locate_signal.py

Go to the documentation of this file.

r"""!
@file  locate_signal.py
@brief `main()` shows how to use [cross_correlate()](#locate_signal.cross_correlate)
and [plot_correlation_map()](#locate_signal.plot_correlation_map).
 
\anchor example_one_pair_corr_map
![Unmasked and Masked Correlation Maps: one antenna pair](example_correlation_map_one_pair.png)
 
Summing over all antenna pairs, we have
 
\anchor example_corr_map
![Unmasked and Masked Total Correlation Maps](example_correlation_map_2D.png)
 
We can see that by masking the individual correlation maps, the total correlation map is less
noisy.
 
"""
 
import ROOT
import numpy as np
import polars as pl
import sys
from time_delays import _make_grid
from pathlib import Path
from initialise import load_pueoEvent_Dataset
 
 
 
 
def supply_azimuthal_angle_masks(skymaps: pl.DataFrame) -> pl.DataFrame:
    r"""!Supplies azimuth masks to any sky map
    (eg [time delay maps](#time_delays.make_time_delay_skymap) or
    [correlation maps](#cross_correlate))
    @ingroup CC
    @param[in]  skymaps        columns `A1_PhiSector` and `A2_PhiSector` are **required**
    @retval     phi_masks      see the schema of the example output below
 
* Parameters:
    *   Input: required columns are the \f$\phi\f$-sectors of the antenna pairs,
        `A1_PhiSector` and `A2_PhiSector`.
    *   Output schema: one column (`masks`) will be attached to the input dataframe,
```
$ A1_PhiSector                    <u8>
$ A2_PhiSector                    <u8>
$ masks        <array[bool, (1, 360)]>
```
 
* Explanation:
 
    * \f$\phi\f$-sector 1 is centered around 0 degrees azimuth, \f$\phi\f$-sector 2 around 15 degrees,
      and so on and so forth; the last \f$\phi\f$ sector (24) is centered around 345 degrees.
    * Based on the antenna's [field of view](#antenna_attributes.ASSUMED_PHI_SECTOR_APERTURE_WIDTH),
      the values outside a certain range are dropped.
    * In the figure below, we show what this would look like for antennas from the first three and
      the last \f$\phi\f$-sectors (white means masked).
 
      ![Example masks of a few phi-sectors](azimuthal_angle_masks_illustration.svg)
 
    * The chosen masking behavior for now is that **only the data within the overlapping unmasked
      range would be kept**.
    * For instance, suppose an antenna from \f$\phi\f$-sector 1 is paired with an antenna from
      \f$\phi\f$-sector 2, then:
 
      ![Example superimposed masks](azimuthal_angle_mask_overlap_illustration.svg)
 
    @warning
    * Thus, if the antenna pair's
      [fields of view](#antenna_attributes.ASSUMED_PHI_SECTOR_APERTURE_WIDTH)
      do not overlap, then everything will be masked.
    """
    from antenna_attributes import NUM_PHI_SECTORS, ASSUMED_PHI_SECTOR_APERTURE_WIDTH
    phi, _ = _make_grid(sparse=True)
    phi = np.degrees(phi)
 
    # eg. PhiSector 1 is centered around 0, so with aperture width 50 degrees,
    #     its bound would be (-25, 25)
    aperture_bounds = (
        pl.DataFrame(
            {"PhiSector": np.arange(1, 25)}, schema={"PhiSector": pl.UInt8}
        )
        .with_columns
        (
            ((pl.col("PhiSector") - 1) * (360 / NUM_PHI_SECTORS)).alias("aperture center [deg]")
        )
        .with_columns
        (
            pl.col("aperture center [deg]"),
            (
                (pl.col("aperture center [deg]") - ASSUMED_PHI_SECTOR_APERTURE_WIDTH / 2)
            ).alias("left bound [deg]"),
            (
                (pl.col("aperture center [deg]") + ASSUMED_PHI_SECTOR_APERTURE_WIDTH / 2)
            ).alias("right bound [deg]"),
        )
    )
 
