| 11 Oct 2011 12:22 PM |
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Hi, I need help to set my geometry parameters in FLAASH using Worldview2 and Quickbird data.
I have read on the FLAASH guide that “The azimuth angle is defined as the azimuth (the angle between the line of sight and due North) of the sensor as viewed from the ground. This angle is arbitrary for nadir-viewing sensors. Azimuth values must be between -180 and 180 degrees. For example, if your azimuth from the sensor is 90 degrees (due east), then the azimuth from the ground is -90 degrees (due west)”
In my metadata file I have this information: “meanSatAz”
meanSatAz = 291.6 (Worldview2) and meanSatAz = 36.3 (Quickbird)
Which values should I use in the Flaash module for both sensors and how can I calculate them?
Thank you for your help!
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MariM
Veteran Member
Posts:2396  
| 11 Oct 2011 02:07 PM |
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It seems that your WV2 dataset is defining azimuth using 360 degrees while FLAASH defines azimuth as +/-180. You only need to calculate where 291.6 would be if on a 180 degree semi-circle. So 360-291.6 = 68.4 degrees, but this would be on the negative side of the semi-circle, so it would be -68.4 (sensor is looking northwest). However, you need the perspective from the ground looking towards the sensor, which is its opposite. This would be 180-68.4 = 111.6 degrees (southeast).
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Deleted User
New Member
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| 11 Oct 2011 03:29 PM |
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Thank you very much for your help!
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Deleted User
New Member
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| 13 Oct 2011 02:20 PM |
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Another question about the Flaash Azimuth angle for Quickbird and Ikonos data.
For Quickbird in the metadata file I have the parameter (like for Worldview2) “meanSatAz: 36.3”, and for Ikonos the parameter “Nominal Collection Azimuth: 316.6835 degrees”. Are these the angles between the line of sight and the North (like Worldview2), or they are already the azimuth angles from the ground (so I should use directly them in Flaash)?
Thanks
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MariM
Veteran Member
Posts:2396
| 14 Oct 2011 08:10 AM |
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I would guess it is from the sensor and not the ground, which is less common. But you may want to contact the data provider to confirm this.
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Deleted User
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| 18 Oct 2011 10:57 AM |
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I asked the data provider, they told me:
-Ikonos: The "Nominal Collection Azimuth" value is defined as the "satellite azimuth from ground perspective."
-Quickbird: The "SatAZ" is the azimuth angle of the satellite with respect to the center of the image, in degrees from true north 0 to 360 degrees.
So for the FLAASH module, if I have understood correctly, for Ikons I can directly use the azimuth value they give me (only converting it in the range [-180, 180]), otherwise for Quickbird I need to make the same operation I do with Worldview2 data.
Is it right?
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Deleted User
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| 25 Mar 2013 09:18 PM |
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Hi Stephania!
Now that I read your posts I have had a light for processing my Ikonos image, but I still have a doubt. It is strictly necessary to subtract my Nominal Collectio Azimuth to 180. My Nominal Azimuth is 73.3913, so I am not sure if I need to convert that value to -180, 180 range.
Thank you,
Katherine
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