@phil_browne Good morning Phil.

This method is used only for OSI-450-a, the v3 Climate Data Record (1978-2020).

We don't need it for the associated Interim CDR OSI-430-a (2021-onwards) because the ICDR uses #SSMIS only, and those missions have a small polar observation hole: it does not matter how we interpolate.

The new method was not used in our "v2" data (OSI-450 and OSI-430-b): we were using the isotropic interpolation even for the #SMMR period (which our users complained about).

We improved many things when we prepared the new (version 3) #SeaIce Concentration #ClimateData Record of the #OSISAF !

One aspects we improved is the treatment of the "polar observation hole" for the early #satellite missions #SMMR and #SSMI. We teamed-up with the University of Utah who had developed a new method for gap-filling.

Read about this collaboration here:
https://osi-saf.eumetsat.int/community/stories/advanced-gap-filling-techniques-sea-ice-concentration-climate-data-records

And grab the new #OSISAF #SIC data here:
https://osi-saf.eumetsat.int/products/osi-450-a