2

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>
5
  • This sounds like an error in the header. Could you post the section in question? The sun elevation and sun angle should be scene center and associated with a single value. The swath size is not large enough to even require separate values for sun elevation as the would be quite uniform. I would imagine that if for some reason these values are valid your could just average them to acquire a single coefficient. Sep 17, 2014 at 16:24
  • ok.. I've edited the question and added the piece of header of "DIM_SPOT6_xxxxxx.XML" Sep 17, 2014 at 20:05
  • Another question is about the ESUN values to SPOT-6.. what are these values?? where are there? Sep 17, 2014 at 20:37
  • ESUN is the earth/sun distance and it is not a coefficient in the header. It is a standard distance based on Julian date. Here is a spreadsheet that has the values. google.com/… Sep 17, 2014 at 20:45
  • I referred to: solar exoatmospheric spectral irradiances of Spot 6. I seen that the reflectance equation is: rho=(PILdd)/(Eocos(SUN_ELEVATION)). Or maybe you know other equation for the SPOT-6?? Sep 17, 2014 at 20:48

1 Answer 1

1

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.

Your Answer

By clicking “Post Your Answer”, you agree to our terms of service, privacy policy and cookie policy

Not the answer you're looking for? Browse other questions tagged or ask your own question.