    phi_masks = (
        skymaps
        .join(
            aperture_bounds.select(
                pl.col("PhiSector"),
                pl.col("left bound [deg]").alias("A1 left"),
                pl.col("right bound [deg]").alias("A1 right"),
            ), left_on="A1_PhiSector", right_on="PhiSector"
        ).join(
            aperture_bounds.select(
                pl.col("PhiSector"),
                pl.col("left bound [deg]").alias("A2 left"),
                pl.col("right bound [deg]").alias("A2 right"),
            ), left_on="A2_PhiSector", right_on="PhiSector"
        ).with_columns(
            pl.struct(pl.col("A1 left"), pl.col("A1 right"))
            .map_batches
            (
                lambda s: np.array([
                    ((phi - left) % 360) < ((right - left) % 360)
                    for left, right
                    in s.to_numpy()
                ])
            ).alias("A1 masks"),
            pl.struct(pl.col("A2 left"), pl.col("A2 right"))
            .map_batches
            (
                lambda s: np.array([
                    ((phi - left) % 360) < ((right - left) % 360)
                    for left, right
                    in s.to_numpy()
                ])
            ).alias("A2 masks")
        )
        .select(
            pl.all().exclude(
                "A1 masks", "A2 masks", "A1 left", "A2 left", "A1 right", "A2 right"
            ),
            pl.struct("A1 masks", "A2 masks").map_batches(
                lambda s: np.array([  # note: only overlapping part is kept, hence the element-wise &
                    ~(m1 & m2) for m1, m2 in s.to_numpy()
                ])  # the not (~) is used since True means masked in NumPy.
            ).alias("masks")
        )
    )
    return phi_masks
 
 
def combine_time_delay_maps_and_waveforms(masks_and_skymaps: pl.DataFrame,
                                          waveforms: pl.DataFrame) -> pl.DataFrame:
    r"""!Prepares a big table that has all the column needed by #cross_correlate.
    @ingroup CC
    @param[in]  masks_and_skymaps  The output of #supply_azimuthal_angle_masks
    @param[in]  waveforms          The output of #waveform_plots.load_waveforms
    @retval     big_frame          See sample output schema below.
 
    * Parameters:
        *   The following columns are required in `waveforms`:
            -#  `AntNum`
            -#  `waveforms (volts)`
            -#  `step size (nanoseconds)`
            -#  `Pol`
        *   The following columns are required in `masks_and_skymaps`:
            -#  `A1_AntNum`
            -#  `A2_AntNum`
            -#  `time delays [sec]`
            -#  `masks`
        *   The output schema:
```
$ A1_AntNum                               <enum>
$ A2_AntNum                               <enum>
$ Pol                                     <enum>
$ A1_waveforms (volts)        <array[f64, 3072]>
$ A2_waveforms (volts)        <array[f64, 3072]>
$ time delays [samples] <array[i64, (180, 360)]>
$ masks                  <array[bool, (1, 360)]>
```
    * Explanation:
        * `time delays [samples]` refers to the [time delay skymaps](#time_delays.make_time_delay_skymap),
          with the units converted from seconds to "samples"
        * That is, the units are in "steps" (`step size (nanoseconds)`)
        * The values in these time delay skymaps are therefore integers, serving as indices.
        * These indices are then used later in #cross_correlate when creating the
          correlation skymaps based on the time delay maps (via "fancy-indexing").
        * Qualitatively, the time delay maps have not changed. For example:
          \image html time_delay_map_in_seconds.svg  Time Delay Map in Seconds  width=40%
          \image html time_delay_map_in_samples.svg  Time Delay Map in Samples  width=40%
    """
 
    signal_length = len(waveforms["waveforms (volts)"][0])
    step_size = waveforms["step size (nanoseconds)"][0] * 1e-9  # ns -> seconds
 
    big_frame = (
        masks_and_skymaps
        .join(waveforms, left_on="A1_AntNum", right_on="AntNum")
        .join(waveforms, left_on=["A2_AntNum", "Pol"], right_on=["AntNum", "Pol"])
        .with_columns(
            (  # Convert [sec] to [number of samples]
                pl.col("time delays [sec]") / step_size + signal_length - 1
               # This offset is related to scipy.signal.correlate's behavior.
            )  # Next, round the time delay maps to integers.
            .map_batches(lambda s: np.rint(s.to_numpy()).astype(int))
            .alias("time delays [samples]")
        )
        .with_columns(
            pl.col("waveforms (volts)").alias("A1_waveforms (volts)"),
            pl.col("waveforms (volts)_right").alias("A2_waveforms (volts)")
        )
        .select(
            r"^A[12]_AntNum$", "Pol", r"^A[12]_waveforms \‍(volts\‍)$", "time delays [samples]", "masks"
        )
    )
 
    return big_frame
 
 
def cross_correlate(big_frame: pl.DataFrame) -> pl.DataFrame:
    r"""!Compute the zero-centered normalized cross correlation (ZNCC) and makes correlation skymaps
    @ingroup CC
    @param[in]  big_frame        The output of #combine_time_delay_maps_and_waveforms()
    @retval     correlation_maps See the schema of the example output below
 
