I have a Spot-6 image and the metadata contain 9 values of SUN_ELEVATION (BottomRight BottomCenter BottomLeft CenterRight Center CenterLeft TopRight TopCenter TopLeft). I've used before Landsat and this contained 1 value of SUN_ELEVATION for use in the flectance equation. Now I don't know how will use these values in the equation to calculate sin(SUN_ELEVATION). How I should combine these values?
ANOTHER QUESTION IS ABOUT THE ESUN VALUES TO SPOT-6.. WHAT ARE THESE VALUES??.. WHERE ARE THERE??
The header for the first question is:
<Located_Geometric_Values>
<LOCATION_TYPE>TopRight</LOCATION_TYPE>
<COL>23169</COL>
<ROW>1</ROW>
<TIME>2014-04-17T15:13:27.828000Z</TIME>
<SATELLITE_ALTITUDE>701584.630405</SATELLITE_ALTITUDE>
<Acquisition_Angles>
<AZIMUTH_ANGLE>20.5991408203</AZIMUTH_ANGLE>
<VIEWING_ANGLE_ACROSS_TRACK>-1.90302747221</VIEWING_ANGLE_ACROSS_TRACK>
<VIEWING_ANGLE_ALONG_TRACK>12.12965768</VIEWING_ANGLE_ALONG_TRACK>
<VIEWING_ANGLE>12.3394936579</VIEWING_ANGLE>
<INCIDENCE_ANGLE_ALONG_TRACK>-12.8322522348</INCIDENCE_ANGLE_ALONG_TRACK>
<INCIDENCE_ANGLE_ACROSS_TRACK>5.13233998335</INCIDENCE_ANGLE_ACROSS_TRACK>
<INCIDENCE_ANGLE>13.7633382493</INCIDENCE_ANGLE>
</Acquisition_Angles>
<Solar_Incidences>
<SUN_AZIMUTH>62.3148341003</SUN_AZIMUTH>
<SUN_ELEVATION>54.9137375042</SUN_ELEVATION>
</Solar_Incidences>
<Ground_Sample_Distance>
<GSD_ACROSS_TRACK>2.14080821911</GSD_ACROSS_TRACK>
<GSD_ALONG_TRACK>2.3337350258</GSD_ALONG_TRACK>
</Ground_Sample_Distance>
</Located_Geometric_Values>
<Located_Geometric_Values>
<LOCATION_TYPE>CenterLeft</LOCATION_TYPE>
<COL>1</COL>
<ROW>5418</ROW>
<TIME>2014-04-17T15:13:28.832000Z</TIME>
<SATELLITE_ALTITUDE>701597.12665</SATELLITE_ALTITUDE>
<Acquisition_Angles>
<AZIMUTH_ANGLE>30.6025825529</AZIMUTH_ANGLE>
<VIEWING_ANGLE_ACROSS_TRACK>-4.51029940362</VIEWING_ANGLE_ACROSS_TRACK>
<VIEWING_ANGLE_ALONG_TRACK>12.7678042112</VIEWING_ANGLE_ALONG_TRACK>
<VIEWING_ANGLE>13.6401205795</VIEWING_ANGLE>
<INCIDENCE_ANGLE_ALONG_TRACK>-12.9524184599</INCIDENCE_ANGLE_ALONG_TRACK>
<INCIDENCE_ANGLE_ACROSS_TRACK>8.10746086821</INCIDENCE_ANGLE_ACROSS_TRACK>
<INCIDENCE_ANGLE>15.2135360829</INCIDENCE_ANGLE>
</Acquisition_Angles>
<Solar_Incidences>
<SUN_AZIMUTH>62.4597352167</SUN_AZIMUTH>
<SUN_ELEVATION>54.6058551573</SUN_ELEVATION>
</Solar_Incidences>
<Ground_Sample_Distance>
<GSD_ACROSS_TRACK>2.16790984064</GSD_ACROSS_TRACK>
<GSD_ALONG_TRACK>2.33122811517</GSD_ALONG_TRACK>
</Ground_Sample_Distance>
</Located_Geometric_Values>
<Located_Geometric_Values>
<LOCATION_TYPE>Center</LOCATION_TYPE>
<COL>11586</COL>
<ROW>5418</ROW>
<TIME>2014-04-17T15:13:28.889000Z</TIME>
