.. DO NOT EDIT.
.. THIS FILE WAS AUTOMATICALLY GENERATED BY SPHINX-GALLERY.
.. TO MAKE CHANGES, EDIT THE SOURCE PYTHON FILE:
.. "gallery/example_model_along_trajectory.py"
.. LINE NUMBERS ARE GIVEN BELOW.

.. only:: html

    .. note::
        :class: sphx-glr-download-link-note

        :ref:`Go to the end <sphx_glr_download_gallery_example_model_along_trajectory.py>`
        to download the full example code.

.. rst-class:: sphx-glr-example-title

.. _sphx_glr_gallery_example_model_along_trajectory.py:


Read variables from a model along the trajectories of drifters.
=============================================================================

.. GENERATED FROM PYTHON SOURCE LINES 5-15

.. code-block:: Python


    import xarray as xr
    import numpy as np
    import cf_xarray as _
    import pyproj
    import trajan as ta
    import matplotlib.pyplot as plt

    print(ta.versions())





.. rst-class:: sphx-glr-script-out

 .. code-block:: none


    ------------------------------------------------------
    Software and hardware:
      TrajAn version 0.0.0
      Platform: Linux, 6.17.0-1022-azure
      15.614940643310547 GB memory
      4 processors (x86_64)
      NumPy version 2.5.2
      SciPy version 1.18.0
      Matplotlib version 3.11.1
      NetCDF4 version 1.7.4
      Xarray version 2025.9.0
      Pandas version 3.0.5
      OpenDrift version 1.14.10
      Python version 3.14.6 | packaged by conda-forge | (main, Aug 11 2026, 10:26:15) [GCC 14.4.0]
    ------------------------------------------------------





.. GENERATED FROM PYTHON SOURCE LINES 16-17

Open drifter dataset from a CSV file

.. GENERATED FROM PYTHON SOURCE LINES 17-24

.. code-block:: Python

    ds = ta.read_csv(ta.DATA_DIR + 'omb/bug05_pos.csv',
                     lon='Longitude',
                     lat='Latitude',
                     time='Time',
                     name='Device')
    print(ds)





.. rst-class:: sphx-glr-script-out

 .. code-block:: none

    2026-08-24 11:11:03 runnervm76f27 trajan.accessor[2752] DEBUG Detecting trajectory dimension
    2026-08-24 11:11:03 runnervm76f27 trajan.accessor[2752] DEBUG No trajectory_id attribute/variable found, trying to identify by name.
    2026-08-24 11:11:03 runnervm76f27 trajan.accessor[2752] DEBUG Detecting time-variable for "obs"..
    2026-08-24 11:11:03 runnervm76f27 trajan.accessor[2752] WARNING No time CF-variable with dimension obs
    2026-08-24 11:11:03 runnervm76f27 trajan.accessor[2752] WARNING Found instead variable with time in name: time
    2026-08-24 11:11:03 runnervm76f27 trajan.accessor[2752] DEBUG Detected obs-dim: obs, detected time-variable: time.
    2026-08-24 11:11:03 runnervm76f27 trajan.accessor[2752] DEBUG Detected Ragged trajectory dataset
    2026-08-24 11:11:03 runnervm76f27 trajan.traj.ragged[2752] DEBUG Condensing 844 observations.
    2026-08-24 11:11:03 runnervm76f27 trajan.traj.ragged[2752] DEBUG Condensed observations from: 844 to 844
    2026-08-24 11:11:03 runnervm76f27 trajan.accessor[2752] DEBUG Detecting trajectory dimension
    2026-08-24 11:11:03 runnervm76f27 trajan.accessor[2752] DEBUG No trajectory_id attribute/variable found, trying to identify by name.
    2026-08-24 11:11:03 runnervm76f27 trajan.accessor[2752] DEBUG Detecting time-variable for "obs"..
    2026-08-24 11:11:03 runnervm76f27 trajan.accessor[2752] WARNING No time CF-variable with dimension obs
    2026-08-24 11:11:03 runnervm76f27 trajan.accessor[2752] WARNING Found instead variable with time in name: time
    2026-08-24 11:11:03 runnervm76f27 trajan.accessor[2752] DEBUG Detected obs-dim: obs, detected time-variable: time.
    2026-08-24 11:11:03 runnervm76f27 trajan.accessor[2752] DEBUG Detected Ragged trajectory dataset
    <xarray.Dataset> Size: 20kB
    Dimensions:     (trajectory: 1, obs: 844)
    Coordinates:
      * trajectory  (trajectory) <U18 72B 'dev864475040536665'
      * obs         (obs) int64 7kB 0 1 2 3 4 5 6 7 ... 837 838 839 840 841 842 843
    Data variables:
        time        (trajectory, obs) datetime64[us] 7kB 2022-05-10T12:56:16.5000...
        lon         (trajectory, obs) float32 3kB 5.332 5.332 5.332 ... 5.25 5.25
        lat         (trajectory, obs) float32 3kB 60.38 60.38 60.38 ... 60.45 60.45
    Attributes:
        Conventions:          CF-1.10
        featureType:          trajectory
        geospatial_lat_min:   60.383804
        geospatial_lat_max:   60.45141
        geospatial_lon_min:   5.2444935
        geospatial_lon_max:   5.33242
        time_coverage_start:  2020-01-01T00:00:07.250000
        time_coverage_end:    2022-05-20T11:03:46.120000




