taskGNU Astronomy Utilities - Tasks: task #16239, Customizable NoiseChisel...

 
 

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task #16239: Customizable NoiseChisel interpolation algorithms

Submitter:  Mohammad Akhlaghi <makhlaghi>
Submitted:  Sat 30 Jul 2022 03:18:35 PM UTC
   
 
Should Start On:  Fri 29 Jul 2022 11:00:00 PM UTC Should be Finished on:  Fri 29 Jul 2022 11:00:00 PM UTC
Category:  NoiseChisel Priority:  5 - Normal
Item Group:  Enhancement Status:  Postponed
Privacy:  Public Assigned to:  makhlaghi
Percent Complete:  0% Open/Closed:  Open
Effort:  0.00

Thu 02 Jan 2025 07:21:44 PM UTC, comment #1: 

This task has been generalized to allow different types of interpolation. A possible list includes:

  • Polynomial (the first comment below is a 0-th order polynomial).
  • Bilinear or bicubic interpolations. Petra Awad has demonstrated this to be good in some scenarios (where the polynomial cannot be used).


Fortunately both are available in the GNU Scientific Library (which Gnuastro uses for numerical methods). So it is just a matter of having time to implement them. Any help would be highly appreciated by someone who has basic C knowledge ;-).

Mohammad Akhlaghi <makhlaghi>
Group administrator
Sat 30 Jul 2022 03:18:35 PM UTC, original submission:  

Currently NoiseChisel does nearest neighbor interpolation for estimating the Sky and all the intermediary thresholds (like the quantile threshold and etc). This is done to remove gradients caused by the sky or prior processing steps.

But in some scenarios, the extended signal structure is very large (covering almost all the image) and low-S/N (and therefore not properly detectable). When it is possible to assume that the sky is a constant across the image, in such cases, we can simply use a single constant for our thresholds and Sky estimation.

Currently the only way we can do this is to use the `--checksky` option and use the statistics of the tiles used (before interpolation):


$ astnoisechisel image.fits --checksky --oneelempertile
$ sky=$(aststatistics image_sky.fits -hSKY --median)
$ astarithmetic image.fits $sky - --output=input-no-sky.fits


Mohammad Akhlaghi <makhlaghi>
Group administrator

 

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    Follow 3 latest changes.

    Date Changed by Updated Field Previous Value => Replaced by
    2025-01-02 makhlaghi Carbon-Copy- Added -email is unavailable-
    2025-01-02 makhlaghi SummaryNoiseChisel option to avoid interpolation for thresholds or Sky Customizable NoiseChisel interpolation algorithms
    2022-07-30 makhlaghi Carbon-Copy- Added -email is unavailable-

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