Andy Kellett
New Member
Posts:  
| 11 Apr 2017 12:17 PM |
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Hi, I am trying to rotate a large orthophoto with row crops to see the effect that will have on susceptibility to moire when I resize. I applied rotations of 17 and 23 degrees in the rotate/flip raster tool. In both instances I can see small changes in the image at small scales (fine patterns in the edges of the rows changed) but the overall row angle remained exactly the same. I expected the whole image to rotate by the amount I entered, and so I expected to see the row angle noticeably change. Do I misunderstand what that tool does?Thanks.
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Mari Minari
Veteran Member
Posts:1880 
| 11 Apr 2017 12:37 PM |
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The Rotate/Flip Data tool does exactly as it sounds - it will rotate the entire image by the amount you enter and it shows a small 'preview' of how that might look. So if you enter 17 (and select Enter so it is accepted in the dialog), it will rotate the image 17 degrees clockwise. Perhaps that isn't enough for your rows to be completely vertical or horizonal or even noticeable? What if you enter 90 degrees? The image should be rotated 90 degrees clockwise.
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Andy Kellett
New Member
Posts:
| 11 Apr 2017 12:49 PM |
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I took a closer look and see that when I look at the rotated raster layers they are displayed reprojected - so it makes sense. I guess I need to break out of my geospatial coordinate frame to see the rotation.
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Mari Minari
Veteran Member
Posts:1880
| 11 Apr 2017 12:51 PM |
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Yes, that is true when it is displayed on top of the original image. Try placing the result in a new View (go to Views->Two Vertical views or other). Then you should see the rotation.
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Andy Kellett
New Member
Posts:
| 11 Apr 2017 12:59 PM |
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yep - that did it - thanks
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