Issue reading a NC-file in 0.5.2

[mauro3]

This does not work anymore on 0.5.2

julia> using Downloads, Rasters; Downloads.download("https://people.ee.ethz.ch/~werderm/903870/nc.nc", "nc.nc")                                                                                                           
"nc.nc"                                                                                                                                                                                         
                                                                                                                                                                                                
julia> RasterStack("nc.nc")                                                                                                                                                                     
ERROR: MethodError: no method matching Raster(::Char, ::Tuple{}, ::Tuple{}, ::Symbol, ::DimensionalData.Dimensions.LookupArrays.Metadata{Rasters.NCDsource, Dict{String, Any}}, ::Missing)      
...

on 0.5.1 it works fine (Julia 1.9.0). Note the file is about 800MB.

Here the stacktrace:

julia> RasterStack("nc.nc")                                                                                                                                                            [129/485]
ERROR: MethodError: no method matching Raster(::Char, ::Tuple{}, ::Tuple{}, ::Symbol, ::DimensionalData.Dimensions.LookupArrays.Metadata{Rasters.NCDfile, Dict{String, Any}}, ::Missing)        
                                                                                                                                                                                                
Closest candidates are:                                                                                                                                                                         
  Raster(::A, ::D, ::R, ::Na, ::Me, ::Mi) where {T, N, D<:Tuple, R<:Tuple, A<:AbstractArray{T, N}, Na, Me, Mi}                                                                                  
   @ Rasters ~/.julia/packages/Rasters/U9GgU/src/array.jl:251                                                                                                                                   
  Raster(::Any, ::Tuple; name, kw...)                                                                                                                                                           
   @ Rasters ~/.julia/packages/Rasters/U9GgU/src/array.jl:270                                                                                                                                   
  Raster(::Any, ::AbstractString, ::Any; crs, mappedcrs, dims, refdims, name, metadata, missingval, source, write, lazy)                                                                        
   @ Rasters ~/.julia/packages/Rasters/U9GgU/src/array.jl:295                                                                                                                                   
  ...                                                                                                                                                                                           
                                                                                                                                                                                                
