bugGNU Astronomy Utilities - Bugs: bug #64615, Fits program's --pixelareaonwcs...

 
 

You are not allowed to post comments on this tracker with your current authentication level.

bug #64615: Fits program's --pixelareaonwcs only accurate on equator

Submitter:  Mohammad Akhlaghi <makhlaghi>
Submitted:  Fri 01 Sep 2023 07:08:01 PM UTC
   
 
Category:  Warp Severity:  3 - Normal
Item Group:  Output not reasonable Status:  Fixed
Privacy:  Public Assigned to:  makhlaghi
Open/Closed:  Closed

Sat 02 Sep 2023 11:25:18 PM UTC, comment #1: 

This bug has been fixed in Commit c3bd7956f1f4; see the description there for more.

While working on this a more fundamental problem was found in the area calculation function (see bug #64617).

Mohammad Akhlaghi <makhlaghi>
Group administrator
Fri 01 Sep 2023 07:08:01 PM UTC, original submission:  

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.

Mohammad Akhlaghi <makhlaghi>
Group administrator

 

(Note: upload size limit is set to 16384 kB, after insertion of the required escape characters.)

No files currently attached

 

Depends on the following items: None found

Items that depend on this one: None found

 

Carbon-Copy List
  • -email is unavailable- added by makhlaghi (Submitted the item)
  •  

    There are 0 votes so far. Votes easily highlight which items people would like to see resolved in priority, independently of the priority of the item set by tracker managers.

     

    Follow 2 latest changes.

    Date Changed by Updated Field Previous Value => Replaced by
    2023-09-02 makhlaghi StatusIn Progress Fixed
        Open/ClosedOpen Closed

    Back to the top

    Powered by Savane 3.13-4b48.
    Corresponding source code