taskGNU Astronomy Utilities - Tasks: task #14750, MakeCatalog take separate tiles as...


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task #14750: MakeCatalog take separate tiles as input

Submitted by:  Mohammad Akhlaghi <makhlaghi>
Submitted on:  Sun 26 Nov 2017 08:58:31 PM UTC  
Should Start On:  Sat 25 Nov 2017 11:00:00 PM UTC Should be Finished on:  Sat 25 Nov 2017 11:00:00 PM UTC
Category:  MakeCatalog Priority:  5 - Normal
Item Group:  Enhancement Status:  Postponed
Privacy:  Public Percent Complete:  0%
Assigned to:  None Open/Closed:  Open
Effort:  0.00

Sun 26 Nov 2017 08:58:31 PM UTC, original submission:  

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 (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.

Mohammad Akhlaghi <makhlaghi>
Project Administrator


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