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New PO DAAC

PostPosted: Fri Sep 11, 2020 5:08 pm
by ermill99
I stumbled upon PO DAAC from the EarthData site as I am currently using subscriptions from MODIS-Aqua. I downloaded the .nc file and toyed with it in ARCGis but I cannot get it to look like the map on State of the Ocean. I am curious if I can set up subscriptions with Ocean Circulation like I have done with MODIS-Aqua where I can grab a PNG file for my set up regions?

Thank you

Re: New PO DAAC

PostPosted: Mon Sep 14, 2020 8:56 pm
by buckmaster
I'm not aware of a subscription service for the same MODIS-Aqua imagery that we use in SOTO.
However, for most of the layers in the State of the Oceans tool, PO.DAAC retrieves imagery from the NASA EOSDIS Global Imagery Browse Services (GIBS). You can find additional details about GIBS, and ways to access their imagery products through their page on the Earthdata Wiki, https://wiki.earthdata.nasa.gov/pages/viewpage.action?pageId=2228230

Since you mentioned ArcGIS, you might be interested in their detailed instructions for directly accessing GIBS imagery from various GIS clients, https://wiki.earthdata.nasa.gov/display/GIBS/Geographic+Information+System+%28GIS%29+Usage#expand-ESRIArcGISArcMap

Re: New PO DAAC

PostPosted: Tue Sep 15, 2020 4:44 am
by ermill99
Thank you for the reply. Yes, Modis has subscriptions available and use it to obtain SST and chloro-a images. I've been working with the .nc files and am more confused on how to populate the ocean current arrows. I think I have the map, figured out but need help getting the current arrows.

Re: New PO DAAC

PostPosted: Wed Sep 16, 2020 1:47 pm
by buckmaster
We include our data processing steps for the OSCAR ocean surface current vectors that can be visualized in SOTO (which renders tiled imagery). Perhaps, those can provide some ideas for your application?

1. Read u and v components from 5-day file.
2. Convert u and v into speed and direction.
3. Calculate the lon,lat locations of the 4 arrow vertices for every data pixel, such that speed and direction are depicted by the arrow.
4. Subdivide data into pyramid levels, and repeat arrow generation for the lower resolution levels of the pyramid.
5. Store arrows in the tiled groups of arrows and write group to KML file.
6. Store KML groups in quadtree.
7. Assign arrows to last day of the 5-day average, and create links for the same arrows to be used for the preceding 4 days.

Re: New PO DAAC

PostPosted: Wed Sep 16, 2020 2:04 pm
by dmoroni
Since you are an ArcGIS user already familiar with netCDF data files, I would suggest using the native file format for the OSCAR dataset, which also minimizes any errors in geolocation and/or data precision. That dataset can be accessed here: https://podaac.jpl.nasa.gov/dataset/OSC ... _third-deg
Direct data access is available on Drive: https://podaac-tools.jpl.nasa.gov/drive ... _third_deg
The following user guide provides additional guidance: https://podaac-tools.jpl.nasa.gov/drive ... dguide.pdf

Basically, you'll need to work with the native U and V vector components to Resolve the current velocity vector. The U and V components follow the oceanographic convention, so a positive U indicates surface water flowing to the East, and a positive V indicates surface water flowing to the North.

I am not an ArcGIS user, but the following ESRI article seems to provide the guidance you would need to rectify the vector arrows on to a map: https://www.esri.com/arcgis-blog/produc ... v-vectors/

I'll consult internally with our GIS experts and see if there's any more guidance we might be able to provide.