Stacktrace:                                                                                                                                                                                     
  [1] rebuild(A::Raster{Char, 0, Tuple{}, Tuple{}, CommonDataModel.CFVariable{Char, 0, NCDatasets.Variable{Char, 0, NCDatasets.NCDataset{Nothing}}, NCDatasets.Attributes{NCDatasets.NCDataset{N
othing}}, NamedTuple{(:fillvalue, :missing_values, :scale_factor, :add_offset, :calendar, :time_origin, :time_factor), Tuple{Nothing, Tuple{}, Vararg{Nothing, 5}}}}, Symbol, DimensionalData.Di
mensions.LookupArrays.Metadata{Rasters.NCDfile, Dict{String, Any}}, Missing}, data::Char, dims::Tuple{}, refdims::Tuple{}, name::Symbol, metadata::DimensionalData.Dimensions.LookupArrays.Metad
ata{Rasters.NCDfile, Dict{String, Any}}, missingval::Missing)                                                                                                                                   
    @ Rasters ~/.julia/packages/Rasters/U9GgU/src/array.jl:105                                                                                                                                  
  [2] rebuild(A::Raster{Char, 0, Tuple{}, Tuple{}, CommonDataModel.CFVariable{Char, 0, NCDatasets.Variable{Char, 0, NCDatasets.NCDataset{Nothing}}, NCDatasets.Attributes{NCDatasets.NCDataset{N
othing}}, NamedTuple{(:fillvalue, :missing_values, :scale_factor, :add_offset, :calendar, :time_origin, :time_factor), Tuple{Nothing, Tuple{}, Vararg{Nothing, 5}}}}, Symbol, DimensionalData.Di
mensions.LookupArrays.Metadata{Rasters.NCDfile, Dict{String, Any}}, Missing}, data::Char, dims::Tuple{}, refdims::Tuple{}, name::Symbol, metadata::DimensionalData.Dimensions.LookupArrays.Metad
ata{Rasters.NCDfile, Dict{String, Any}})                                                                                                                                                        
    @ Rasters ~/.julia/packages/Rasters/U9GgU/src/array.jl:105                                                                                                                                  
  [3] rebuild (repeats 4 times)                                                                                                                                                                 
    @ ~/.julia/packages/DimensionalData/pS9IE/src/array/array.jl:52 [inlined]                                                                                                                   
  [4] modify(f::Type{Array}, A::Raster{Char, 0, Tuple{}, Tuple{}, CommonDataModel.CFVariable{Char, 0, NCDatasets.Variable{Char, 0, NCDatasets.NCDataset{Nothing}}, NCDatasets.Attributes{NCDatas
ets.NCDataset{Nothing}}, NamedTuple{(:fillvalue, :missing_values, :scale_factor, :add_offset, :calendar, :time_origin, :time_factor), Tuple{Nothing, Tuple{}, Vararg{Nothing, 5}}}}, Symbol, Dim
ensionalData.Dimensions.LookupArrays.Metadata{Rasters.NCDfile, Dict{String, Any}}, Missing})                                                                                                    
    @ Rasters ~/.julia/packages/Rasters/U9GgU/src/array.jl:123                                                                                                                                  
  [5] (::Rasters.var"#98#100"{UnionAll})(a::Raster{Char, 0, Tuple{}, Tuple{}, CommonDataModel.CFVariable{Char, 0, NCDatasets.Variable{Char, 0, NCDatasets.NCDataset{Nothing}}, NCDatasets.Attrib
utes{NCDatasets.NCDataset{Nothing}}, NamedTuple{(:fillvalue, :missing_values, :scale_factor, :add_offset, :calendar, :time_origin, :time_factor), Tuple{Nothing, Tuple{}, Vararg{Nothing, 5}}}},
 Symbol, DimensionalData.Dimensions.LookupArrays.Metadata{Rasters.NCDfile, Dict{String, Any}}, Missing})                                                                                        
    @ Rasters ~/.julia/packages/Rasters/U9GgU/src/stack.jl:326                                  
  [6] map(f::Rasters.var"#98#100"{UnionAll}, t::Tuple{Raster{Char, 0, Tuple{}, Tuple{}, CommonDataModel.CFVariable{Char, 0, NCDatasets.Variable{Char, 0, NCDatasets.NCDataset{Nothing}},[96/485]
