Rather than complain, do it?

[joa-quim]

It it detects the cube, it can as well set -Q

grdinfo U.nc
grdinfo [WARNING]: Detected a data cube (U.nc) but -Q not set - skipping

[PaulWessel]

True, that.

[seisman]

https://github.com/pydata/xarray-data/raw/master/eraint_uvz.nc

This netcdf file was used in a PyGMT test added by @weiji14. I don't know much about this dataset, but it's likely not a grid cube.

In GMT 6.3.0, GMT reports an error, so it looks reasonable to me:

$ gmt grdinfo -C eraint_uvz.nc -Q
grdinfo [WARNING]: No 3-D array in file eraint_uvz.nc.  Selecting first 3-D slice in the 4-D array z
grdinfo [ERROR]: No 3rd-dimension coordinate vector found in eraint_uvz.nc
grdinfo [ERROR]: gmtapi_import_cube: Unable to examine cube eraint_uvz.nc.
[Session gmt (0)]: Error returned from GMT API: GMT_RUNTIME_ERROR (79)
[Session gmt (0)]: Error returned from GMT API: GMT_RUNTIME_ERROR (79)

In GMT dev (maybe after #6592), it crashes:

$ gmt grdinfo -C eraint_uvz.nc -Vd
....
grdinfo [DEBUG]: Found readable file eraint_uvz.nc
grdinfo [DEBUG]: Object ID 0 : Registered Grid File eraint_uvz.nc as an Input resource with geometry Surface [n_objects = 1]
grdinfo [DEBUG]: gmtapi_begin_io: Input resource access is now enabled [container]
grdinfo [DEBUG]: gmtapi_import_grid: Passed ID = 0 and mode = 1
grdinfo [DEBUG]: Found readable file eraint_uvz.nc
grdinfo [DEBUG]: Calling nc_open on eraint_uvz.nc, ncid = 65536, err = 0
grdinfo [INFORMATION]: No 2-D array in file eraint_uvz.nc.  Selecting first 2-D slice in the 4-D array z
grdinfo [DEBUG]: Calling nc_close on ncid 65536, err = 0
grdinfo [DEBUG]: Calling nc_open on eraint_uvz.nc, ncid = 65536, err = 0
grdinfo [INFORMATION]: No 2-D array in file eraint_uvz.nc.  Selecting first 2-D slice in the 4-D array z
grdinfo [INFORMATION]: No range attribute, guessing registration to be gridline
ERROR: Caught signal number 11 (Segmentation fault: 11) at
0   libgmt.6.4.0.dylib                  0x0000000103d72afc gmtnc_grd_info + 8556
1   ???                                 0x0000600802f15138 0x0 + 105587525374264
Stack backtrace:
0   libgmt.6.4.0.dylib                  0x0000000103df8789 sig_handler_unix + 217
1   libsystem_platform.dylib            0x00007ff81de48e2d _sigtramp + 29
2   libsystem_c.dylib                   0x00007ff85f65e7a0 __global_locale + 0
3   libgmt.6.4.0.dylib                  0x0000000103d43eda gmtlib_read_grd_info + 106
4   libgmt.6.4.0.dylib                  0x0000000103d113e0 gmtapi_import_grid + 5392
5   libgmt.6.4.0.dylib                  0x0000000103d08da8 gmtapi_import_data + 392
6   libgmt.6.4.0.dylib                  0x0000000103cf4dec gmtapi_get_data + 348
7   libgmt.6.4.0.dylib                  0x0000000103cec2ee GMT_Read_Data + 4910
8   libgmt.6.4.0.dylib                  0x0000000103fa225f GMT_grdinfo + 4047
9   libgmt.6.4.0.dylib                  0x0000000103cfd284 GMT_Call_Module + 2180
10  gmt                                 0x00000001036993c8 main + 1816
11  dyld                                0x0000000109f194fe start + 462

[joa-quim]

Apparently not an easy case. When I try to open it with Mirone

But GDAL clearly say it's a cube (well, a multi cube file).

