taskGNU Astronomy Utilities - Tasks: task #14639, Program to identify points...


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task #14639: Program to identify points inside/outside a region

Submitted by:  Mohammad Akhlaghi <makhlaghi>
Submitted on:  Sun 24 Sep 2017 11:26:37 PM UTC  
Should Start On:  Sun 24 Sep 2017 10:00:00 PM UTC Should be Finished on:  Sun 24 Sep 2017 10:00:00 PM UTC
Category:  New program Priority:  5 - Normal
Item Group:  Enhancement Status:  Postponed
Privacy:  Public Percent Complete:  0%
Assigned to:  None Open/Closed:  Open
Effort:  0.00

Thu 28 Sep 2017 11:12:22 PM UTC, comment #1: 

The region covered by most surveys can be represented with a convex polygon (see gal_polygon_ordered_corners).

However, some larger surveys (like the GOODS or CANDELS) can have saw-like borders which are represented by a concave polygon.

Therefore to be generic, this task is not independent of task #13658 (Work on concave polygons too). Once `gal_polygon_ordered_corners' also works on concave polygons (task #13658 is complete), the suggested program by this task will also work on any generic survey field.

Mohammad Akhlaghi <makhlaghi>
Project Administrator
Sun 24 Sep 2017 11:26:37 PM UTC, original submission:  

Astronomical surveys are limited to a certain area of the sky (which can usually be represented nicely as the coordinates of a polygon).

While working on a catalog of objects, some of the objects might fall within the region of the survey we want to study and some might fall outside of it.

It would thus be very useful to have a program in Gnuastro that takes a region and a catalog of objects and identifies which of the objects are inside (or outside) that region.

Just as an initial brainstorm the program interface might look like the following:

$ astregion --region=region.txt catalog.txt

The `region.txt' file could be a standard SAO DS9 region output which is very commonly used. It will work generally on any coordinate system (as long as the region and catalog have the same coordinates, like both are RA-Dec). But we must ensure that it works on RA-Dec coordinates (where the region/polygon cover pass the equator or celestial pole).

Ofcourse, the input region doesn't have to be a polygon, any user interface for any shape can be defined. Following ds9's region file convention should be a good start.

This task was defined during a discussion with Leindert Boogaard.

Mohammad Akhlaghi <makhlaghi>
Project Administrator


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