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[bug #64615] Fits program's --pixelareaonwcs only accurate on equator
From: |
Mohammad Akhlaghi |
Subject: |
[bug #64615] Fits program's --pixelareaonwcs only accurate on equator |
Date: |
Fri, 1 Sep 2023 15:08:03 -0400 (EDT) |
URL:
<https://savannah.gnu.org/bugs/?64615>
Summary: Fits program's --pixelareaonwcs only accurate on
equator
Group: GNU Astronomy Utilities
Submitter: makhlaghi
Submitted: Fri 01 Sep 2023 08:08:01 PM BST
Category: Warp
Severity: 3 - Normal
Item Group: Output not reasonable
Status: In Progress
Privacy: Public
Assigned to: makhlaghi
Open/Closed: Open
Discussion Lock: Any
_______________________________________________________
Follow-up Comments:
-------------------------------------------------------
Date: Fri 01 Sep 2023 08:08:01 PM BST By: Mohammad Akhlaghi <makhlaghi>
As of version 0.20.65, the recently added '--pixelareaonwcs' option of the
FITS program only reports correct values on the equator! As we go to higher or
lower declinations, the area of each pixel becomes artificially larger!
The problem can be reproduced with the commands below where we will produce
the same image, but once on a CRVAL2 (declination of reference point) of 0 and
once with a CRVAL2 of 50.
$ for d in 0 50; do \
echo "1 2 2 4 0 0 0 0 1 1" \
| astmkprof --oversample=1 --mergedsize=3,3 \
--mforflatpix --crval=180,$d \
-o ra180-dec$d.fits --quiet; \
astfits ra180-dec$d.fits --pixelareaonwcs --quiet; \
echo "Declination $d:"; \
aststatistics ra180-dec"$d"_pixarea.fits --minimum --maximum; \
done
The output is this (at declination of 50, the pixels are much larger!) While
in the TAN projection the reference point (center of this image) should have
the same pixel scale as CDELT (which is correct in the declination 0 scenario
here).
Declination 0:
6.944444e-11 6.944444e-11
Declination 50:
1.064109e-10 1.091394e-10
I am working on the fix now.
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- [bug #64615] Fits program's --pixelareaonwcs only accurate on equator,
Mohammad Akhlaghi <=