Reprojecting S3B-OLCI Level-2 Reduced Resolution to GeoTIFF

[jvaldezch]

I'm downloading some IOP from different sensor (Aqua, Terra, Virrs and Sentinel L2) data from your website and so far I managed to properly reproject Aqua, Terra and Virrs raster information and in those cases I have use GDAL (GDAL Warp) to do it. But when I try to do it wth Sentinel-3 Level-2 Reduced Resolution A and B it fails. It seems that metadata is different that data contained.

I'm missing a file or which is the projection coordinates used for this files?

Any help will be appreciated.

Code: Select all

file_in = "S3B_OLCI_ERRNT.20250101T164657.L2.IOP.NRT.nc"

band = xr.open_rasterio(
    f"NETCDF:{file_in}:/geophysical_data/bbp_443"
)

printr(band.rio.crs)

band.rio.write_crs("EPSG:4326 ", inplace=True)
band_reprojected = band.rio.reproject("EPSG:4326")
band_reprojected.rio.to_raster(file_tmp)

Take a look at coordinates in QGIS 3.4 (image below).

qgis_3_4.png (110.06 KiB) Not viewed yet

[OB SeaDAS - dshea]

Nothing about this file jumps out as a problem. Seadas had no problem displaying this L2 file.

S3B_OLCI_ERRNT_20250101T164657_L2_IOP_NRT_a_443.png (26.42 KiB) Not viewed yet

Maybe GDAL has a problem with full orbit files that cross the dateline.

[jvaldezch]

Got it! So subsetting the image first might help. Thanks!

[mdsumner]

The coordinate arrays are recognized as "geolocation arrays":

```
gdalinfo NETCDF:"S3B_OLCI_ERRNT.20250101T164657.L2.IOP.NRT.nc":/geophysical_data/bb_443

...
Geolocation:
SRS=GEOGCS["WGS 84",DATUM["WGS_1984",SPHEROID["WGS 84",6378137,298.257223563,AUTHORITY["EPSG","7030"]],AUTHORITY["EPSG","6326"]],PRIMEM["Greenwich",0,AUTHORITY["EPSG","8901"]],UNIT["degree",0.0174532925199433,AUTHORITY["EPSG","9122"]],AXIS["Latitude",NORTH],AXIS["Longitude",EAST],AUTHORITY["EPSG","4326"]]
X_DATASET=NETCDF:"S3B_OLCI_ERRNT.20250101T164657.L2.IOP.NRT.nc":/navigation_data/longitude
X_BAND=1
Y_DATASET=NETCDF:"S3B_OLCI_ERRNT.20250101T164657.L2.IOP.NRT.nc":/navigation_data/latitude
Y_BAND=1
PIXEL_OFFSET=0
PIXEL_STEP=1
LINE_OFFSET=0
LINE_STEP=1
GEOREFERENCING_CONVENTION=PIXEL_CENTER
...

```

so I tried these which seem fine. Use '-te', '-tr', and '-ts' in combination with '-t_srs' for the desired output grid.


```
gdalwarp NETCDF:"S3B_OLCI_ERRNT.20250101T164657.L2.IOP.NRT.nc":/geophysical_data/bb_443 ll.tif
gdalwarp NETCDF:"S3B_OLCI_ERRNT.20250101T164657.L2.IOP.NRT.nc":/geophysical_data/bb_443 laea.tif -t_srs "+proj=laea +lon_0=-150 +lat_0=-65"
```