Geolocation issue with L2 Sentinel2 and Landsat8 products

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armin.mehrabian
Posts: 8
Joined: Tue Feb 25, 2020 10:44 am America/New_York

Geolocation issue with L2 Sentinel2 and Landsat8 products

by armin.mehrabian » Wed Feb 26, 2020 11:38 am America/New_York

Hi All,

I'm working on a process that requires,
    1. L2 processing Sentinel2 and Landsat8 scenes through l2gen
    2. Post-processing the Rrs outputs from step 1 outside seadas
    3. create geolocated geotiffs from step 2 results

In order to create geolocated geotiffs in step 3 I use python Rasterio package. For that Rasterio takes the 4 boundary values (eastmost_lon, northmost_lat, ...). Now, the issue is that some of the scenes processed in step 1 through l2gen in the output have invalid boundary coordinates under /Metadata/Global_Attributes like

northernmost_latitude  90.0  float32   
southernmost_latitude  -90.0  float32   
easternmost_longitude  180.0  float32   
westernmost_longitude  -180.0  float32   
geospatial_lat_units  degrees_north  ascii   
geospatial_lon_units  degrees_east  ascii   
geospatial_lat_max  90.0  float32   
geospatial_lat_min  -90.0  float32   
geospatial_lon_max  180.0  float32   
geospatial_lon_min  -180.0  float32   


However, Metadata/Scan_Line_Attributes seems to have array valid scan line coordinates under slat, elat, slon, elon, clat, clon. If you pick the 4 extreme coordinates from here they do not form a rectangular bounding box. As a side note when I load the l2gen processed output in QGIS, the Extend values, which seems to correspond to the 4 bounding coordinates does not agree with any of the Metadata/Scan_Line_Attributes coordinates.

I'd love to know if anyone has suggestion on how can I correctly create geolocated geotiffs from output of step 2.

Thanks,
Armin

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OB SeaDAS - dshea
Subject Matter Expert
Subject Matter Expert
Posts: 214
Joined: Thu Mar 05, 2009 10:25 am America/New_York

Geolocation issue with L2 Sentinel2 and Landsat8 products

by OB SeaDAS - dshea » Wed Feb 26, 2020 12:13 pm America/New_York

can you give me an L1 file where l2gen produces a coordinate box for the whole earth.  Remember, if the scene is near a pole this bounding box is correct.

don

armin.mehrabian
Posts: 8
Joined: Tue Feb 25, 2020 10:44 am America/New_York

Geolocation issue with L2 Sentinel2 and Landsat8 products

by armin.mehrabian » Wed Feb 26, 2020 4:41 pm America/New_York

Sure, here is the link to the L1 Sentinel2 scene. It is for an area over Peru.
https://drive.google.com/file/d/1fl_9tvkzKtiVQZf4vRr3g029CIsMH_2K/view?usp=sharing

and this is the L2 product file generated:
https://drive.google.com/file/d/1h_bpZdYkmoGxv0a1eGb_avjk0CotRvfl/view?usp=sharing

OB SeaDAS - dshea
Subject Matter Expert
Subject Matter Expert
Posts: 214
Joined: Thu Mar 05, 2009 10:25 am America/New_York

Geolocation issue with L2 Sentinel2 and Landsat8 products

by OB SeaDAS - dshea » Wed Mar 04, 2020 3:28 pm America/New_York

Yes, it looks like our L1 reader for MSI data is flagging any pixel with bad Lt as NAVFAIL.  The scene you sent has mostly bad Lt except in the lower corner, which caused problems for the code which sets the North, South, East, West metadata.  We have new software that can handle this situation and are working to get this into l2gen.

l1info uses the new stuff and can get you the correct limits:

$ l1info -i 100 manifest.safe

Sensor=MSIS2A
Orbit_Number=0
Number_of_Scans=5490
Number_of_Pixels_per_Scan=5490
Upper_Left_Lon=-68.211082
Upper_Left_Lat=-16.188877
Upper_Right_Lon=-68.153831
Upper_Right_Lat=-16.188658

INFO: FIRST SCAN LINE
Start_Date=2018-01-24T14:47:14.456Z

INFO: LAST SCAN LINE
End_Date=2018-01-24T14:47:31.646Z
Lower_Left_Lon=-68.254745
Lower_Left_Lat=-16.367836
Lower_Right_Lon=-67.972183
Lower_Right_Lat=-16.366648

SUMMARY STATS
Northernmost_Lat=-16.188662
Southernmost_Lat=-16.367836
Easternmost_Lon=-67.972183
Westernmost_Lon=-68.254761
Center_Lat=-67.974686
Center_Lon=0.000000
Start_Node=Ascending
End_Node=Descending
Daynight=Day
Moon_in_SV=0
gringpointlongitude=-68.21108,-68.15383,-67.97218,-68.25475
gringpointlatitude=-16.18888,-16.18866,-16.36665,-16.36784
gringpointsequence=1,2,3,4

don

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