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I'm looking to make image cutouts of fixed pixel size for several hundred objects from the DES DR1 catalog. I notice that when specifying the size/FOV of the images (in degrees) when doing an SIA query, there can be slight variations (+- a few pixels) in image sizes for each cutout. Is there any way to fix the size of the image in pixels when querying?
asked Apr 8, 2019 by jasonpoh (150 points) | 59 views

1 Answer

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Hi Jason,

So it arises because the SIA query logic works in WCS coordinates, and does a conversion to pixel coordinates.  There is some rounding error in this conversion that will depend on position, so there isn't yet a way to enforce a fixed pixel size, other than specifying slightly larger than needed size and then trimming afterwards. We do have a rewrite underway to change the query logic to deal directly in pixel coordinates, and this will make the images return the same number of pixels, but this is not yet ready for deployment.

Knut Olsen
answered Apr 12, 2019 by anonymous

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