<SATELLITE_ALTITUDE>701597.834082</SATELLITE_ALTITUDE>
<Acquisition_Angles>
<AZIMUTH_ANGLE>25.2806645718</AZIMUTH_ANGLE>
<VIEWING_ANGLE_ACROSS_TRACK>-3.13630286198</VIEWING_ANGLE_ACROSS_TRACK>
<VIEWING_ANGLE_ALONG_TRACK>12.4550951922</VIEWING_ANGLE_ALONG_TRACK>
<VIEWING_ANGLE>12.9859855447</VIEWING_ANGLE>
<INCIDENCE_ANGLE_ALONG_TRACK>-12.9212204779</INCIDENCE_ANGLE_ALONG_TRACK>
<INCIDENCE_ANGLE_ACROSS_TRACK>6.38122383831</INCIDENCE_ANGLE_ACROSS_TRACK>
<INCIDENCE_ANGLE>14.4843704031</INCIDENCE_ANGLE>
</Acquisition_Angles>
<Solar_Incidences>
<SUN_AZIMUTH>62.3396191484</SUN_AZIMUTH>
<SUN_ELEVATION>54.7446239807</SUN_ELEVATION>
</Solar_Incidences>
<Ground_Sample_Distance>
<GSD_ACROSS_TRACK>2.14574425486</GSD_ACROSS_TRACK>
<GSD_ALONG_TRACK>2.34669128077</GSD_ALONG_TRACK>
</Ground_Sample_Distance>
</Located_Geometric_Values>
<Located_Geometric_Values>
<LOCATION_TYPE>CenterRight</LOCATION_TYPE>
<COL>23169</COL>
<ROW>5418</ROW>
<TIME>2014-04-17T15:13:28.945000Z</TIME>
<SATELLITE_ALTITUDE>701598.530095</SATELLITE_ALTITUDE>
<Acquisition_Angles>
<AZIMUTH_ANGLE>19.9565074408</AZIMUTH_ANGLE>
<VIEWING_ANGLE_ACROSS_TRACK>-1.76271955049</VIEWING_ANGLE_ACROSS_TRACK>
<VIEWING_ANGLE_ALONG_TRACK>12.1425169852</VIEWING_ANGLE_ALONG_TRACK>
<VIEWING_ANGLE>12.3332746441</VIEWING_ANGLE>
<INCIDENCE_ANGLE_ALONG_TRACK>-12.8909872182</INCIDENCE_ANGLE_ALONG_TRACK>
<INCIDENCE_ANGLE_ACROSS_TRACK>4.6455241327</INCIDENCE_ANGLE_ACROSS_TRACK>
<INCIDENCE_ANGLE>13.7567884142</INCIDENCE_ANGLE>
</Acquisition_Angles>
<Solar_Incidences>
<SUN_AZIMUTH>62.2195675283</SUN_AZIMUTH>
<SUN_ELEVATION>54.8833713072</SUN_ELEVATION>
</Solar_Incidences>
<Ground_Sample_Distance>
<GSD_ACROSS_TRACK>2.12313579954</GSD_ACROSS_TRACK>
<GSD_ALONG_TRACK>2.36323624406</GSD_ALONG_TRACK>
</Ground_Sample_Distance>
</Located_Geometric_Values>
<Located_Geometric_Values>
<LOCATION_TYPE>BottomLeft</LOCATION_TYPE>
<COL>1</COL>
<ROW>10833</ROW>
<TIME>2014-04-17T15:13:29.951000Z</TIME>
<SATELLITE_ALTITUDE>701611.055334</SATELLITE_ALTITUDE>
<Acquisition_Angles>
<AZIMUTH_ANGLE>30.0393683451</AZIMUTH_ANGLE>
<VIEWING_ANGLE_ACROSS_TRACK>-4.37063958883</VIEWING_ANGLE_ACROSS_TRACK>
<VIEWING_ANGLE_ALONG_TRACK>12.7794685841</VIEWING_ANGLE_ALONG_TRACK>
<VIEWING_ANGLE>13.609226307</VIEWING_ANGLE>
<INCIDENCE_ANGLE_ALONG_TRACK>-12.9915180426</INCIDENCE_ANGLE_ALONG_TRACK>
<INCIDENCE_ANGLE_ACROSS_TRACK>7.82212237621</INCIDENCE_ANGLE_ACROSS_TRACK>
<INCIDENCE_ANGLE>15.1795500477</INCIDENCE_ANGLE>
</Acquisition_Angles>
<Solar_Incidences>
<SUN_AZIMUTH>62.3651154507</SUN_AZIMUTH>
<SUN_ELEVATION>54.5756410132</SUN_ELEVATION>
</Solar_Incidences>
<Ground_Sample_Distance>
