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Is there any way to rotate a raster w/o resampling? I am aware that rasters are always 90 deg perpendicular grids, but is there any file format or methodology that allows for a diagonal raster - one where the grid cells are actually angled akin to a vector?

I'm a new user, so I can't post images to show an example, but I want a raster to be rotated 18 degrees without the pixelation around the edges that is caused by nearest neighbor. We want original values, so bicubic and cubic convoultion won't do.

Thanks!

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  • The short answer is that the only rotations not requiring resampling are multiples of 90 degrees. If you want original values, you can accomplish that but you will either be discarding some of them (where two or more cells get rotated into a single cell) or allowing NoData gaps in some places. Given these unavoidable (mathematical) facts, perhaps we could help you find workarounds if you could say something about what you need to accomplish and what your constraints are.
    – whuber
    Commented May 2, 2012 at 19:56
  • I was given this assignment by my supervisor, and I'm not sure what he needs the data for (it might be proprietary), but essentially, he gave me an excel spreadsheet of xy coordinates with a Value attribute (it appears to be elevation). When the points are imported into ArcMap it creates a set of points 60*60, but angled at 18 degrees. We want to build a raster out of those points (centerpoints to 300ft cells) while retaining the exact values for the exact coordinates. Nearest neighbor shifts the coordinates and any other resampling changes the values.
    – kylebez
    Commented May 2, 2012 at 21:38
  • If it's ok to use a local coordinate system, do that, and adapt it to the directions of the coordinates so that the sides of the raster extent are parallel to the coordinate axes. Otherwise, you may be able to find an oblique projection with the same properties. The choice comes down to whether you may need to overlay other geographic data with this raster: if so, it must be in a known coordinate system. If you edit your question to clarify these needs, people can provide details of the workflow in their replies.
    – whuber
    Commented May 2, 2012 at 21:56
  • I'm not sure what is an appropriate workaround or not - that depends on the functionality they are looking for. I wasn't given much context. My task was essentially to find out if it could be done, and it seems like it cannot. But I've come up with a few workarounds of my own, such as adding noData points to create a 90 degree square and build a raster off of that, or using the vector rotation tool in the Hawth's Add-On, while keeping the old coordinates as an attribute. But if there is a way to do it without a workaround, and without coding a new raster format - thats what I'm looking for.
    – kylebez
    Commented May 3, 2012 at 0:52

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The short answer that @whuber provided as a Comment remains the only attempt to answer this Question:

The short answer is that the only rotations not requiring resampling are multiples of 90 degrees. If you want original values, you can accomplish that but you will either be discarding some of them (where two or more cells get rotated into a single cell) or allowing NoData gaps in some places. Given these unavoidable (mathematical) facts, perhaps we could help you find workarounds if you could say something about what you need to accomplish and what your constraints are.

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