[gdal-dev] NetCDF and ESA Probav issue with corner coordimates

Fri Nov 1 01:45:20 PDT 2019

Hi Ivan,

I think I reported an issue like this some time ago in the QGIS issue
tracker:

https://issues.qgis.org/issues/20730

I think(!), but I hope some netcdf guru jumps in, that the crux is how
you define/interpret your data: is the value valid in the center of the
grid (like a raster) or is it on the vertices (more like a mesh).
It is all about interpretation of a datamodel: is it a grid or a raster.

If I understand correctly in a mesh (and netcdf) is much more possible
then in a raster: triangular meshes, non-regular etc etc:

https://docs.qgis.org/3.4/en/docs/user_manual/working_with_mesh/mesh_properties.html

I'm not sure who should be responsible for 'correcting/transforming'
this: a netcdf which is written as if the values are on (for example)
the upper-left corner vertices, while you actually mean the value is in
the center of a (grid)cell... For a simple rectangular mesh, this seems
feasible on the client side (see panoply example in first link), but for
non-regular meshes/netcdf's this seems impossible client side (well
actually that is not a raster/grid anymore)..

In your case I would think that the data is actually mend to be a grid...

Not sure if this is helpfull, as said I hope some netcdf guru jumps in.
Maybe I'm oversimplifying here...