<GSD_ACROSS_TRACK>2.1593044921</GSD_ACROSS_TRACK>
<GSD_ALONG_TRACK>2.33896262245</GSD_ALONG_TRACK>
</Ground_Sample_Distance>
</Located_Geometric_Values>
<Located_Geometric_Values>
<LOCATION_TYPE>BottomCenter</LOCATION_TYPE>
<COL>11586</COL>
<ROW>10833</ROW>
<TIME>2014-04-17T15:13:30.006000Z</TIME>
<SATELLITE_ALTITUDE>701611.745696</SATELLITE_ALTITUDE>
<Acquisition_Angles>
<AZIMUTH_ANGLE>24.6777067024</AZIMUTH_ANGLE>
<VIEWING_ANGLE_ACROSS_TRACK>-2.99633305079</VIEWING_ANGLE_ACROSS_TRACK>
<VIEWING_ANGLE_ALONG_TRACK>12.4673539097</VIEWING_ANGLE_ALONG_TRACK>
<VIEWING_ANGLE>12.9674591697</VIEWING_ANGLE>
<INCIDENCE_ANGLE_ALONG_TRACK>-12.9701540154</INCIDENCE_ANGLE_ALONG_TRACK>
<INCIDENCE_ANGLE_ACROSS_TRACK>5.99494281947</INCIDENCE_ANGLE_ACROSS_TRACK>
<INCIDENCE_ANGLE>14.4641360419</INCIDENCE_ANGLE>
</Acquisition_Angles>
<Solar_Incidences>
<SUN_AZIMUTH>62.2446915519</SUN_AZIMUTH>
<SUN_ELEVATION>54.7143402244</SUN_ELEVATION>
</Solar_Incidences>
<Ground_Sample_Distance>
<GSD_ACROSS_TRACK>2.13259585466</GSD_ACROSS_TRACK>
<GSD_ALONG_TRACK>2.36533405587</GSD_ALONG_TRACK>
</Ground_Sample_Distance>
</Located_Geometric_Values>
<Located_Geometric_Values>
<LOCATION_TYPE>BottomRight</LOCATION_TYPE>
<COL>23169</COL>
<ROW>10833</ROW>
<TIME>2014-04-17T15:13:30.061000Z</TIME>
<SATELLITE_ALTITUDE>701612.424576</SATELLITE_ALTITUDE>
<Acquisition_Angles>
<AZIMUTH_ANGLE>19.3139141146</AZIMUTH_ANGLE>
<VIEWING_ANGLE_ACROSS_TRACK>-1.62244118348</VIEWING_ANGLE_ACROSS_TRACK>
<VIEWING_ANGLE_ALONG_TRACK>12.1553682721</VIEWING_ANGLE_ALONG_TRACK>
<VIEWING_ANGLE>12.3270833097</VIEWING_ANGLE>
<INCIDENCE_ANGLE_ALONG_TRACK>-12.9497282578</INCIDENCE_ANGLE_ALONG_TRACK>
<INCIDENCE_ANGLE_ACROSS_TRACK>4.15857053102</INCIDENCE_ANGLE_ACROSS_TRACK>
<INCIDENCE_ANGLE>13.7502691903</INCIDENCE_ANGLE>
</Acquisition_Angles>
<Solar_Incidences>
<SUN_AZIMUTH>62.1243336098</SUN_AZIMUTH>
<SUN_ELEVATION>54.8530184038</SUN_ELEVATION>
</Solar_Incidences>
<Ground_Sample_Distance>
<GSD_ACROSS_TRACK>2.10545648282</GSD_ACROSS_TRACK>
<GSD_ALONG_TRACK>2.39275823656</GSD_ALONG_TRACK>
</Ground_Sample_Distance>
</Located_Geometric_Values>
</Use_Area> </Geometric_Data>
Best Answer
It looks like you are trying to directly apply the radiometric calibration equations from the Landsat handbook to SPOT. The equations are slightly different because the DN calibration method is different. Take a look at the SPOT 5/6 handbook for the correct equations. You also want to use the solar zenith (not elevation) as the theta parameter.
Here is a paper that extends the reflectance radiometric calibration to include atmospheric correction.