.. GENERATED FROM PYTHON SOURCE LINES 25-26

Open the Norkyst800 model

.. GENERATED FROM PYTHON SOURCE LINES 26-29

.. code-block:: Python

    nk = xr.open_dataset(
        'https://thredds.met.no/thredds/dodsC/sea/norkyst800m/1h/aggregate_be')








.. GENERATED FROM PYTHON SOURCE LINES 30-31

Use cf-xarray to get the CRS

.. GENERATED FROM PYTHON SOURCE LINES 31-35

.. code-block:: Python

    gm = nk.cf['grid_mapping']
    nk_crs = pyproj.CRS.from_cf(gm.attrs)
    print(nk_crs)





.. rst-class:: sphx-glr-script-out

 .. code-block:: none

    2026-08-24 11:11:10 runnervm76f27 pyproj[2752] DEBUG PROJ_ERROR: proj_create: several objects matching this name: Krovak (Greenwich), Equal Earth Greenwich, Laborde Grid (Greenwich), Modified Krovak (Greenwich), Krovak East North (Greenwich), Modified Krovak East North (Greenwich), ...
    {"$schema": "https://proj.org/schemas/v0.2/projjson.schema.json", "type": "ProjectedCRS", "name": "undefined", "base_crs": {"$schema": "https://proj.org/schemas/v0.7/projjson.schema.json", "type": "GeographicCRS", "name": "undefined", "datum": {"type": "GeodeticReferenceFrame", "name": "undefined", "ellipsoid": {"name": "undefined", "semi_major_axis": 6378137, "semi_minor_axis": 6356752.3142}}, "coordinate_system": {"subtype": "ellipsoidal", "axis": [{"name": "Longitude", "abbreviation": "lon", "direction": "east", "unit": "degree"}, {"name": "Latitude", "abbreviation": "lat", "direction": "north", "unit": "degree"}]}}, "conversion": {"$schema": "https://proj.org/schemas/v0.7/projjson.schema.json", "type": "Conversion", "name": "unknown", "method": {"name": "Polar Stereographic (variant B)", "id": {"authority": "EPSG", "code": 9829}}, "parameters": [{"name": "Latitude of standard parallel", "value": 60, "unit": "degree", "id": {"authority": "EPSG", "code": 8832}}, {"name": "Longitude of origin", "value": 70, "unit": "degree", "id": {"authority": "EPSG", "code": 8833}}, {"name": "False easting", "value": 3192800, "unit": "metre", "id": {"authority": "EPSG", "code": 8806}}, {"name": "False northing", "value": 1784000, "unit": "metre", "id": {"authority": "EPSG", "code": 8807}}]}, "coordinate_system": {"$schema": "https://proj.org/schemas/v0.7/projjson.schema.json", "type": "CoordinateSystem", "subtype": "Cartesian", "axis": [{"name": "Easting", "abbreviation": "E", "direction": "east", "unit": "metre"}, {"name": "Northing", "abbreviation": "N", "direction": "north", "unit": "metre"}]}}




.. GENERATED FROM PYTHON SOURCE LINES 36-37

Grid the drifter dataset to the timesteps of the model.

