<div dir="ltr">Thank you Nikos & Marcus,<div><br></div><div>Converting to TOA radiance (or reflectance) is not really the issue... I have already been following "Absolute Radiometric Calibration, Prepared By: Michele A. Kuester" using the formula for L (done in R, screenshot attached). I do think it is necessary that this be done in FLOAT32 to retain enough detail and per DigitalGlobe recommendations.</div><div><br></div><div>So, if I covert to TOA radiance as you've described, I am left with 32-bit pixels. I then import the images using r.in.gdal and launch i.atcorr. <b>Would the input range then be 0, 4294967295 (i.e. (2^32) - 1)? </b></div><div><b><br></b></div><div>If so, I wonder what a good output range might be, as I presume using r.out.gdal on a 32-bit image could take a long time.</div><div><br></div><div>Thank you for your help,</div><div>Paige</div></div><br><div class="gmail_quote"><div dir="ltr" class="gmail_attr">On Wed, Apr 8, 2020 at 6:31 AM <<a href="mailto:nik@nikosalexandris.net">nik@nikosalexandris.net</a>> wrote:<br></div><blockquote class="gmail_quote" style="margin:0px 0px 0px 0.8ex;border-left:1px solid rgb(204,204,204);padding-left:1ex">On 2020-04-08 15:17, Markus Neteler wrote:<br>
..<br>
> I believe that you need to apply the formula along with the respective<br>
> band calibration values ABSCALFACTOR and  EFFECTIVEBANDWIDTH (the same<br>
> is also stored in the IMD files) from the XML metadata files:<br>
> <br>
> grep 'ABSCALFACTOR\|EFFECTIVEBANDWIDTH'<br>
> 058891334020_01_P001_MUL/18DEC03184338-M2AS-058891334020_01_P001.XML<br>
>             <ABSCALFACTOR>9.295654000000000e-03</ABSCALFACTOR><br>
>             <br>
> <EFFECTIVEBANDWIDTH>4.730000000000000e-02</EFFECTIVEBANDWIDTH><br>
>             <ABSCALFACTOR>9.748051000000001e-03</ABSCALFACTOR><br>
>             <br>
> <EFFECTIVEBANDWIDTH>5.430000000000000e-02</EFFECTIVEBANDWIDTH><br>
>             <ABSCALFACTOR>7.541495000000000e-03</ABSCALFACTOR><br>
>             <br>
> <EFFECTIVEBANDWIDTH>6.300000000000000e-02</EFFECTIVEBANDWIDTH><br>
>             <ABSCALFACTOR>5.101088000000000e-03</ABSCALFACTOR><br>
>             <br>
> <EFFECTIVEBANDWIDTH>3.740000000000000e-02</EFFECTIVEBANDWIDTH><br>
>             <ABSCALFACTOR>1.103623000000000e-02</ABSCALFACTOR><br>
>             <br>
> <EFFECTIVEBANDWIDTH>5.740000000000000e-02</EFFECTIVEBANDWIDTH><br>
>             <ABSCALFACTOR>4.539619000000000e-03</ABSCALFACTOR><br>
>             <br>
> <EFFECTIVEBANDWIDTH>3.930000000000000e-02</EFFECTIVEBANDWIDTH><br>
>             <ABSCALFACTOR>1.224380000000000e-02</ABSCALFACTOR><br>
>             <br>
> <EFFECTIVEBANDWIDTH>9.890000000000000e-02</EFFECTIVEBANDWIDTH><br>
>             <ABSCALFACTOR>9.042234000000000e-03</ABSCALFACTOR><br>
>             <br>
> <EFFECTIVEBANDWIDTH>9.959999999999999e-02</EFFECTIVEBANDWIDTH><br>
> <br>
> Citing from "Absolute Radiometric Calibration, Prepared By: Michele A. <br>
> Kuester"<br>
> <a href="https://dg-cms-uploads-production.s3.amazonaws.com/uploads/document/file/209/ABSRADCAL_FLEET_2016v0_Rel20170606.pdf" rel="noreferrer" target="_blank">https://dg-cms-uploads-production.s3.amazonaws.com/uploads/document/file/209/ABSRADCAL_FLEET_2016v0_Rel20170606.pdf</a><br>
> <br>
>   "The top-of-atmosphere radiance, L, in units of Wμm-1m-2sr-1, is<br>
> then found from the DigitalGlobe<br>
>     image product for each band by converting from digital numbers<br>
> (DN) using the equation,<br>
> <br>
>     L = Gain * DN * (abscalfactor/effective bandwidth) + Offset<br>
> <br>
>     The TDI specific "abscalfactor" and "effectiveBandwidth" are<br>
> delivered with the imagery in the metadata file.<br>
>     The digital number, DN, is the pixel value found in the imagery.<br>
> The Gain and Offset are the absolute<br>
>     radiometric calibration band dependent adjustment factors that are<br>
> given in Table 1. Note that these<br>
>     are not necessarily stagnant values and they are revisited <br>
> annually.<br>
>  "<br>
> <br>
> (the "Table 1" is found in the same PDF file above. You may want to<br>
> check if a newer table version exists).<br>
> <br>
> You can apply this formula with r.mapcalc, for each band to obtain TOA<br>
> data from DN.<br>
<br>
See also <a href="https://gitlab.com/NikosAlexandris/i.worldview.toar" rel="noreferrer" target="_blank">https://gitlab.com/NikosAlexandris/i.worldview.toar</a> or <br>
<a href="https://github.com/NikosAlexandris/i.worldview.toar" rel="noreferrer" target="_blank">https://github.com/NikosAlexandris/i.worldview.toar</a>.<br>
<br>
Maybe useful (though ratehr badly programmed at the time).<br>
<br>
Nikos<br>
</blockquote></div><br clear="all"><div><br></div>-- <br><div dir="ltr" class="gmail_signature"><div dir="ltr"><b><font face="monospace, monospace">Paige Byassee</font></b><div><font face="monospace, monospace">Appalachian State University '19</font></div><div><font face="monospace, monospace">B.S., Ecology|Certificate in GIS</font></div><div><font face="monospace, monospace">(704)488-0872</font></div><div><font face="monospace, monospace"><a href="mailto:byasseepaige@gmail.com" target="_blank">byasseepaige@gmail.com</a></font></div></div></div>