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  1. Data Management
  2. DM-8141

Clarify sizing for Object association

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      Architecture

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      Reading section 4.3.2 of DPDD and comparing it with DMS-REQ-0271, we have an inconsistency regarding the number of possible objects that are associated. DPDD states that the nearest 3 will be stored, whereas DMSR states that all the objects within TBD arcsec will be associated. Please clarify.

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            tjenness Tim Jenness added a comment -

            For now I am going to update DMS-REQ-0271 and DPDD to say nearest 3 but no farther than 5 arcsec (and define the 5 in a constraintBlock). Zeljko Ivezic please comment if you want something different.

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            tjenness Tim Jenness added a comment - For now I am going to update DMS-REQ-0271 and DPDD to say nearest 3 but no farther than 5 arcsec (and define the 5 in a constraintBlock). Zeljko Ivezic please comment if you want something different.
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            ctslater Colin Slater added a comment -

            "No farther than 5 arcsec" is too stringent; if a DIAObject is sitting inside a a galaxy that's 30 arcseconds wide, you want to associate with that even if the centroids are not within 5 arcseconds. I think the DPDD is purposefully vague for this reason.

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            ctslater Colin Slater added a comment - "No farther than 5 arcsec" is too stringent; if a DIAObject is sitting inside a a galaxy that's 30 arcseconds wide, you want to associate with that even if the centroids are not within 5 arcseconds. I think the DPDD is purposefully vague for this reason.
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            tjenness Tim Jenness added a comment -

            DPDD says "a few arcseconds" and implies that the maximum number of matches is 3. DMSR says "TBD arcsec". I will add the 3 to DMSR but leave the "TBD" intact. If you want to clarify the requirement in the DMSR further that's fine with me. My focus at the moment is trying to make DPDD and DMSR agree.

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            tjenness Tim Jenness added a comment - DPDD says "a few arcseconds" and implies that the maximum number of matches is 3. DMSR says "TBD arcsec". I will add the 3 to DMSR but leave the "TBD" intact. If you want to clarify the requirement in the DMSR further that's fine with me. My focus at the moment is trying to make DPDD and DMSR agree.
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            ktl Kian-Tat Lim added a comment -

            The baseline for this would seem to be on p. 32 of LDM-151 v/draft:

            DIASources will be positionally matched to the nearest 3 stars and 3 galaxies in the DRP Object database. In its simplest case the search algorithm will be a tree-based nearest neighbor search (the default radius for association is not defined). The matched Objects will be persisted as a measure of local environment.

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            ktl Kian-Tat Lim added a comment - The baseline for this would seem to be on p. 32 of LDM-151 v/draft: DIASources will be positionally matched to the nearest 3 stars and 3 galaxies in the DRP Object database. In its simplest case the search algorithm will be a tree-based nearest neighbor search (the default radius for association is not defined). The matched Objects will be persisted as a measure of local environment.
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            tjenness Tim Jenness added a comment -

            Wow. Okay, so I guess I have to change the requirements and DPDD to match that and update the table size to 6 rather than 3. LDM-151 isn't flowing down from DMSR or DPDD at the moment.

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            tjenness Tim Jenness added a comment - Wow. Okay, so I guess I have to change the requirements and DPDD to match that and update the table size to 6 rather than 3. LDM-151 isn't flowing down from DMSR or DPDD at the moment.
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            zivezic Zeljko Ivezic added a comment -

            If you need the maximum distance for the 3 nearest stars/galaxies,
            please use 1 arcmin.

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            zivezic Zeljko Ivezic added a comment - If you need the maximum distance for the 3 nearest stars/galaxies, please use 1 arcmin.
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            tjenness Tim Jenness added a comment -

            I have updated the radius to 1 arcminute for that requirement.

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            tjenness Tim Jenness added a comment - I have updated the radius to 1 arcminute for that requirement.
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            tjenness Tim Jenness added a comment -

            I have made the required changes to DMSR and DPDD.

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            tjenness Tim Jenness added a comment - I have made the required changes to DMSR and DPDD.

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              Assignee:
              tjenness Tim Jenness
              Reporter:
              tjenness Tim Jenness
              Watchers:
              Colin Slater, John Swinbank, Kian-Tat Lim, Tim Jenness, Zeljko Ivezic
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