.. GENERATED FROM PYTHON SOURCE LINES 37-43

.. code-block:: Python

    times = nk.sel(time=slice('2022-05-10', '2022-05-20')).time.values
    ds = ds.traj.gridtime(times)
    ds = ds.dropna('time', how='all')

    print(ds)





.. rst-class:: sphx-glr-script-out

 .. code-block:: none

    2026-08-24 11:11:10 runnervm76f27 trajan.accessor[2752] DEBUG Detecting trajectory dimension
    2026-08-24 11:11:10 runnervm76f27 trajan.accessor[2752] DEBUG Found CF trajectory dimension "trajectory"
    2026-08-24 11:11:10 runnervm76f27 trajan.accessor[2752] DEBUG Detecting time-variable for "obs"..
    2026-08-24 11:11:10 runnervm76f27 trajan.accessor[2752] WARNING No time CF-variable with dimension obs
    2026-08-24 11:11:10 runnervm76f27 trajan.accessor[2752] WARNING Found instead variable with time in name: time
    2026-08-24 11:11:10 runnervm76f27 trajan.accessor[2752] DEBUG Detected obs-dim: obs, detected time-variable: time.
    2026-08-24 11:11:10 runnervm76f27 trajan.accessor[2752] DEBUG Detected Ragged trajectory dataset
    2026-08-24 11:11:10 runnervm76f27 trajan.accessor[2752] DEBUG Detecting trajectory dimension
    2026-08-24 11:11:10 runnervm76f27 trajan.accessor[2752] DEBUG Found CF trajectory dimension "trajectory"
    2026-08-24 11:11:10 runnervm76f27 trajan.accessor[2752] DEBUG Detecting time-variable for "obs"..
    2026-08-24 11:11:10 runnervm76f27 trajan.accessor[2752] WARNING No time CF-variable with dimension obs
    2026-08-24 11:11:10 runnervm76f27 trajan.accessor[2752] WARNING Found instead variable with time in name: time
    2026-08-24 11:11:10 runnervm76f27 trajan.accessor[2752] DEBUG Detected obs-dim: obs, detected time-variable: time.
    2026-08-24 11:11:10 runnervm76f27 trajan.accessor[2752] DEBUG Detected Ragged trajectory dataset
    2026-08-24 11:11:10 runnervm76f27 trajan.accessor[2752] DEBUG Detecting trajectory dimension
    2026-08-24 11:11:10 runnervm76f27 trajan.accessor[2752] DEBUG Found CF trajectory dimension "trajectory"
    2026-08-24 11:11:10 runnervm76f27 trajan.accessor[2752] DEBUG Detected obs-dim: time, detected time-variable: time.
    2026-08-24 11:11:10 runnervm76f27 trajan.accessor[2752] DEBUG Detected Orthogonal trajectory dataset
    2026-08-24 11:11:10 runnervm76f27 trajan.traj.orthogonal[2752] WARNING non-unique time points, dropping time-duplicates
    <xarray.Dataset> Size: 6kB
    Dimensions:     (trajectory: 1, time: 251)
    Coordinates:
      * time        (time) datetime64[us] 2kB 2022-05-10T13:00:00 ... 2022-05-20T...
      * trajectory  (trajectory) <U18 72B 'dev864475040536665'
    Data variables:
        lon         (trajectory, time) float64 2kB 5.332 5.332 5.332 ... 5.25 5.25
        lat         (trajectory, time) float64 2kB 60.38 60.38 60.38 ... 60.45 60.45
    Attributes:
        Conventions:          CF-1.10
        featureType:          trajectory
        geospatial_lat_min:   60.383804
        geospatial_lat_max:   60.45141
        geospatial_lon_min:   5.2444935
        geospatial_lon_max:   5.33242
        time_coverage_start:  2020-01-01T00:00:07.250000
        time_coverage_end:    2022-05-20T11:03:46.120000