ets.Attributes{NCDatasets.NCDataset{Nothing}}, NamedTuple{(:fillvalue, :missing_values, :scale_factor, :add_offset, :calendar, :time_origin, :time_factor), Tuple{Nothing, Tuple{}, Vararg{Nothi
ng, 5}}}}, Symbol, DimensionalData.Dimensions.LookupArrays.Metadata{Rasters.NCDfile, Dict{String, Any}}, Missing}, Raster{Int8, 2, Tuple{X{Mapped{Int32, Vector{Int32}, DimensionalData.Dimensio
ns.LookupArrays.ForwardOrdered, DimensionalData.Dimensions.LookupArrays.Regular{Int32}, DimensionalData.Dimensions.LookupArrays.Points, DimensionalData.Dimensions.LookupArrays.Metadata{Rasters
.NCDfile, Dict{String, Any}}, EPSG, EPSG, X{Colon}}}, Y{Mapped{Int32, Vector{Int32}, DimensionalData.Dimensions.LookupArrays.ReverseOrdered, DimensionalData.Dimensions.LookupArrays.Regular{Int
32}, DimensionalData.Dimensions.LookupArrays.Points, DimensionalData.Dimensions.LookupArrays.Metadata{Rasters.NCDfile, Dict{String, Any}}, EPSG, EPSG, Y{Colon}}}}, Tuple{}, CommonDataModel.CFV
ariable{Int8, 2, NCDatasets.Variable{Int8, 2, NCDatasets.NCDataset{Nothing}}, NCDatasets.Attributes{NCDatasets.NCDataset{Nothing}}, NamedTuple{(:fillvalue, :missing_values, :scale_factor, :add
_offset, :calendar, :time_origin, :time_factor), Tuple{Nothing, Tuple{}, Vararg{Nothing, 5}}}}, Symbol, DimensionalData.Dimensions.LookupArrays.Metadata{Rasters.NCDfile, Dict{String, Any}}, Mi
ssing}, Raster{Float32, 2, Tuple{X{Mapped{Int32, Vector{Int32}, DimensionalData.Dimensions.LookupArrays.ForwardOrdered, DimensionalData.Dimensions.LookupArrays.Regular{Int32}, DimensionalData.
Dimensions.LookupArrays.Points, DimensionalData.Dimensions.LookupArrays.Metadata{Rasters.NCDfile, Dict{String, Any}}, EPSG, EPSG, X{Colon}}}, Y{Mapped{Int32, Vector{Int32}, DimensionalData.Dim
ensions.LookupArrays.ReverseOrdered, DimensionalData.Dimensions.LookupArrays.Regular{Int32}, DimensionalData.Dimensions.LookupArrays.Points, DimensionalData.Dimensions.LookupArrays.Metadata{Ra
sters.NCDfile, Dict{String, Any}}, EPSG, EPSG, Y{Colon}}}}, Tuple{}, CommonDataModel.CFVariable{Float32, 2, NCDatasets.Variable{Float32, 2, NCDatasets.NCDataset{Nothing}}, NCDatasets.Attribute
s{NCDatasets.NCDataset{Nothing}}, NamedTuple{(:fillvalue, :missing_values, :scale_factor, :add_offset, :calendar, :time_origin, :time_factor), Tuple{Nothing, Tuple{}, Vararg{Nothing, 5}}}}, Sy
mbol, DimensionalData.Dimensions.LookupArrays.Metadata{Rasters.NCDfile, Dict{String, Any}}, Missing}, Raster{Float32, 2, Tuple{X{Mapped{Int32, Vector{Int32}, DimensionalData.Dimensions.LookupA
rrays.ForwardOrdered, DimensionalData.Dimensions.LookupArrays.Regular{Int32}, DimensionalData.Dimensions.LookupArrays.Points, DimensionalData.Dimensions.LookupArrays.Metadata{Rasters.NCDfile, 
Dict{String, Any}}, EPSG, EPSG, X{Colon}}}, Y{Mapped{Int32, Vector{Int32}, DimensionalData.Dimensions.LookupArrays.ReverseOrdered, DimensionalData.Dimensions.LookupArrays.Regular{Int32}, Dimen
sionalData.Dimensions.LookupArrays.Points, DimensionalData.Dimensions.LookupArrays.Metadata{Rasters.NCDfile, Dict{String, Any}}, EPSG, EPSG, Y{Colon}}}}, Tuple{}, CommonDataModel.CFVariable{Fl
oat32, 2, NCDatasets.Variable{Float32, 2, NCDatasets.NCDataset{Nothing}}, NCDatasets.Attributes{NCDatasets.NCDataset{Nothing}}, NamedTuple{(:fillvalue, :missing_values, :scale_factor, :add_off
set, :calendar, :time_origin, :time_factor), Tuple{Nothing, Tuple{}, Vararg{Nothing, 5}}}}, Symbol, DimensionalData.Dimensions.LookupArrays.Metadata{Rasters.NCDfile, Dict{String, Any}}, Missin
g}, Raster{Float32, 2, Tuple{X{Mapped{Int32, Vector{Int32}, DimensionalData.Dimensions.LookupArrays.ForwardOrdered, DimensionalData.Dimensions.LookupArrays.Regular{Int32}, DimensionalData.Dime
nsions.LookupArrays.Points, DimensionalData.Dimensions.LookupArrays.Metadata{Rasters.NCDfile, Dict{String, Any}}, EPSG, EPSG, X{Colon}}}, Y{Mapped{Int32, Vector{Int32}, DimensionalData.Dimensi
ons.LookupArrays.ReverseOrdered, DimensionalData.Dimensions.LookupArrays.Regular{Int32}, DimensionalData.Dimensions.LookupArrays.Points, DimensionalData.Dimensions.LookupArrays.Metadata{Raster
s.NCDfile, Dict{String, Any}}, EPSG, EPSG, Y{Colon}}}}, Tuple{}, CommonDataModel.CFVariable{Float32, 2, NCDatasets.Variable{Float32, 2, NCDatasets.NCDataset{Nothing}}, NCDatasets.Attributes{NC
