# 4.6.1.2.4. eqcorrscan.core.bright_lights._read_tt

`eqcorrscan.core.bright_lights.``_read_tt`(path, stations, phase, phaseout='S', ps_ratio=1.68, lags_switch=True)

  Read in .csv files of slowness generated from Grid2Time.

  Converts these data to a useful format here.

  It should be noted that this can read either P or S travel-time grids, not both at the moment.

  Parameters: | path (str) The path to the .csv Grid2Time outputs stations (list) List of station names to read slowness files for. phase (str) Input phase type. phaseout (str) What phase to return the lagtimes in. ps_ratio (float) p to s ratio for conversion lags_switch (bool) Return lags or raw travel-times, if set to true will return lags.
  Returns: | Stations
  Return type: | list
  Returns: | List of lists of tuples of node locations
  Return type: | list
  Returns: | Array of lags.
  Return type: | `numpy.ndarray`

  Note

  Output:

  station[1] refers to nodes[1] and lags[1] nodes[1][1] refers to station[1] and lags[1][1] nodes[n][n] is a tuple of latitude, longitude and depth.

  Note

  This function currently needs comma separated grid files in NonLinLoc format. Only certain versions of NonLinLoc write these csv files, however it should be possible to read the binary files directly. If you find you need this capability let us know and we can try and implement it.