[gnuastro-devel] [task #14750] MakeCatalog take separate tiles as input

[Mohammad Akhlaghi]

URL:
  <http://savannah.gnu.org/task/?14750>

                 Summary: MakeCatalog take separate tiles as input
                 Project: GNU Astronomy Utilities
            Submitted by: makhlaghi
            Submitted on: Sun 26 Nov 2017 09:58:31 PM CET
         Should Start On: Sun 26 Nov 2017 12:00:00 AM CET
   Should be Finished on: Sun 26 Nov 2017 12:00:00 AM CET
                Category: MakeCatalog
                Priority: 5 - Normal
              Item Group: Enhancement
                  Status: Postponed
                 Privacy: Public
        Percent Complete: 0%
             Assigned to: None
             Open/Closed: Open
         Discussion Lock: Any
                  Effort: 0.00

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Details:

Currently MakeCatalg needs a single labeled image as input for each catalog it
makes (objects or clumps). This however, doesn't allow over-lapping regions.

To parse over each labeled region, MakeCatalog defines a tile and parses over
that tile in parallel. Therefore it is possible that the labeled regions are
given as tiles (not a whole image). This will also allow weights to be given
to pixels and thus deblending of objects: to possibly use only a fraction of a
pixel's value for objects that overlap. 

This was partially discussed in arXiv:1611.06387
<https://arxiv.org/abs/1611.06387> (also see the slides for graphical
demonstrations).

The inputs can be separate tiles (small labeled regions), and their WCS can be
used to match them onto the input image. Since each labeled region would be
separate in this system, the labeled tiles can be a binary image (when there
is no deblending). Binary images can be efficiently stored in bit format and
for different levels (number of layers) of deblending, we can use wider
integer types.

To be most efficient we can use the "Variable-length arrays" of the FITS
binary table standard to efficiently keep tiles of different sizes in bit-wise
or higher-width types. A simple program can be written to convert a
multi-extension FITS file (containing the labeled tiles) to such a FITS binary
table for easy transmission and storage. This can be very useful in future
surveys, see arXiv:1611.06387 <https://arxiv.org/abs/1611.06387>.




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