    *   Parameters: columns `correlation` and `correlation maps` will be added to the input,
        so the output schema looks like
```
$ A1_AntNum                               <enum>
$ A2_AntNum                               <enum>
$ Pol                                     <enum>
$ A1_waveforms (volts)        <array[f64, 3072]>
$ A2_waveforms (volts)        <array[f64, 3072]>
$ time delays [samples] <array[i64, (180, 360)]>
$ masks                  <array[bool, (1, 360)]>
$ correlation                 <array[f64, 6143]>
$ correlation maps      <array[f64, (180, 360)]>
```
        *   `correlation maps` contain correlation skymaps.
            These are matrices with the same dimensions as the time delay maps of `time delays [samples]`,
            as the former are made based on the latter via "fancy-indexing"
 
        *   Each matrix element of a correlation skymap is the correlation score between two waveforms,
            given some particular [time delay](#time_delays.make_time_delay_skymap), ie. phase shift.
            \anchor effectOfMask
            ![Unmasked and Masked Correlation Maps](example_correlation_map_one_pair.png)
 
        * `masks` can be used to mask the correlation maps, as shown in the bottom subplot in the
          Figure above. The masks are defined by #supply_azimuthal_angle_masks.
 
        \anchor scipy_corr_expl
    *   Explanation:
        *   Consider two waveforms,
            \anchor maxcorrachieved
            \image html shift_by_472_samples.png
        *   Each row in the `correlation` column is an array of correlation scores.
        *   By shifting the waveforms we may be able to get them to align perfectly,
            at which point maximum correlation is achieved.
        *   The correlation score tells us how "aligned" the two waveforms are after we phase shift
            `A1_waveforms (volts)` against `A2_waveforms (volts)` by a certain amount of time.
        *   The waveforms are zero-centered and normalized such that the cross-correlation is
            bounded between [-1,1]. Zero means the waveforms are not aligned at all.
        *   See [cross_correlation_and_time_delay.pdf](cross_correlation_and_time_delay.pdf) or,
            for details, [scipy_correlate_behavior.pdf](scipy_correlate_behavior.pdf).
 
    """
    from scipy.signal import correlate
 
    correlation_maps: pl.DataFrame = (
        big_frame
        .with_columns
        (
            pl.struct("A1_waveforms (volts)", "A2_waveforms (volts)")
            .map_batches                # pass the waveform pair to a lambda function
            (                           # the lambda function runs scipy's correlate
                lambda s: np.array([
                    correlate(  # compute the zero-center normalized cross-correlation (ZNCC)
                        (wf1 - np.mean(wf1)) / np.std(wf1),  # so that CC is bounded b/w [-1, 1]
                        (wf2 - np.mean(wf2)) / np.std(wf2),  # zero-center and normalize the signals
                        method='fft'
                    ) / len(wf1)
                    for wf1, wf2 in s.to_numpy()
                ])
            )
            .alias("correlation"),
        )
        .with_columns  # make correlation maps via "fancy-indexing" inside the lambda function
        (
            pl.struct(pl.col("time delays [samples]"), pl.col("correlation")).map_batches(
                lambda s: np.array(
                    [correlation_array[time_delay_matrix]
                     for time_delay_matrix, correlation_array
                     in s.to_numpy()]
                )
            ).alias("correlation maps")
        )
    )
 
    return correlation_maps
 
 
def _get_true_direction(dataset: ROOT.pueo.Dataset) -> [float, float]:
    r"""!
    @brief Returns the true signal direction in MC
    @ingroup CC
    @param[in] dataset       The output of #initialise.load_pueoEvent_Dataset
 