.. GENERATED FROM PYTHON SOURCE LINES 44-45

Transform the drifter dataset to the CRS of the model

.. GENERATED FROM PYTHON SOURCE LINES 45-48

.. code-block:: Python

    dst = ds.traj.transform(nk_crs)
    print(dst.x)





.. rst-class:: sphx-glr-script-out

 .. code-block:: none

    2026-08-24 11:11:10 runnervm76f27 trajan.accessor[2752] DEBUG Detecting trajectory dimension
    2026-08-24 11:11:10 runnervm76f27 trajan.accessor[2752] DEBUG Found CF trajectory dimension "trajectory"
    2026-08-24 11:11:10 runnervm76f27 trajan.accessor[2752] DEBUG Detected obs-dim: time, detected time-variable: time.
    2026-08-24 11:11:10 runnervm76f27 trajan.accessor[2752] DEBUG Detected Orthogonal trajectory dataset
    2026-08-24 11:11:10 runnervm76f27 trajan.accessor[2752] DEBUG Detecting trajectory dimension
    2026-08-24 11:11:10 runnervm76f27 trajan.accessor[2752] DEBUG Found CF trajectory dimension "trajectory"
    2026-08-24 11:11:10 runnervm76f27 trajan.accessor[2752] DEBUG Detected obs-dim: time, detected time-variable: time.
    2026-08-24 11:11:10 runnervm76f27 trajan.accessor[2752] DEBUG Detected Orthogonal trajectory dataset
    <xarray.DataArray 'x' (trajectory: 1, time: 251)> Size: 2kB
    array([[341742.46508359, 341746.15575471, 341750.41008676,
            341754.66443019, 341758.918785  , 341763.17315118,
            341767.42752874, 341771.68191768, 341775.93631799,
            341780.19072968, 341784.44515275, 341788.69958719,
            341792.95403301, 341797.2084902 , 341801.46295877,
            341805.71743872, 341809.97193004, 341814.22643274,
            341818.48094681, 341822.73547226, 341826.99000909,
            341831.24455729, 341835.49911687, 341839.75368782,
            341844.00827015, 341848.26286386, 341852.51746894,
            341856.7720854 , 341861.02671323, 341865.28135244,
            341869.53600302, 341873.79066498, 341878.04533832,
            341882.30002303, 341886.55471912, 341890.80942658,
            341895.06414542, 341899.31887563, 341903.57361722,
            341907.82837019, 341912.08313453, 341916.33791024,
            341920.59269733, 341924.8474958 , 341929.10230564,
            341933.35712686, 341937.61195945, 341941.86680341,
            341946.12165876, 341950.37652547, 341954.63140356,
            341958.88629303, 341963.14119387, 341967.39610609,
            341971.65102968, 341975.90596465, 341980.16091099,
            341984.41586871, 341988.6708378 , 341992.92581827,
    ...
            342558.93956979, 342563.19607422, 342567.45259002,
            342571.70911719, 342575.96565573, 342580.22220565,
            342584.47876693, 342588.73533959, 342592.99192361,
            342597.24851901, 342601.50512578, 342605.76174392,
            342610.01837342, 342614.2750143 , 342618.53166655,
            342622.78833017, 342627.04500516, 342631.30169152,
            342635.55838926, 342639.81509836, 342644.07181883,
            342648.32855067, 342652.58529389, 342656.84204847,
            342661.09881442, 342665.35559175, 342669.61238044,
            342673.8691805 , 342678.12599194, 342682.38281474,
            342686.63964892, 342690.89649446, 342695.15335138,
            342699.41021966, 342703.66709931, 342707.92399034,
            342712.18089273, 342716.4378065 , 342720.69473163,
            342724.95166813, 342729.20861601, 342733.46557525,
            342744.01671286, 346362.97897869, 345859.93639209,
            345775.25735014, 346050.7958609 , 346071.2964588 ,
            346071.2964588 , 346071.2964588 , 346071.2964588 ,
            346071.2964588 , 346071.2964588 , 346071.2964588 ,
            346071.2964588 , 346071.2964588 , 346071.2964588 ,
            346071.2964588 , 346071.2964588 ]])
    Coordinates:
      * time        (time) datetime64[us] 2kB 2022-05-10T13:00:00 ... 2022-05-20T...
      * trajectory  (trajectory) <U18 72B 'dev864475040536665'
    Attributes:
        grid_mapping:  polar_stereographic




