AssertionError when using FieldSet with no variations in velocity field with time

[mathildejutras]

Hello,
I am trying to launch particles from a list using a constant velocity field, so without any time component. I was able to do it with other velocity data in the same format and with pretty much the same script, so I don't understand what is causing my error.

I get this error :
AssertionError: Field U expecting a data shape of [tdim, ydim, xdim]. Flag transpose=True could help to reorder the data.

But I don't have a time dimension. I would expect the algorithm simply uses the velocities as fixed in time in that case (as they did in the past for me).

Here's my script:
`file = '../../Subdatasets/SO_netcdf/Vel_SO.nc'

#Setting up the fieldset we will create using our data
file_names ={'U':file,
'V':file}
variables = {'U':'ugeo',
'V':'vgeo'}
dimensions = {'lat':'lat',
'lon':'lon'}

print('Create particle set')
fset = FieldSet.from_netcdf(file,variables,dimensions)

Here's what file content looks like:
<xarray.Dataset>
Dimensions: (lon: 360, lat: 65)
Coordinates:
* lon (lon) float32 0.5 1.5 2.5 3.5 4.5 ... 355.5 356.5 357.5 358.5 359.5
* lat (lat) float32 -64.5 -63.5 -62.5 -61.5 -60.5 ... -3.5 -2.5 -1.5 -0.5
Data variables:
ugeo (lon, lat) float64 nan nan nan nan ... 0.008358 -0.01001 nan
vgeo (lon, lat) float64 nan nan nan nan nan nan ... nan nan nan nan nan

[mathildejutras]

If someone every gets the same error, it turns out that inversing the order of the lon and lat dimensions in the dataset works.