    * Note that as stored in the `.root` files,
      the variable `RFdir_payload` is the direction the signal is travelling **to**.
    * Therefore, to obtain the direction that the signal is coming **from**,
      we need the opposite vector.
    * Thus, \f$\phi_{\rm true} = (\phi_{\rm rfdir} + 180 ^\circ) \% 360^\circ\f$,
      and \f$\theta_{\rm true} = 180^\circ - \theta_{\rm rfdir}\f$
    """
 
    truePhi = (dataset.truth().payloadPhi + 180) % 360
    trueTheta = 180 - dataset.truth().payloadTheta
    #print("truePhi, trueTheta=", truePhi, trueTheta)
    return truePhi, trueTheta
 
def _get_true_pulser_direction_tmp(dataset: ROOT.pueo.Dataset, pulser_station:str, nav_file = "../abxtwo.root") -> [float, float]:
    r"""!
    @brief Temperary before payload gps data is attached to each event. Returns the true signal direction in payload coor. 
    @ingroup CC
    @param[in] dataset       The output of #initialise.load_pueoEvent_Dataset
    @param[in] pulser_station name of the pulser station, ldb, taylor_dome, s200
    @retval    phi, theta in payload coor.
 
    * Note that as stored in the `.root` files,
      the variable `RFdir_payload` is the direction the signal is travelling **to**.
    * Therefore, to obtain the direction that the signal is coming **from**,
      we need the opposite vector.
    * Thus, \f$\phi_{\rm true} = (\phi_{\rm rfdir} + 180 ^\circ) \% 360^\circ\f$,
      and \f$\theta_{\rm true} = 180^\circ - \theta_{\rm rfdir}\f$
    """
    sys.path.append("/home/yuchiehku/pueo/pueoBuilder/components/pueoAnalysisTools")
    import geographyUtils.locations
    import geographyUtils.navigation
    import geographyUtils.geometry
    
    readout_time = dataset.header().readoutTime    
    
    locations_helper = geographyUtils.locations.LocationsHelper()
    navigation_helper = geographyUtils.navigation.NavigationHelper(root_file=nav_file, root_source="ABX-Two")
    geometry_helper = geographyUtils.geometry.GeometryHelper()
 
    if len(pulser_station) > 0:
        pulser_position = locations_helper.get_ground_pulser_position(pulser_station)
        pueo_position = np.zeros(3)
        pueo_position[0] = navigation_helper.get_longitude(readout_time, max_time_delta=1)
        pueo_position[1] = navigation_helper.get_latitude(readout_time, max_time_delta=1)
        pueo_position[2] = navigation_helper.get_altitude(readout_time, max_time_delta=1)
        pueo_heading = navigation_helper.get_heading(readout_time, max_time_delta=1) + 45.3 # If abx2 is used, there is a 45.3 deg offset between abx2 and the payload coor.
        expected_el_az = geometry_helper.get_direction_of_position(
            pulser_position,
            pueo_position
            )
        # correct for different direction definitions
        expected_signal_direction = np.zeros(2)
        expected_signal_direction[0] = expected_el_az[0] # this is payload elevation
        expected_signal_direction[1] = 1*(-expected_el_az[1] + pueo_heading) #someone should check this!
        while expected_signal_direction[1] < 0:
            expected_signal_direction[1] += 360
        while expected_signal_direction[1] > 360:
            expected_signal_direction[1] -= 360
    else:
        expected_signal_direction = None
 
    return expected_signal_direction[1], -1*expected_signal_direction[0]+90 # phi, theta, -1*theta+90 to convert from payload elevation to zenith angle
 
def _get_true_pulser_direction(dataset: ROOT.pueo.Dataset, pulser_station:str) -> [float, float]:
    r"""!
    @brief Returns the true signal direction from pulser and payload location
    @ingroup CC
    @param[in] dataset       The output of #initialise.load_pueoEvent_Dataset
    @param[in] pulser_station name of the pulser station, ldb, taylor_dome, s200
    @retval    phi, theta in payload coor.     
 
    * Does this function work on the data format? probably not now, but eventually it will
    * Note that as stored in the `.root` files,
      the variable `RFdir_payload` is the direction the signal is travelling **to**.
    * Therefore, to obtain the direction that the signal is coming **from**,
      we need the opposite vector.
    * Thus, \f$\phi_{\rm true} = (\phi_{\rm rfdir} + 180 ^\circ) \% 360^\circ\f$,
      and \f$\theta_{\rm true} = 180^\circ - \theta_{\rm rfdir}\f$
    """
 
    sys.path.append(str(Path(__file__).resolve().parent.parent))
    import geographyUtils.locations
    import geographyUtils.geometry
 
    geometry_helper = geographyUtils.geometry.GeometryHelper()
    locations_helper = geographyUtils.locations.LocationsHelper()
 
    pulser_position = locations_helper.get_ground_pulser_position(pulser_station)
    
    pueo_position = np.zeros(3)
    # Eventually we will use this, but now it's not supported by the data format
    '''
    pueo_position[0] = dataset.gps().longitude
    pueo_position[1] = dataset.gps().latitude
    pueo_position[2] = dataset.gps().altitude
    
    pueo_heading = dataset.gps().heading
    '''
    pueo_position[0] = 0
    pueo_position[1] = 0
    pueo_position[2] = 0
 
    pueo_heading = 0
    expected_el_az = geometry_helper.get_direction_of_position(
        pulser_position,
        pueo_position
        )
    # correct for different direction definitions # check if this match the difinition used in calibration.py
    expected_signal_direction = np.zeros(2)
    