Regards,

Richard Duivenvoorde

On 31/10/2019 22.06, Ivan Lucena wrote:
> 
> Hi Folks,
> 
> I Downloaded NetCDF files
> from http://land.copernicus.eu/global/products/ndvi and I am having
> problems with the GeoTransform that the driver is getting.
> 
> The image extents, as you can see in following gdalinfo report, goes
> beyond the -180 and +180 longitude degrees (half resolution, half pixel)
> but that's OK according to page 27 in the PDF documentation:
> PROBAV-Products_User_Manual_v1.3.pdf
> <https://earth.esa.int/documents/700255/1929094/PROBAV-Products_User_Manual_v1.3.pdf/fd5e30f4-5305-4d41-86aa-fab7b9568251> 
> 
> But if I open that image on QGIS and overlay a vector (GADM from
> gadm.org) or any other global layer it is clear that -180x80 should be
> in the upper left corner of the image, not In the center. There is a
> half pixel missing on the left and bottom of the image. This in in Fiji:
> 
> 
> 
> The gdalinfo report shows that the crs:GeoTransform is -180.0000000000
> 0.0029761905 0.0 80.0000000000 0.0 -0.0029761905 but it seems like the
> driver decided to take that to as center of the pixel based. Looking at
> the NetCDF source I can see that there this possibility exists.
> 
> Of course, I am not waiting for a solution. I just used gdal_translate
> "- a_ullr" and fix that into the target format. It takes centuries to
> converted that image to geotiff. But I am concerned that others might
> get in trouble because of that.
> 
> I tried to contact the data provider but did not received an answer yet.
> 
> Does anybody has experience with that dataset and/or NetCDF that can
> help figure out what is going on. It is a bug in the driver or an issue
> with the data.
> 
> Thanks,
> 
> -
> Ivan
> 
> Here is the gdalinfo report:
> 
> Don't worry about the warnings in regards to the pixel values. It is fine.
> 
> $ gdalinfo netcdf:c_gls_NDVI300_201910110000_GLOBE_PROBAV_V1.0.1.nc
> --debug on
> GDAL_netCDF: driver detected file type=5, libnetcdf detected type=3
> Warning 1: NetCDF driver detected file type=5, but libnetcdf detected
> type=3
> GDAL_netCDF: setting file type to 3, was 5
> GDAL_netCDF: dim_count = 2
> GDAL_netCDF: var_count = 4
> GDAL_netCDF: NCDFGetAttr unsupported type 7 for attribute _FillValue
> GDAL_netCDF: NCDFGetAttr unsupported type 7 for attribute missing_value
> GDAL_netCDF: NCDFGetAttr unsupported type 7 for attribute flag_values
> GDAL_netCDF: NCDFGetAttr unsupported type 7 for attribute valid_range
> GDAL_netCDF:
> =====
> SetProjectionFromVar( 3)
> *GDAL_netCDF: got grid_mapping crs*
> GDAL_netCDF: bIsGdalFile=1 bIsGdalCfFile=0 bBottomUp=0
> GDAL_netCDF: got spheroid from CF: (6378137.000000 , 298.257224)
> GDAL_netCDF: set bBottomUp = 0 from Y axis
> GDAL_netCDF: setting WKT from CF
> GDAL_netCDF: SetProjection, WKT =
> GEOGCS["unknown",DATUM["unknown",SPHEROID["Spheroid",6378137,298.257223563]],PRIMEM["Greenwich",0],UNIT["degree",0.0174532925199433,AUTHORITY["EPSG","9122"]]]
> 
> GDAL_netCDF: xdim: 120960 nSpacingBegin: 3 nSpacingMiddle: 3
> nSpacingLast: 3
> GDAL_netCDF: ydim: 47040 nSpacingBegin: -3 nSpacingMiddle: -3
> nSpacingLast: -3
> GDAL_netCDF: setting WKT from GDAL
> GDAL_netCDF: SetProjection, WKT = GEOGCS["WGS
> 84",DATUM["WGS_1984",SPHEROID["WGS
> 84",6378137,298.257223563,AUTHORITY["EPSG","7030"]],TOWGS84[0,0,0,0,0,0,0],AUTHORITY["EPSG","6326"]],PRIMEM["Greenwich",0,AUTHORITY["EPSG","8901"]],UNIT["degree",0.0174532925199433,AUTHORITY["EPSG","9108"]],AUTHORITY["EPSG","4326"]]
> 
> *GDAL_netCDF:
> SetGeoTransform(-180.001488,0.002976,0.000000,80.001488,0.000000,-0.002976)
> *
> GDAL_netCDF: bGotGeogCS=1 bGotCfSRS=1 bGotCfGT=1 bGotGdalSRS=1 bGotGdalGT=0
> Warning 1: Unsupported netCDF datatype (7), treat as Float32.
> GDAL_netCDF: NCDFGetAttr unsupported type 7 for attribute _FillValue
> GDAL_netCDF: netcdf type=5 gdal type=6 signedByte=1
> GDAL_netCDF: NCDFGetAttr unsupported type 7 for attribute _FillValue
> GDAL_netCDF: NCDFGetAttr unsupported type 7 for attribute missing_value
> GDAL_netCDF: NCDFGetAttr unsupported type 7 for attribute flag_values
> GDAL_netCDF: NCDFGetAttr unsupported type 7 for attribute valid_range
> GDAL_netCDF: got add_offset=-0.07999999821186066, status=0
> GDAL_netCDF: got scale_factor=0.004000000189989805, status=0
> GDAL: GDALOpen(netcdf:c_gls_NDVI300_201910110000_GLOBE_PROBAV_V1.0.1.nc,
> this=00000219E2D291F0) succeeds as netCDF.
> Driver: netCDF/Network Common Data Format