Datasets.NCDataset{Nothing}}, NamedTuple{(:fillvalue, :missing_values, :scale_factor, :add_offset, :calendar, :time_origin, :time_factor), Tuple{Nothing, Tuple{}, Vararg{Nothing, 5}}}}, Symbol
, DimensionalData.Dimensions.LookupArrays.Metadata{Rasters.NCDfile, Dict{String, Any}}, Missing}, Raster{Union{Missing, Float32}, 2, Tuple{X{Mapped{Int32, Vector{Int32}, DimensionalData.Dimens
ions.LookupArrays.ForwardOrdered, DimensionalData.Dimensions.LookupArrays.Regular{Int32}, DimensionalData.Dimensions.LookupArrays.Points, DimensionalData.Dimensions.LookupArrays.Metadata{Raste
rs.NCDfile, Dict{String, Any}}, EPSG, EPSG, X{Colon}}}, Y{Mapped{Int32, Vector{Int32}, DimensionalData.Dimensions.LookupArrays.ReverseOrdered, DimensionalData.Dimensions.LookupArrays.Regular{I
nt32}, DimensionalData.Dimensions.LookupArrays.Points, DimensionalData.Dimensions.LookupArrays.Metadata{Rasters.NCDfile, Dict{String, Any}}, EPSG, EPSG, Y{Colon}}}}, Tuple{}, CommonDataModel.C
FVariable{Union{Missing, Float32}, 2, NCDatasets.Variable{Float32, 2, NCDatasets.NCDataset{Nothing}}, NCDatasets.Attributes{NCDatasets.NCDataset{Nothing}}, NamedTuple{(:fillvalue, :missing_val
ues, :scale_factor, :add_offset, :calendar, :time_origin, :time_factor), Tuple{Float32, Tuple{}, Vararg{Nothing, 5}}}}, Symbol, DimensionalData.Dimensions.LookupArrays.Metadata{Rasters.NCDfile
, Dict{String, Any}}, Missing}, Raster{Union{Missing, Int16}, 2, Tuple{X{Mapped{Int32, Vector{Int32}, DimensionalData.Dimensions.LookupArrays.ForwardOrdered, DimensionalData.Dimensions.LookupA
rrays.Regular{Int32}, DimensionalData.Dimensions.LookupArrays.Points, DimensionalData.Dimensions.LookupArrays.Metadata{Rasters.NCDfile, Dict{String, Any}}, EPSG, EPSG, X{Colon}}}, Y{Mapped{Int
32, Vector{Int32}, DimensionalData.Dimensions.LookupArrays.ReverseOrdered, DimensionalData.Dimensions.LookupArrays.Regular{Int32}, DimensionalData.Dimensions.LookupArrays.Points, DimensionalDa
ta.Dimensions.LookupArrays.Metadata{Rasters.NCDfile, Dict{String, Any}}, EPSG, EPSG, Y{Colon}}}}, Tuple{}, CommonDataModel.CFVariable{Union{Missing, Int16}, 2, NCDatasets.Variable{Int16, 2, NC
Datasets.NCDataset{Nothing}}, NCDatasets.Attributes{NCDatasets.NCDataset{Nothing}}, NamedTuple{(:fillvalue, :missing_values, :scale_factor, :add_offset, :calendar, :time_origin, :time_factor),
 Tuple{Int16, Tuple{}, Vararg{Nothing, 5}}}}, Symbol, DimensionalData.Dimensions.LookupArrays.Metadata{Rasters.NCDfile, Dict{String, Any}}, Missing}, Raster{Int8, 2, Tuple{X{Mapped{Int32, Vect
or{Int32}, DimensionalData.Dimensions.LookupArrays.ForwardOrdered, DimensionalData.Dimensions.LookupArrays.Regular{Int32}, DimensionalData.Dimensions.LookupArrays.Points, DimensionalData.Dimen
sions.LookupArrays.Metadata{Rasters.NCDfile, Dict{String, Any}}, EPSG, EPSG, X{Colon}}}, Y{Mapped{Int32, Vector{Int32}, DimensionalData.Dimensions.LookupArrays.ReverseOrdered, DimensionalData.
Dimensions.LookupArrays.Regular{Int32}, DimensionalData.Dimensions.LookupArrays.Points, DimensionalData.Dimensions.LookupArrays.Metadata{Rasters.NCDfile, Dict{String, Any}}, EPSG, EPSG, Y{Colo
n}}}}, Tuple{}, CommonDataModel.CFVariable{Int8, 2, NCDatasets.Variable{Int8, 2, NCDatasets.NCDataset{Nothing}}, NCDatasets.Attributes{NCDatasets.NCDataset{Nothing}}, NamedTuple{(:fillvalue, :
missing_values, :scale_factor, :add_offset, :calendar, :time_origin, :time_factor), Tuple{Nothing, Tuple{}, Vararg{Nothing, 5}}}}, Symbol, DimensionalData.Dimensions.LookupArrays.Metadata{Rast
ers.NCDfile, Dict{String, Any}}, Missing}, Raster{Int16, 2, Tuple{X{Mapped{Int32, Vector{Int32}, DimensionalData.Dimensions.LookupArrays.ForwardOrdered, DimensionalData.Dimensions.LookupArrays
.Regular{Int32}, DimensionalData.Dimensions.LookupArrays.Points, DimensionalData.Dimensions.LookupArrays.Metadata{Rasters.NCDfile, Dict{String, Any}}, EPSG, EPSG, X{Colon}}}, Y{Mapped{Int32, V
ector{Int32}, DimensionalData.Dimensions.LookupArrays.ReverseOrdered, DimensionalData.Dimensions.LookupArrays.Regular{Int32}, DimensionalData.Dimensions.LookupArrays.Points, DimensionalData.Di