    # zenith
    expected_signal_direction[0] = 180 - expected_el_az[0] 
    
    #azimuth
    expected_signal_direction[1] = (-expected_el_az[1] + 180 + pueo_heading)
    
    while expected_signal_direction[1] < 0:
        expected_signal_direction[1] += 360
    while expected_signal_direction[1] > 360:
        expected_signal_direction[1] -= 360
    
    truePhi = expected_signal_direction[1]
    trueTheta = expected_signal_direction[0]
 
    return truePhi, trueTheta
 
def plot_correlation_map(correlation_frame: pl.DataFrame, plot_name: str,
                         true_phi=None, true_theta=None) -> None:
    r"""!
    @brief Plots the reult of #cross_correlate.
    @ingroup CC
    @param[in]  correlation_frame  The output of #cross_correlate
    @param[in]  plot_name          Remember to specify file type
    @param[in]  true_phi           (optional) from #_get_true_direction
    @param[in]  true_theta         (optional) from #_get_true_direction
 
    *   Required columns in `correlation_frame`:
        -#  `correlation maps`
        -#  `masks`
        -#  `Pol`
 
    *   Using only one antenna pair, one can find a band of peak correlation scores,
        see the [plot in the file description](@ref example_one_pair_corr_map).
 
    *   If we then sum over all antenna pairs, we would be able to identify a single peak:
 
    ![Correlation Skymaps (summed over all antenna pairs)](img/example_correlation_map_two_pols.png)
 
    """
    import matplotlib.pyplot as plt
    import numpy.ma as ma
    plt.rcParams.update({'font.size': 15})
 
    phi, theta = _make_grid(sparse=True)
    phi = np.degrees(phi)
    theta = np.degrees(theta)
 
    fig, axes = plt.subplots(2, 1, figsize=(20, 10), sharex=True)
    for i, df in enumerate(correlation_frame.partition_by("Pol")):
        corr_map = df["correlation maps"].to_numpy()
        # repeat each mask (row vector) 300 times (ie. the dimension of theta),
        # so that each mask (now a matrix) has the same dimension as the corresponding correlation map
        masks = np.repeat(df["masks"].to_numpy(), repeats=np.shape(corr_map)[1], axis=1)
        masks_sum = np.sum(~masks, axis=0)  # for normalizing `total_masked`
        # Since True means masked in numpy's masked array, a `not` (~) is needed in the sum above.
        corr_map_masked = ma.array(corr_map, mask=masks)
 
        # sum the correlation maps
        total_masked = np.sum(corr_map_masked, axis=0) / masks_sum
 
        axes[i].set_ylabel(r"$\theta$")
        axes[i].set_xlabel(r"$\phi$")
        axes[i].set_title(f"{df['Pol'][0]}Pol correlation maps")
        fig.colorbar(axes[i].pcolormesh(phi, theta, total_masked))
 
        if true_phi is not None and true_theta is not None:
            axes[i].scatter(true_phi, true_theta, marker='x', color="red", label='True Direction')
            axes[i].legend()
 
    fig.savefig(plot_name)
 
 
# note: internal function for creating an example plot used by the documentation; not documented.
def __plot_example_correlation_map_for_one_antenna_pair(input_frame: pl.DataFrame):
    import matplotlib.pyplot as plt
    import numpy.ma as ma
    plt.rcParams.update({'font.size': 15})
 
    pl.Config().set_tbl_cols(input_frame.width)
    pl.Config().set_fmt_table_cell_list_len(0)
    print(input_frame)
 
    # retrieve the correlation map from the dataframe, and its corresponding mask
    mask = input_frame["masks"].to_numpy().squeeze()
    corr_map = input_frame["correlation maps"].to_numpy().squeeze()
 
