iconarray.core.utilities.ind_from_latlon#

iconarray.core.utilities.ind_from_latlon(lon_array: xarray.DataArray, lat_array: xarray.DataArray, lon_point: float, lat_point: float, n: int = 1, verbose: bool = False) → List[int]#

Find the indices of the n closest cells in a grid, relative to a given latitude/longitude point.

The function builds a BallTree from the provided 1D or 2D array of longitude and latitude coordinates, and queries it to find the n nearest neighbors to the given point.

Parameters:

  • lon_array (xr.DataArray) – A 1D or 2D xr of longitude values [degree].

  • lat_array (xr.DataArray) – A 1D or 2D xr of latitude values [degree].

  • lon_point (float) – The longitude value [degree] of the point to find the closest point(s) to.

  • lat_point (float) – The latitude value [degree] of the point to find the closest point(s) to.

  • n (int, optional) – The number of closest points to return. Default is 1.

  • verbose (bool, optional) – Print information. Defaults to False.

Returns:

List[int] – The indices of the closest n points to the given point.

Example

>>> # Get values of grid cell closest to coordinate
>>> # E.g. Zürich:
>>> lon = 8.54
>>> lat = 47.38
>>> lats = ds.clat
>>> lons = ds.clon
>>> if ds.clat.attrs.get('units') == 'radian':
>>>     lats = np.rad2deg(lats)
>>>     lons = np.rad2deg(lons)
>>> ind = iconarray.ind_from_latlon(
...         lats,lons,lat,lon,
...         verbose=True, n=1
...         )

>>> ind
3352
# Closest ind: 3352
# Given lat: 47.380 deg. Closest 1 lat/s found: 47.372
# Given lon: 8.540 deg. Closest 1 lon/s found: 8.527