[gdal-dev] NetCDF driver getting wrong values if compared to HDF5

[Ivan Lucena]

Hi,

I am struggling with an issue with the NetCDF file with dealing with data from ESA Copernicus, Proba-V 1KM Level 3.

If I read the data using the HDF5 driver I lose the georeferenced but the values seems to more aceturate, since the pixels values over the ocean are supposed t be flagged as 254. See the Python printout:

from osgeo import gdal
import numpy​
​
ds = gdal.Open('HDF5:"c_gls_NDVI_201907110000_GLOBE_PROBAV_V2.2.1.nc"://NDVI')​
bd = ds.GetRasterBand(1)​
ar = bd.ReadAsArray(25109,9083,10,10)​
print(ar)​
ds = None​
​[[254 254 254 254 254 254 254 254 254 254]
 [254 254 254 254 254 254 254 254 254 254]​
 [254 254 254 254 254 254 254 254 254 254]​
 [254 254 254 254 254 254 254 254 254 254]​
 [254 254 254 254 254 254 254 254 254 254]​
 [254 254 254 254 254 254 254 254 254 254]​
 [254 254 254 254 254 254 254 254 254 254]​
 [254 254 254 254 254 254 254 254 254 254]​
 [254 254 254 254 254 254 254 254 254 254]​
 [254 254 254 254 254 254 254 254 254 254]]​

ds = gdal.Open('NETCDF:"c_gls_NDVI_201907110000_GLOBE_PROBAV_V2.2.1.nc":NDVI')​
bd = ds.GetRasterBand(1)​
ar = bd.ReadAsArray(25109,9083,10,10)​
print(ar)​
ds = None​
[[255 255 255 255 255 255 255 255 255 255]​
 [255 255 255 255 255 255 255 255 255 255]​
 [255 255 255 255 255 255 255 255 255 255]​
 [255 255 255 255 255 255 255 255 255 255]​
 [255 255 255 255 255 255 255 255 255 255]​
 [255 255 255 255 255 255 255 255 255 255]​
 [255 255 255 255 255 255 255 255 255 255]​
 [255 255 255 255 255 255 255 255 255 255]​
 [255 255 255 255 255 255 255 255 255 255]​
 [255 255 255 255 255 255 255 255 255 255]]​

By looking at the gdalinfo information it clear that netCDF gathers more information, like I said, georeferenced but both drivers are not capable to show the list of flagged values on the NDVI dataset:

$ gdalinfo HDF5:"c_gls_NDVI_201907110000_GLOBE_PROBAV_V2.2.1.nc"://NDVI
Driver: HDF5Image/HDF5 Dataset
. . .
    NDVI_flag_meanings=Missing cloud snow sea background
    NDVI_flag_values=√ⁿ²■

$ gdalinfo NETCDF:"c_gls_NDVI_201907110000_GLOBE_PROBAV_V2.2.1.nc":NDVI
Warning 1: NetCDF driver detected file type=5, but libnetcdf detected type=3
Warning 1: Unsupported netCDF datatype (7), treat as Float32.​
Driver: netCDF/Network Common Data Format
. . .
  NDVI#flag_meanings=Missing cloud snow sea background
  NDVI#flag_values={}

There is this warning but that doesn't seems to be affecting the pixels values on the land.

Does anybody has a clue on what is going on here?

Thanks,

Ivan

-------------- next part --------------
An HTML attachment was scrubbed...
URL: <http://lists.osgeo.org/pipermail/gdal-dev/attachments/20190730/90653faf/attachment.html>