taskGNU Astronomy Utilities - Tasks: task #15700, Make a HEALPix grid on the gaia...


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task #15700: Make a HEALPix grid on the gaia index catalogue

Submitted by:  Sachin Kumar Singh <sks_15>
Submitted on:  Sat 20 Jun 2020 07:00:42 AM UTC  
Should Start On:  Fri 19 Jun 2020 12:00:00 AM UTC Should be Finished on:  Fri 19 Jun 2020 12:00:00 AM UTC
Category:  New program Priority:  5 - Normal
Item Group:  New feature Status:  In Progress
Privacy:  Public Percent Complete:  100%
Assigned to:  Sachin Kumar Singh <sks_15> Open/Closed:  Closed
Effort:  0.00

Tue 30 Jun 2020 04:06:21 PM UTC, comment #4: 

All tasks are done and pushed here. There was an error due to `gal_polygon_vertices_sort` function in `polygon.c` which is fixed(see bug #58683). For temporary use, I've used `gal_polygon_vertices_sort_convex` for which the output is shown. Once the bug fix is merged, I'll replace it with the former function.

Sachin Kumar Singh <sks_15>
Project MemberIn charge of this item.
Sun 28 Jun 2020 12:00:14 AM UTC, comment #3: 

Great! Looks perfect! You are almost set for the next step (to find the various quadrilaterals, or quads for short, in the neighboring healpixs and generating the hashes)

But before that, to help in the debugging and visualization, write a simple C function that gets a list of polygons and generates a DS9 region file which will show the polygon over the image. In the next phases of your project, you will be using these quads a lot, so its good to be able to visualize everything easily ;-).

You already have one polygon (these 5 points), so go ahead and add that function. Then use it to upload a new image with the auto-generated DS9 region file loaded over the image and connecting the points ;-).

Close this task with that post, and we can go onto the next step ;-)...

Mohammad Akhlaghi <makhlaghi>
Project Administrator
Sat 27 Jun 2020 11:36:57 PM UTC, comment #2: 

Found the error. It was simply that the index we were using to make the region file was the one we took from the full Gaia catalogue. But when we were testing, we did it on PV fits file. So I simply changed the index for the current fits file and got the objects corresponding to that and made a region file and plotted in ds9. The result is shown below.

If everything is well, I can make a function from the current implementation, close this task and define the next task.

Sachin Kumar Singh <sks_15>
Project MemberIn charge of this item.
Thu 25 Jun 2020 08:51:52 PM UTC, comment #1: 

The work on this task is (hopefully) done:-)

I'm able to take out 5 brightest objects from the index and map it on the HEALPix. The code for the same is pushed here.

Changing `Nside` parameter only pixelates the grid further as shown in the 2 figures. Can you verify the correctness of the code, on the basis of these 2 figures(for 1st figure Nside=10, for 2nd Nside=100)?

(file #49371,

Sachin Kumar Singh <sks_15>
Project MemberIn charge of this item.
Sat 20 Jun 2020 07:00:42 AM UTC, original submission:  

The first step in task #15637 is to create a HEALPix grid on the Gaia catalogue on its brightest sources, each grid having the 5 bright sources. These sources will, later on, be used to make quad hash codes, which will be stored in a kd-tree.

This task is a subtask of task #15637.

Sachin Kumar Singh <sks_15>
Project MemberIn charge of this item.


Depends on the following items: None found

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    Follow 9 latest changes.

    Date Changed by Updated Field Previous Value => Replaced by
    2020-06-30 sks_15 Open/ClosedOpen => Closed
    2020-06-30 sks_15 Percent Complete0% => 100%
    2020-06-30 sks_15 Attached File- => Added Screenshot@from@2020-06-30@21-07-31.png, #49398
        Percent Complete90% => 0%
    2020-06-28 makhlaghi Percent Complete0% => 90%
    2020-06-27 sks_15 Attached File- => Added Screenshot@from@2020-06-28@05-01-10.png, #49380
    2020-06-27 sks_15 Attached File#49371 => Removed
    2020-06-25 sks_15 Attached File- => Added Screenshot@from@2020-06-26@01-53-47.png, #49371
        Attached File- => Added Screenshot@from@2020-06-26@01-56-06.png, #49372

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