorry for cross-posting.

I would like a confirmation for the following, regarding i.topo.corr:

Is SUN_ELEVATION the requested zenith parameter (by i.topo.corr)?

So, given the entry "SUN_ELEVATION = 45.38304417" in the the metadata file
"LT51840322011266MOR00_MTL.txt", then, the production of an illumination model
requires "zenith=45.38304417".

Or is it "zenith = 90 - SUN_ELEVATION", thus it becomes
zenith = 90 - 45.38304417 = 44.616956

?

Thank you, Nikos
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Yann Chemin
Researcher@IWMI
Skype/FB: yann.chemin

3

Yann Chemin:

Hi Nikos,
generally zenith angle = 90 - SUN_ELEVATION ANGLE indeed.

Thank you for the confirmation Yann :slight_smile:

Best, Nikos

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