Skip to content

KOMPSAT-3/3A

KOMPSAT-3 and KOMPSAT-3A acquisitions are calibrated using the Orfeo Toolbox.

DN to Radiance

For the conversion from DN to spectral radiance (or ‘TOA radiance’) \(L \), the following formula is used :

\[ L(b) = {DN(b) \times gain(b)} + bias(b) \]

\(L \) in \(W/m^2/steradians/micrometers\) with \(b\) being a band ID.

The gain and bias values are read from the acquisition metadata.

Radiance to TOA Reflectance

To convert TOA radiance to TOA reflectance, the following formula is used :

\[ R(b) = { {\pi \times L(b) \times d \times d} \over {ESUN(b) \times cos(θ)} } \]

where :

  • \(L(b)\) is the spectral radiance for band b

  • \(pi\) is the famous mathematical constant

  • \(d\) is the earth-sun distance (in astronomical units) and depends on the acquisition’s day and month

  • \(ESUN(b)\) is the mean TOA solar irradiance (or solar illumination) in \(W/m^2/micrometers\)

  • \(θ\) is the solar zenith angle in degrees.

The values for the ESUN are provided in the tables below:

KOMPSAT-3

Band Nominal

bandpass

(nm)

50% bandpass (nm) Center (nm) Bandwidth

(nm)

ESUN
Blue 450 - 520 445.6 – 532.3 489.0 86.7 1970.281
Green 520 - 600 511.9 – 606.1 559.0 94.2 1814.155
Red 630 - 690 633.1 – 702.8 668.0 69.7 1516.303
NIR 760 - 900 756.0 – 932.2 844.1 176.2 1024.850

KOMPSAT-3A

Band Nominal

bandpass (nm)

50% bandpass (nm) Center (nm) Bandwidth

(nm)

ESUN
Blue 450 - 520 445.6 – 532.3 489.0 86.7 2001
Green 520 - 600 511.9 – 606.1 559.0 94.2 1875
Red 630 - 690 633.1 – 702.8 668.0 69.7 1525
NIR 760 - 900 756.0 – 932.2 844.1 176.2 1027

Input

The input is an ingested KOMPSAT-3 or KOMPSAT-3A, see details here.

Output

The output is a STAC item geojson ... including the assets ...

References

RW01 - OTB Optical calibration