gdalinfo eraint_uvz.nc
Driver: netCDF/Network Common Data Format
Files: eraint_uvz.nc
Size is 512, 512
Metadata:
  NC_GLOBAL#Conventions=CF-1.0
  NC_GLOBAL#Info=Monthly ERA-Interim data. Downloaded and edited by [email protected]
Subdatasets:
  SUBDATASET_1_NAME=NETCDF:"eraint_uvz.nc":z
  SUBDATASET_1_DESC=[2x3x241x480] geopotential (16-bit integer)
  SUBDATASET_2_NAME=NETCDF:"eraint_uvz.nc":u
  SUBDATASET_2_DESC=[2x3x241x480] eastward_wind (16-bit integer)
  SUBDATASET_3_NAME=NETCDF:"eraint_uvz.nc":v
  SUBDATASET_3_DESC=[2x3x241x480] northward_wind (16-bit integer)

Though it resists being open with

julia> UVW = gdaltranslate("NETCDF:eraint_uvz.nc:u");
ERROR: BoundsError: attempt to access 480×241×6 Array{Float32, 3} at index [480×241 Matrix{Bool}]
Stacktrace:

and also my HDFexplorer viewer say it's an "not recognizable format"

[PaulWessel]

I'll try to have a look on the weekend, but must also prepare a seminar for Wednesday in Southampton.

[seisman]

After PR #6615, the output is:

$ gmt grdinfo eraint_uvz.nc -Cn
-180	179.25	-90	90	66825.5	66825.5	0.75	0.75	480	241	0	1

After PR #6620, the output is:

$ gmt grdinfo eraint_uvz.nc -Cn
grdinfo [WARNING]: No 3-D array in file eraint_uvz.nc.  Selecting first 3-D slice in the 4-D array z
-180	179.25	-90	90	200	850	66825.5	66825.5	0.75	0.75	0	480	241	3	0	1

Can you please verify that the new output is correct?

[PaulWessel]

Sure. ncdump -h is all we need:

 ncdump -h eraint_uvz.nc 
netcdf eraint_uvz {
dimensions:
	longitude = 480 ;
	latitude = 241 ;
	level = 3 ;
	month = 2 ;
variables:
	float longitude(longitude) ;
		longitude:_FillValue = NaN ;
		longitude:units = "degrees_east" ;
		longitude:long_name = "longitude" ;
	float latitude(latitude) ;
		latitude:_FillValue = NaN ;
		latitude:units = "degrees_north" ;
		latitude:long_name = "latitude" ;
	int level(level) ;
		level:units = "millibars" ;
		level:long_name = "pressure_level" ;
	short z(month, level, latitude, longitude) ;
		z:number_of_significant_digits = 5 ;
		z:units = "m**2 s**-2" ;
		z:scale_factor = -1.7250274674968 ;
		z:long_name = "Geopotential" ;
		z:add_offset = 66825.5 ;
		z:_FillValue = NaN ;
		z:standard_name = "geopotential" ;
	short u(month, level, latitude, longitude) ;
		u:number_of_significant_digits = 2 ;
		u:units = "m s**-1" ;
		u:scale_factor = -0.00157270493804553 ;
		u:long_name = "U component of wind" ;
		u:add_offset = 26.96875 ;
		u:_FillValue = NaN ;
		u:standard_name = "eastward_wind" ;
	short v(month, level, latitude, longitude) ;
		v:number_of_significant_digits = 2 ;
		v:units = "m s**-1" ;
		v:scale_factor = -0.000477819996337667 ;
		v:long_name = "V component of wind" ;
		v:add_offset = -1.46875 ;
		v:_FillValue = NaN ;
		v:standard_name = "northward_wind" ;
	int month(month) ;

// global attributes:
		:Conventions = "CF-1.0" ;
		:Info = "Monthly ERA-Interim data. Downloaded and edited by [email protected]" ;
}

You can see z, u, and v are all 4-D matrices.