mensions.LookupArrays.Metadata{Rasters.NCDfile, Dict{String, Any}}, EPSG, EPSG, Y{Colon}}}}, Tuple{}, CommonDataModel.CFVariable{Int16, 2, NCDatasets.Variable{Int16, 2, NCDatasets.NCDataset{No
thing}}, NCDatasets.Attributes{NCDatasets.NCDataset{Nothing}}, NamedTuple{(:fillvalue, :missing_values, :scale_factor, :add_offset, :calendar, :time_origin, :time_factor), Tuple{Nothing, Tuple
{}, Vararg{Nothing, 5}}}}, Symbol, DimensionalData.Dimensions.LookupArrays.Metadata{Rasters.NCDfile, Dict{String, Any}}, Missing}})
    @ Base ./tuple.jl:276
  [8] #97
    @ ~/.julia/packages/Rasters/U9GgU/src/stack.jl:326 [inlined]
  [9] #open#101
    @ ~/.julia/packages/Rasters/U9GgU/src/stack.jl:333 [inlined]
 [10] open
    @ ~/.julia/packages/Rasters/U9GgU/src/stack.jl:331 [inlined]
 [11] modify(f::Type, s::RasterStack{Rasters.FileStack{Rasters.NCDfile, (:mapping, :mask, :firn, :surface, :thickness, :bed, :errbed, :source, :geoid), String, NTuple{9, Union}, Tuple{Tuple{},
 Vararg{Tuple{Int64, Int64}, 8}}, Tuple{DiskArrays.GridChunks{0}, Vararg{DiskArrays.GridChunks{2}, 8}}, NTuple{9, DiskArrays.Unchunked}}, Tuple{X{Mapped{Int32, Vector{Int32}, DimensionalData.D
imensions.LookupArrays.ForwardOrdered, DimensionalData.Dimensions.LookupArrays.Regular{Int32}, DimensionalData.Dimensions.LookupArrays.Points, DimensionalData.Dimensions.LookupArrays.Metadata{
Rasters.NCDfile, Dict{String, Any}}, EPSG, EPSG, X{Colon}}}, Y{Mapped{Int32, Vector{Int32}, DimensionalData.Dimensions.LookupArrays.ReverseOrdered, DimensionalData.Dimensions.LookupArrays.Regu
lar{Int32}, DimensionalData.Dimensions.LookupArrays.Points, DimensionalData.Dimensions.LookupArrays.Metadata{Rasters.NCDfile, Dict{String, Any}}, EPSG, EPSG, Y{Colon}}}}, Tuple{}, NamedTuple{(
:mapping, :mask, :firn, :surface, :thickness, :bed, :errbed, :source, :geoid), Tuple{Tuple{}, Vararg{Tuple{X{Colon}, Y{Colon}}, 8}}}, DimensionalData.Dimensions.LookupArrays.Metadata{Rasters.N
CDfile, Dict{String, Any}}, NamedTuple{(:mapping, :mask, :firn, :surface, :thickness, :bed, :errbed, :source, :geoid), NTuple{9, DimensionalData.Dimensions.LookupArrays.Metadata{Rasters.NCDfil
e, Dict{String, Any}}}}, Missing})
    @ Rasters ~/.julia/packages/Rasters/U9GgU/src/stack.jl:325
 [12] read(x::RasterStack{Rasters.FileStack{Rasters.NCDfile, (:mapping, :mask, :firn, :surface, :thickness, :bed, :errbed, :source, :geoid), String, NTuple{9, Union}, Tuple{Tuple{}, Vararg{Tup
le{Int64, Int64}, 8}}, Tuple{DiskArrays.GridChunks{0}, Vararg{DiskArrays.GridChunks{2}, 8}}, NTuple{9, DiskArrays.Unchunked}}, Tuple{X{Mapped{Int32, Vector{Int32}, DimensionalData.Dimensions.L
ookupArrays.ForwardOrdered, DimensionalData.Dimensions.LookupArrays.Regular{Int32}, DimensionalData.Dimensions.LookupArrays.Points, DimensionalData.Dimensions.LookupArrays.Metadata{Rasters.NCD
file, Dict{String, Any}}, EPSG, EPSG, X{Colon}}}, Y{Mapped{Int32, Vector{Int32}, DimensionalData.Dimensions.LookupArrays.ReverseOrdered, DimensionalData.Dimensions.LookupArrays.Regular{Int32},
 DimensionalData.Dimensions.LookupArrays.Points, DimensionalData.Dimensions.LookupArrays.Metadata{Rasters.NCDfile, Dict{String, Any}}, EPSG, EPSG, Y{Colon}}}}, Tuple{}, NamedTuple{(:mapping, :
mask, :firn, :surface, :thickness, :bed, :errbed, :source, :geoid), Tuple{Tuple{}, Vararg{Tuple{X{Colon}, Y{Colon}}, 8}}}, DimensionalData.Dimensions.LookupArrays.Metadata{Rasters.NCDfile, Dic
t{String, Any}}, NamedTuple{(:mapping, :mask, :firn, :surface, :thickness, :bed, :errbed, :source, :geoid), NTuple{9, DimensionalData.Dimensions.LookupArrays.Metadata{Rasters.NCDfile, Dict{Str
ing, Any}}}}, Missing})
    @ Rasters ~/.julia/packages/Rasters/U9GgU/src/read.jl:9
 [13] RasterStack(filename::String; dims::Nothing, refdims::Tuple{}, metadata::Nothing, crs::Nothing, mappedcrs::Nothing, layerdims::Nothing, layermetadata::Nothing, missingval::Nothing, sourc
e::Type, name::Nothing, keys::Nothing, layersfrom::Nothing, resize::Nothing, lazy::Bool, ext::Nothing)
    @ Rasters ~/.julia/packages/Rasters/U9GgU/src/stack.jl:286
 [14] RasterStack(filename::String)
    @ Rasters ~/.julia/packages/Rasters/U9GgU/src/stack.jl:241
 [15] top-level scope
    @ REPL[2]:1

