# Local data processing

**URL:** <https://discourse.oceanobservatories.org/t/local-data-processing/491>\
**Category:** HelpDesk\
**Tags:** cgsn\
**Created:** [May 17, 2022, 11:39am UTC](https://discourse.oceanobservatories.org/t/local-data-processing/491 "2022-05-17T11:39:10Z")\
**Posts on this page:** 6\
**Page:** 1

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**Author:** ![Chain](https://avatars.discourse-cdn.com/v4/letter/c/ce73a5/32.png) [@Chain](https://discourse.oceanobservatories.org/u/Chain)\
**Post date:** [May 17, 2022, 11:39am UTC](https://discourse.oceanobservatories.org/t/local-data-processing/491/1 "2022-05-17T11:39:10Z")

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Hello, I am trying to use the raw data directly downloaded from the website to calculate the corresponding variation, for example, potential density. However, I also notice there are some calibrations on the raw data before calculation (e.g., from Github). Is it necessary, or does it depend on the specific fields? Thanks.

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**Author:** ![swhite](https://yyz2.discourse-cdn.com/flex036/user_avatar/discourse.oceanobservatories.org/swhite/32/31_2.png) [@swhite](https://discourse.oceanobservatories.org/u/swhite)\
**Post date:** [May 17, 2022, 6:16pm UTC](https://discourse.oceanobservatories.org/t/local-data-processing/491/2 "2022-05-17T18:16:57Z")

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@Chain,

Can you provide us with a little more information? Which website are you downloading the data from? And which datasets are your looking at?

Thanks,  
Sheri  
OOI/CGSN Data Team

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**Author:** ![Chain](https://avatars.discourse-cdn.com/v4/letter/c/ce73a5/32.png) [@Chain](https://discourse.oceanobservatories.org/u/Chain)\
**Post date:** [May 18, 2022, 6:57am UTC](https://discourse.oceanobservatories.org/t/local-data-processing/491/3 "2022-05-18T06:57:51Z")

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Hi Sheri, thanks for your reply. The website I used to download the data is [Data Access & Visualization (oceanobservatories.org)](https://ooinet.oceanobservatories.org/data_access/?search=GA02HYPM#GA02HYPM-WFP02-05-VEL3DL000). Take this 3D velocity profiler for example. I notice that the vertical velocity has the order of about 0.1~0.01m/s, which is larger than the order (100m/day, or 0.001m/s) estimated from the omega equation in some studies. Does it mean that the vertical velocity field provided by the profiler should be calibrated first before using (or are they just invalid)? And if so, do any calibrations should be done on the horizontal velocity fields as well?  
Also, I am wondering about the difference between the telemetered and recovered CTD data. Does the latter have been calibrated? And is it necessary to apply the calibration coefficient on the original temperature/salinity/conductivity field before using it?

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**Author:** ![areed](https://avatars.discourse-cdn.com/v4/letter/a/e5b9ba/32.png) [@areed](https://discourse.oceanobservatories.org/u/areed)\
**Post date:** [May 19, 2022, 7:47pm UTC](https://discourse.oceanobservatories.org/t/local-data-processing/491/4 "2022-05-19T19:47:22Z")

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Hi @Chain ,  
Sorry about the confusion. While most VEL3D sensors report the data in mm/s and the system automatically converts to m/s, the sensor you pointed to (GA02HYPM-WFP02-05-VEL3DL000) is one of a few that were configured to report in cm/s. Consequently, the reported values in m/s are an order of magnitude too large. Sorry about that!

As for the differences between the telemetered and recovered CTD data - there should be none. The telemetered and recovered\_host data were stored on the mooring computer, whereas the recovered\_inst data was stored on-board the instrument. And there is no need to apply the calibration coefficient to the original temperature/conductivity fields. All the data is processed by the system with the appropriate calibration coefficients for that deployment and instrument to produce the temperature and practical salinity data.

Andrew,  
OOI/CGSN Data Team

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**Author:** ![Chain](https://avatars.discourse-cdn.com/v4/letter/c/ce73a5/32.png) [@Chain](https://discourse.oceanobservatories.org/u/Chain)\
**Post date:** [May 24, 2022, 7:15am UTC](https://discourse.oceanobservatories.org/t/local-data-processing/491/5 "2022-05-24T07:15:44Z")

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Thanks a lot for your replies.  
Regards,  
Chain

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**Author:** ![swhite](https://yyz2.discourse-cdn.com/flex036/user_avatar/discourse.oceanobservatories.org/swhite/32/31_2.png) [@swhite](https://discourse.oceanobservatories.org/u/swhite)\
**Post date:** [May 28, 2022, 6:09pm UTC](https://discourse.oceanobservatories.org/t/local-data-processing/491/6 "2022-05-28T18:09:22Z")

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