    # applying mask to the correlation map
    mask = np.vstack([mask] * corr_map.shape[0])
    corr_map_masked = ma.array(corr_map, mask=mask)
 
    # plots
    phi, theta = _make_grid(sparse=True)
 
    fig, axes = plt.subplots(2, 1, sharex=True, figsize=(20, 10))
    axes[0].set_title(
        f"Antennas {input_frame['A1_AntNum'][0]} and {input_frame['A2_AntNum'][0]} Correlation Map"
    )
    for ax in axes:
        ax.set_ylabel(r"$\theta$")
        ax.set_yticks([np.pi / 2, np.pi], labels=[r"$\pi / 2$", r"$\pi$"])
 
    axes[1].set_xlabel(r"$\phi$")
    axes[1].set_xticks([0, np.pi, 2 * np.pi], labels=["0", r"$\pi$", r"$2\pi$"])
    image = axes[0].pcolormesh(phi, theta, corr_map, vmin=corr_map.min(), vmax=corr_map.max())
    image = axes[1].pcolormesh(phi, theta, corr_map_masked, vmin=corr_map.min(), vmax=corr_map.max())
    fig.colorbar(image, ax=axes.ravel().tolist(), label="Correlation Score")
    plt.savefig("img/example_correlation_map_one_pair.png")
 
 
if __name__ == "__main__":
    import os
    from antenna_attributes import read_antenna_geometry, get_nominal_phase_center
    from antenna_pairs import generate_MI_antenna_pairs
    from time_delays import make_time_delay_skymap
    from waveform_plots import load_waveforms, upsample_waveforms
 
    #  ----------------------- step 1: read in antenna geometry -----------------------  #
 
    _jun25: Path = os.environ.get("PUEO_UTIL_INSTALL_DIR") / Path("share/pueo/geometry/jun25/qrh.dat")
    _face_centers: pl.DataFrame = read_antenna_geometry(qrh_dot_dat=_jun25)
    # keep only the necessary columns for the task at hand
    _phase_centers: pl.DataFrame = (
        get_nominal_phase_center(face_centers=_face_centers)
        .select("AntNum", "PhiSector", "AntIdx", "X[m]", "Y[m]", "Z[m]")
    )
 
    #  ------------------- step 2: pair up antennas and compute the time delays -------------------  #
 
    _antenna_pairs: pl.DataFrame = generate_MI_antenna_pairs(antennas=_phase_centers)
    _time_delays: pl.DataFrame = (
        make_time_delay_skymap(antenna_pairs=_antenna_pairs)
        .select(pl.col(r"^A[12]_AntNum$", r"^A[12]_PhiSector$", "time delays [sec]"))
    )
 
    #  ----------------------- step 3: supply phi masks -----------------------  #
 
    masked: pl.DataFrame = (
        supply_azimuthal_angle_masks(skymaps=_time_delays)
        .select(pl.col(r"^A[12]_AntNum$", "time delays [sec]", "masks"))
    )
 
    #  ----------------------- step 4: get the waveforms -----------------------  #
 
    _run_zero_data: ROOT.pueo.Dataset = load_pueoEvent_Dataset(pueo_mc_data=Path("/tmp"), run_number=0)
    _run_zero_data.last()  # suppose we want to analyze the last event in run0/
 
    _wf: pl.DataFrame = (
        load_waveforms(dataset=_run_zero_data)
        .select("AntNum", "Pol", "waveforms (volts)", "step size (nanoseconds)")
    )
    up: pl.DataFrame = upsample_waveforms(waveforms=_wf, upsample_factor=3)
 
    #  ----------------------- step 5: apply cross correlation -----------------------  #
 
    big_frame = combine_time_delay_maps_and_waveforms(masks_and_skymaps=masked, waveforms=up)
 
    correlation_frame: pl.DataFrame = cross_correlate(big_frame)
 
    #  ----------------------- step 6: plots -----------------------  #
 
    tp, tt = _get_true_direction(dataset=_run_zero_data)
    plot_correlation_map(
        correlation_frame=correlation_frame, true_phi=tp, true_theta=tt,
        plot_name='img/example_correlation_map_two_pols.png'
    )
 
    # make the correlation map for one pair of antennas for the example plot in the documentation
    # __plot_example_correlation_map_for_one_antenna_pair(
    #     correlation_frame
    #     .filter(
    #         (pl.col("A1_AntNum") == "319"), pl.col("A2_AntNum") == "221", pl.col("Pol") == "V"
    #     )
    # )