> GDAL: GDALDefaultOverviews::OverviewScan()
> Files: none associated
> Size is 120960, 47040
> Coordinate System is:
> GEOGCS["WGS 84",
>     DATUM["WGS_1984",
>         SPHEROID["WGS 84",6378137,298.257223563,
>             AUTHORITY["EPSG","7030"]],
>         TOWGS84[0,0,0,0,0,0,0],
>         AUTHORITY["EPSG","6326"]],
>     PRIMEM["Greenwich",0,
>         AUTHORITY["EPSG","8901"]],
>     UNIT["degree",0.0174532925199433,
>         AUTHORITY["EPSG","9108"]],
>     AUTHORITY["EPSG","4326"]]
> *Origin = (-180.001488095238102,80.001488095238088)*
> Pixel Size = (0.002976190476204,-0.002976190476190)
> Metadata:
> *  crs#GeoTransform=-180.0000000000 0.0029761905 0.0 80.0000000000 0.0
> -0.0029761905*
>   crs#grid_mapping_name=latitude_longitude
>   crs#inverse_flattening=298.257223563
>   crs#longitude_of_prime_meridian=0
>   crs#long_name=coordinate reference system
>   crs#semi_major_axis=6378137
>   crs#spatial_ref=GEOGCS["WGS 84",DATUM["WGS_1984",SPHEROID["WGS
> 84",6378137,298.257223563,AUTHORITY["EPSG","7030"]],TOWGS84[0,0,0,0,0,0,0],AUTHORITY["EPSG","6326"]],PRIMEM["Greenwich",0,AUTHORITY["EPSG","8901"]],UNIT["degree",0.0174532925199433,AUTHORITY["EPSG","9108"]],AUTHORITY["EPSG","4326"]]
> 
>   crs#_CoordinateAxisTypes=GeoX GeoY
>   crs#_CoordinateTransformType=Projection
>   lat#axis=Y
>   lat#DIMENSION_LABELS=lat
>   lat#long_name=latitude
>   lat#standard_name=latitude
>   lat#units=degrees_north
>   lat#_CoordinateAxisType=Lat
>   lon#axis=X
>   lon#DIMENSION_LABELS=lon
>   lon#long_name=longitude
>   lon#standard_name=longitude
>   lon#units=degrees_east
>   lon#_CoordinateAxisType=Lon
>   NC_GLOBAL#archive_facility=VITO
>   NC_GLOBAL#Conventions=CF-1.6
>   NC_GLOBAL#copyright=Copernicus Service information 2019
>   NC_GLOBAL#history=Processing line NDVI: 2019-10-22
>  
> NC_GLOBAL#identifier=urn:cgls:global:ndvi300_v1_333m:NDVI300_201910110000_GLOBE_PROBAV_V1.0.1
> 
>   NC_GLOBAL#institution=VITO NV
>   NC_GLOBAL#long_name=Normalized Difference Vegetation Index
>   NC_GLOBAL#orbit_type=LEO
>   NC_GLOBAL#parent_identifier=urn:cgls:global:ndvi300_v1_333m
>   NC_GLOBAL#platform=Proba-V
>   NC_GLOBAL#processing_level=L3
>   NC_GLOBAL#processing_mode=Near Real Time
>   NC_GLOBAL#product_version=V1.0.1
>   NC_GLOBAL#references=http://land.copernicus.eu/global/products/ndvi
>   NC_GLOBAL#sensor=VEGETATION
>   NC_GLOBAL#source=Derived from EO satellite imagery
>   NC_GLOBAL#time_coverage_end=2019-10-20T23:59:59Z
>   NC_GLOBAL#time_coverage_start=2019-10-11T00:00:00Z
>   NC_GLOBAL#title=10-daily Normalized Difference Vegetation Index 333M:
> GLOBE 2019-10-11T00:00:00Z
>   NDVI#add_offset=-0.079999998
>   NDVI#flag_meanings=Missing cloud snow sea background
>   NDVI#flag_values={}
>   NDVI#grid_mapping=crs
>   NDVI#long_name=Normalized Difference Vegetation Index 333M
>   NDVI#missing_value=
>   NDVI#scale_factor=0.0040000002
>   NDVI#standard_name=normalized_difference_vegetation_index
>   NDVI#units=
>   NDVI#valid_range={}
>   NDVI#_FillValue=
> OGRCT: PROJ >= 4.8.0 features enabled
> OGRCT: Using locale-safe proj version
> OGRCT: Source: +proj=longlat +ellps=WGS84 +towgs84=0,0,0,0,0,0,0 +no_defs
> OGRCT: Target: +proj=longlat +ellps=WGS84 +towgs84=0,0,0,0,0,0,0 +no_defs
> Corner Coordinates:
> *Upper Left  (-180.0014881,  80.0014881) (180d 0' 5.36"W, 80d 0' 5.36"N)*
> *Lower Left  (-180.0014881, -59.9985119) (180d 0' 5.36"W, 59d59'54.64"S)*
> *Upper Right ( 179.9985119,  80.0014881) (179d59'54.64"E, 80d 0' 5.36"N)*
> *Lower Right ( 179.9985119, -59.9985119) (179d59'54.64"E, 59d59'54.64"S)*
> Center      (  -0.0014881,  10.0014881) (  0d 0' 5.36"W, 10d 0' 5.36"N)
> Band 1 Block=120960x1 Type=Float32, ColorInterp=Undefined
>   NoData Value=0
>   Offset: -0.0799999982118607,   Scale:0.00400000018998981
>   Metadata:
>     add_offset=-0.079999998
>     flag_meanings=Missing cloud snow sea background
>     flag_values={}
>     grid_mapping=crs
>     long_name=Normalized Difference Vegetation Index 333M
>     missing_value=
>     NETCDF_VARNAME=NDVI
>     scale_factor=0.0040000002
>     standard_name=normalized_difference_vegetation_index
>     units=
>     valid_range={}
>     _FillValue=
> GDAL:
> GDALClose(netcdf:c_gls_NDVI300_201910110000_GLOBE_PROBAV_V1.0.1.nc,
> this=00000219E2D291F0)
> 
> 
> 
> _______________________________________________
> gdal-dev mailing list
> gdal-dev at lists.osgeo.org
> https://lists.osgeo.org/mailman/listinfo/gdal-dev
> 