[rafaqz]

Ok the short term fix is to use lazy=true and just avoid loading that variable.

r = RasterStack("nc.nc"; lazy=true)                                                                                                                                                                     

Long term I need to look for grid_mapping attributes and ignore the variable they point to, which is mapping here. This is the same as for ignoring bounds variables of dimensions.

I think this got through in the past because lazy=true was the default behaviour.

[rafaqz]

I have a fix whenever github is up for pushing again.

But if you have a smaller file or know how to make a file with grid_mapping using NCDatasets.jl it would be good to be able to write a test for this.

[mauro3]

Converting this a file t.txt with this content

netcdf tt {
dimensions:
        y = 1 ;
        x = 1 ;
variables:
        char mapping ;
                mapping:grid_mapping_name = "polar_stereographic" ;
                mapping:latitude_of_projection_origin = -90. ;
                mapping:standard_parallel = -71. ;
                mapping:straight_vertical_longitude_from_pole = 0. ;
                mapping:semi_major_axis = 6378273. ;
                mapping:inverse_flattening = 298.27940504282 ;
                mapping:false_easting = 0. ;
                mapping:false_northing = 0. ;
        byte mask(y, x) ;
                mask:long_name = "mask" ;
                mask:grid_mapping = "mapping" ;
                mask:valid_range = 0b, 4b ;
                mask:flag_values = 0b, 1b, 2b, 3b, 4b ;

// global attributes:

data:

 mapping = "" ;

 mask =
  0 ;
}

into an ncfile with

ncgen t.txt -o nc.nc

produces a file which errors.

[rafaqz]

Thanks