GNU Astronomy Utilities - Tasks: task #14775, Convolution with varying...
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task #14775: Convolution with varying PSF/Kernel over the image
Submitter: | Mohammad Akhlaghi <makhlaghi> | ||
Submitted: | Fri 15 Dec 2017 05:03:32 PM UTC | ||
Should Start On: | Thu 14 Dec 2017 11:00:00 PM UTC | Should be Finished on: | Thu 14 Dec 2017 11:00:00 PM UTC |
Category: | Convolve | Priority: | 5 - Normal |
Item Group: | Enhancement | Status: | Postponed |
Privacy: | Public | Assigned to: | None |
Percent Complete: | 0% | Open/Closed: | Open |
Effort: | 0.00 |
Sat 16 Dec 2017 03:50:15 PM UTC, comment #2: |
Mohammad Akhlaghi <makhlaghi> |
Sat 16 Dec 2017 01:54:23 AM UTC, comment #1: This is just a brainstorm which only works in the spatial domain.
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Mohammad Akhlaghi <makhlaghi> |
Fri 15 Dec 2017 05:03:32 PM UTC, original submission:
Currently the Convolve program can only take a single kernel to convolve the image with. This is the most basic/simple situation. To be more realistic, it would be good if Convolve can apply a varying a PSF across the dataset.
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Mohammad Akhlaghi <makhlaghi> |
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Date | Changed by | Updated Field | Previous Value | => | Replaced by |
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2017-12-15 | makhlaghi | Carbon-Copy | - | Added -email is unavailable- |
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After re-reading the suggestion, I thought of adding some further clarifications to the suggestion before:
1. By "If the kernels are all the same size ...", I meant the size of the kernel image (number of pixels it contains), not its FWHM. So for example, a kernel with a smaller FWHM would be padded with zeros to have the same image pixel "size" as that of a larger FWHM kernel. Ofcourse, it would be much more efficient if each image only has the number of pixels necessary to contain it. But that needs a little work (in checking the edges especially).
The kernel can also be larger than the image, although edge effects might not be negligible in such cases (see the edge effects in the spatial or frequency domain).
2. In the suggested scenario (which is based on Gnuastro's modular nature), the PSF interpolation (what region of the image needs what kernel) should be done by another program. Such an interpolation is beyond the scope of the Convolve program (for modularity).
A separate program (maybe called "Interpolate" and called on the command-line with `astinterpolate') can be added for such interpolations which can also do things like interpolating over blank pixels and generally any kind of interpolation/extrapolation.
As in any interpolation, we can go to the highest resolution (estimate a kernel for each pixel). But the basic idea of this scenario is this: how realistic is such (infinite) accuracy? Given all the error sources we have and also in the distant wings of the PSF which are the main concern, and our limited computing power, certain regions can reliably be considered as having/needing the same kernel.
But the important thing is that if this hypothetical interpolation program doesn't do what a user wants, the user can always define their own labels and kernels using their own tools (to the maximum resolution, if they want) and feed them into Convolve.