WorldView-1
WorldView-1 acquisitions are calibrated using the Orfeo Toolbox.
DN to Radiance
The WorldView-1 product handbook provides the formula below to convert the DN into radiance:
Where:
\(gain_{(b)}\) and \(offset_{(b)}\) are values taken from the table below:
Band | Gain | Offset |
pan | 1.016 | -1.824 |
And \(abscalfactor\) and \(effectivebandwith\) are extracted from the acquisition metadata.
The conversion from \(DN\) (for Digital Numbers) to spectral radiance (or ‘TOA radiance’) \(L \) is done with the formula below:
As such, the calibration uses:
and
\(L \) in \(W/m^2/steradians/micrometers\) with \(b\) being a band ID.
Radiance to Reflectance
To convert TOA radiance to TOA reflectance, the following formula is used :
where :
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\(L(b)\) is the spectral radiance for band b
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\(pi\) is the famous mathematical constant
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\(d\) is the earth-sun distance (in astronomical units) and depends on the acquisition’s day and month
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\(ESUN(b)\) is the mean TOA solar irradiance (or solar illumination) in \(W/m^2/micrometers\)
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\(θ\) is the solar zenith angle in degrees.
The values for the \(ESUN(b)\) are provided in the table below:
Common band name | Mean TOA solar irradiance |
pan | 1610.73 |
Input
The input is an ingested WorldView-1, see details here.
Output
The output is a STAC item geojson ... including the assets ...
References
RE01 - TODO add reference to slides about WorldView