.. GENERATED FROM PYTHON SOURCE LINES 49-50

Extract the values of a variable for the trajectory

.. GENERATED FROM PYTHON SOURCE LINES 50-56

.. code-block:: Python

    temp = nk.isel(depth=0).sel(time=dst.time,
                                X=dst.x,
                                Y=dst.y,
                                method='nearest').temperature
    print(temp)





.. rst-class:: sphx-glr-script-out

 .. code-block:: none

    <xarray.DataArray 'temperature' (time: 251, trajectory: 1)> Size: 1kB
    [251 values with dtype=float32]
    Coordinates:
        X           (trajectory, time) float64 2kB 3.416e+05 3.416e+05 ... 3.464e+05
        Y           (trajectory, time) float64 2kB 4.344e+05 4.344e+05 ... 4.416e+05
        depth       float64 8B 0.0
      * time        (time) datetime64[ns] 2kB 2022-05-10T13:00:00 ... 2022-05-20T...
        lat         (trajectory, time) float64 2kB ...
        lon         (trajectory, time) float64 2kB ...
      * trajectory  (trajectory) <U18 72B 'dev864475040536665'
    Attributes:
        units:          Celsius
        time:           ocean_time
        grid:           grid
        location:       face
        field:          temperature, scalar, series
        grid_mapping:   projection_stere
        long_name:      Sea water potential temperature
        standard_name:  sea_water_potential_temperature
        _ChunkSizes:    [   1    1   17 2602]




.. GENERATED FROM PYTHON SOURCE LINES 57-58

Notice that the `lat` and `lon` variables from Norkyst match the original `lat` and `lon` from the dataset.

.. GENERATED FROM PYTHON SOURCE LINES 58-62

.. code-block:: Python


    plt.figure()
    temp.plot()
    plt.show()



.. image-sg:: /gallery/images/sphx_glr_example_model_along_trajectory_001.png
   :alt: depth = 0.0 [m], trajectory = dev864475040536665
   :srcset: /gallery/images/sphx_glr_example_model_along_trajectory_001.png
   :class: sphx-glr-single-img






.. rst-class:: sphx-glr-timing

   **Total running time of the script:** (1 minutes 6.526 seconds)


.. _sphx_glr_download_gallery_example_model_along_trajectory.py:

.. only:: html

  .. container:: sphx-glr-footer sphx-glr-footer-example

    .. container:: sphx-glr-download sphx-glr-download-jupyter

      :download:`Download Jupyter notebook: example_model_along_trajectory.ipynb <example_model_along_trajectory.ipynb>`

    .. container:: sphx-glr-download sphx-glr-download-python

      :download:`Download Python source code: example_model_along_trajectory.py <example_model_along_trajectory.py>`

    .. container:: sphx-glr-download sphx-glr-download-zip

      :download:`Download zipped: example_model_along_trajectory.zip <example_model_along_trajectory.zip>`


.. only:: html

 .. rst-class:: sphx-glr-signature

    `Gallery generated by Sphinx-Gallery <https://sphinx-gallery.github.io>`_