Duplicate Terra granules between 2003 and 2017

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dem1
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Duplicate Terra granules between 2003 and 2017

by dem1 » Tue May 31, 2022 4:03 pm America/New_York

Hi,

It seems that the L2 browser returns duplicate products for MODIS Terra between around [2003-01-01, 2017-06-24] with roughly 320 granules per day instead of 190.
Example:
https://oceancolor.gsfc.nasa.gov/cgi/browse.pl?sub=level1or2&per=DAY&day=17332&prm=CHL&set=10&mon=17318&sen=tmod&rad=0&frc=0&n=39.7265625&w=5.2734375&id=1654026908.259537&cn=40.48&cs=38.95&cw=4.46&ce=6.04&dnm=D&file=T2017166104000.L2_LAC_OC.nc_CHLOR_A_BRS&ndx=0&wid=170&hgt=254
and
https://oceancolor.gsfc.nasa.gov/cgi/browse.pl?sub=level1or2&per=DAY&day=17332&prm=CHL&set=10&mon=17318&sen=tmod&rad=0&frc=0&n=39.7265625&w=5.2734375&id=1654026908.259537&cn=40.48&cs=38.95&cw=4.46&ce=6.04&dnm=D&file=T2017166104000.L2_LAC_OC.nc_CHLOR_A_BRS&ndx=1&wid=170&hgt=254

Is it normal? Seems like database duplicates.

We try to estimate the size of the whole archive and it seems these duplicates have a big impact on the estimate. We found 1943173 Terra granules vs 1193721 for Aqua which seems suspect if they have the same theoretical number of granules per day (Aqua mission has 22 years of data vs 20 years for Aqua).

Thanks,
Julien
Last edited by dem1 on Wed Jun 01, 2022 3:03 am America/New_York, edited 1 time in total.

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OB ODPS - towens
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Re: Duplicate Terra granules between 2003 and 2017

by OB ODPS - towens » Tue May 31, 2022 10:27 pm America/New_York

Our current holdings:
MODISA | level0 | 2,084,721
MODIST | level0 | 2,320,268

Tommy

dem1
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Re: Duplicate Terra granules between 2003 and 2017

by dem1 » Wed Jun 01, 2022 4:03 am America/New_York

Thanks for your answer Tommy, but this does not explain why the browser list duplicates L1? The two swaths in my example are real duplicates because L0 to L2 products have the same name.
I obtain my numbers by selecting the whole mission on the browser, select Day products only, then click on "Find swaths".

OB ODPS - towens
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Re: Duplicate Terra granules between 2003 and 2017

by OB ODPS - towens » Wed Jun 01, 2022 7:46 am America/New_York

The web developers are looking into the duplication in the browser results.

Tommy

OB ODPS - jgwilding
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Re: Duplicate Terra granules between 2003 and 2017

by OB ODPS - jgwilding » Wed Jun 01, 2022 11:16 am America/New_York

Hi Julien,

We are unable to reproduce the duplicate results. I've attached a screenshot from our browser where we have navigated to the same date. Can you post a screenshot that shows the duplicate results?

john
Screenshot from 2022-06-01 15-11-39.png
Screenshot from 2022-06-01 15-11-39.png (303.08 KiB) Not viewed yet
Screenshot from 2022-06-01 15-11-39.png
Screenshot from 2022-06-01 15-11-39.png (303.08 KiB) Not viewed yet

dem1
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Re: Duplicate Terra granules between 2003 and 2017

by dem1 » Wed Jun 01, 2022 11:40 am America/New_York

Hi John,

Below 4 screenshots for:
- the main L2 browser where I selected the sensor, date and then clicked on France on the map
- the search result which shows the 2 duplicates
- the detail of each duplicate where you can see at the bottom "Number of swaths: 1st of 2 swaths" for the first and "Number of swaths: 2nd of 2 swaths" for the second granule. All other info are identical.

Thanks,
Julien
Attachments
searchresult.png
searchresult.png (36.32 KiB) Not viewed yet
granule1.png
granule1.png (265.69 KiB) Not viewed yet
main.png
main.png (172.86 KiB) Not viewed yet

dem1
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Re: Duplicate Terra granules between 2003 and 2017

by dem1 » Wed Jun 01, 2022 11:41 am America/New_York

The second granule:
Attachments
granule2.png
granule2.png (265.44 KiB) Not viewed yet

OB ODPS - jgwilding
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Re: Duplicate Terra granules between 2003 and 2017

by OB ODPS - jgwilding » Wed Jun 01, 2022 12:39 pm America/New_York

Hi Julien.

Thank you for posting your screenshots. We have been able to replicate the problem and are investigating. It appears to be an issue with the query that is used for the page that results from the Find Swaths operation. The granules that appear as duplicates have the characteristic of having data for multiple days. It does not mean that we have duplicate copies of those granules in our archive.

john

dem1
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Re: Duplicate Terra granules between 2003 and 2017

by dem1 » Wed Jun 01, 2022 4:37 pm America/New_York

Thanks a lot John for the quick investigation!
Note that this granule doesn't seem to have data on multiple days because its start time is 10:40

OB WebDev - masoudso
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Re: Duplicate Terra granules between 2003 and 2017

by OB WebDev - masoudso » Wed Jun 08, 2022 2:05 pm America/New_York

Hi Julien,
This issue has been resolved.

Thanks,
Masoud

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