Source code for

Utilities for reading CSU-CHILL CHL files.


import struct
from datetime import datetime

import numpy as np

from ..config import FileMetadata, get_fillvalue
from ..core.radar import Radar
from .common import _test_arguments, make_time_unit_str, prepare_for_read

[docs]def read_chl( filename, field_names=None, additional_metadata=None, file_field_names=None, exclude_fields=None, include_fields=None, use_file_field_attributes=True, **kwargs ): """ Read a CSU-CHILL CHL file. Parameters ---------- filename : str Name of CHL file. field_names : dict, optional Dictionary mapping CHL field names to radar field names. If a data type found in the file does not appear in this dictionary or has a value of None it will not be placed in the radar.fields dictionary. A value of None, the default, will use the mapping defined in the Py-ART configuration file. additional_metadata : dict of dicts, optional Dictionary of dictionaries to retrieve metadata from during this read. This metadata is not used during any successive file reads unless explicitly included. A value of None, the default, will not introduct any addition metadata and the file specific or default metadata as specified by the Py-ART configuration file will be used. file_field_names : bool, optional True to use the CHL field names for the field names in the radar object. If this case the field_names parameter is ignored. The field dictionary will likely only have a 'data' key, unless the fields are defined in `additional_metadata`. exclude_fields : list or None, optional List of fields to exclude from the radar object. This is applied after the `file_field_names` and `field_names` parameters. include_fields : list or None, optional List of fields to include from the radar object. This is applied after the `field_file_names` and `field_names` parameters. Set to None to include all fields not in exclude_fields. use_file_field_attributes : bool, optional True to use information provided by in the file to set the field attribute `long_name`, `units`, `valid_max`, and `valid_min`. False will not set these unless they are defined in the configuration file or in `additional_metadata`. Returns ------- radar : Radar Radar object containing data from CHL file. """ # test for non empty kwargs _test_arguments(kwargs) # create metadata retrival object filemetadata = FileMetadata( "chl", field_names, additional_metadata, file_field_names, exclude_fields, include_fields, ) # read data chl_file = ChlFile(prepare_for_read(filename)) # time time = filemetadata("time") tdata = np.array(chl_file.time) min_time = np.floor(tdata.min()) time["data"] = (tdata - min_time).astype("float64") time["units"] = make_time_unit_str(datetime.utcfromtimestamp(min_time)) # range _range = filemetadata("range") _range["data"] = ( np.array(range(chl_file.ngates)) * chl_file.gate_spacing + chl_file.first_gate_offset ) _range["meters_between_gates"] = np.array(chl_file.gate_spacing) _range["meters_to_center_of_first_gate"] = 0.0 # scan_type scan_type = SCAN_MODE_NAMES[chl_file.scan_types[-1]] # fields fields = {} for i, fdata in chl_file.fields.items(): field_info = chl_file.field_info[i] field_name = filemetadata.get_field_name(field_info["name"]) if field_name is None: continue field_dic = filemetadata(field_name), get_fillvalue()) field_dic["data"] = fdata field_dic["_FillValue"] = get_fillvalue() if use_file_field_attributes: field_dic["long_name"] = field_info["descr"] field_dic["units"] = field_info["units"] field_dic["valid_max"] = field_info["max_val"] field_dic["valid_min"] = field_info["min_val"] fields[field_name] = field_dic # metadata metadata = filemetadata("metadata") metadata["instrument_name"] = chl_file.radar_info["radar_name"] metadata["original_container"] = "CHL" # longitude, latitude, altitude latitude = filemetadata("latitude") longitude = filemetadata("longitude") altitude = filemetadata("altitude") latitude["data"] = np.array([chl_file.radar_info["latitude"]], "f8") longitude["data"] = np.array([chl_file.radar_info["longitude"]], "f8") altitude["data"] = np.array([chl_file.radar_info["altitude"]], "f8") # sweep_number, sweep_mode, fixed_angle, sweep_start_ray_index, # sweep_end_ray_index sweep_number = filemetadata("sweep_number") sweep_mode = filemetadata("sweep_mode") fixed_angle = filemetadata("fixed_angle") sweep_start_ray_index = filemetadata("sweep_start_ray_index") sweep_end_ray_index = filemetadata("sweep_end_ray_index") sweep_number["data"] = np.arange(chl_file.num_sweeps, dtype="int32") sweep_mode["data"] = np.array( [SCAN_MODE_NAMES[i] for i in chl_file.scan_types], dtype="S" ) fixed_angle["data"] = np.array(chl_file.fixed_angle, dtype="float32") ray_count = chl_file.rays_per_sweep ssri = np.cumsum(np.append([0], ray_count[:-1])).astype("int32") sweep_start_ray_index["data"] = ssri sweep_end_ray_index["data"] = np.cumsum(ray_count).astype("int32") - 1 # azimuth, elevation azimuth = filemetadata("azimuth") elevation = filemetadata("elevation") azimuth["data"] = np.array(chl_file.azimuth, dtype="float32") elevation["data"] = np.array(chl_file.elevation, dtype="float32") # instrument parameters instrument_parameters = None chl_file.close() return Radar( time, _range, fields, metadata, scan_type, latitude, longitude, altitude, sweep_number, sweep_mode, fixed_angle, sweep_start_ray_index, sweep_end_ray_index, azimuth, elevation, instrument_parameters=instrument_parameters, )
class ChlFile: """ A file object for CHL data. Parameters ---------- filename : str or file-like. Name of CHL file to read or a file-like object pointing to the beginning of such a file. ns_time : bool True to determine ray collection times to the nano-second, False will only determine times to the second. debug : bool True to keep packet data in the _packets attribute to aid in debugging. Attributes ---------- ngates : int Number of gates per ray. num_sweeps : int Number of sweeps in the volume. gate_spacing : float Spacing in meters between gates. first_gate_offset : float Distance in meters to the first range gate. time : list of ints Time in seconds in epoch for each ray in the volume. azimuth : list of floats Azimuth angle for each ray in the volume in degrees. elevation : list of floats Elevation angle for each ray in the volume in degrees. fixed_angle : list of floats Fixed angles for each sweep. sweep_number : list of ints Sweep numbers reported in file. scan_types : list of ints Chill defined scan type for each sweep. rays_per_sweep : list of ints Number of rays in each sweep. fields : dict Dictionary of field data index by field number. radar_info : dict Radar information recorded in the file. field_info : dict Field information (limits, name, etc.) recorded in the file. processor_info : dict Processor information recorded in the file. """ def __init__(self, filename, ns_time=True, debug=False): # initalize attributes self.ngates = None self.num_sweeps = None self.gate_spacing = None self.time = [] self.azimuth = [] self.elevation = [] self.fixed_angle = [] self.sweep_number = [] self.scan_types = [] self.rays_per_sweep = None self.fields = {} self.radar_info = None self.field_info = {} self.processor_info = None self.first_gate_offset = None # private attributes self._dstring = b"" # string containing field data. self._bit_mask = None # bit mask specifying fields present in file. self._dtype = None # NumPy dtype for a single gate (all fields). self._ray_bsize = None # size in bytes of a single ray (all fields). self._packets = [] # List of packets, not set if debug is False. self._field_nums = None # Field number available in file. self._rays_in_current_sweep = None # accumulator for counting rays. self._fh = None # file handler self._include_ns_time = ns_time # read all blocks from the file if hasattr(filename, "read"): self._fh = filename else: self._fh = open(filename, "rb") packet = 1 while packet is not None: packet = self._read_block() if debug: self._packets.append(packet) self._extract_fields() self.rays_per_sweep.append(self._rays_in_current_sweep) def close(self): """Close the file.""" self._fh.close() def _read_block(self): """Read a block from an open CHL file.""" pld = if pld == b"": return None block_id, length = struct.unpack("<2i", pld) payload = - 8) # parse the block if block_id == ARCH_ID_FILE_HDR: packet = self._parse_file_hdr_block(payload) elif block_id == ARCH_ID_FIELD_SCALE: packet = self._parse_field_scale_block(payload) elif block_id == ARCH_ID_RAY_HDR: packet = self._parse_ray_hdr_block(payload) elif block_id == HSK_ID_RADAR_INFO: packet = self._parse_radar_info_block(payload) elif block_id == HSK_ID_PROCESSOR_INFO: packet = self._parse_processor_info_block(payload) elif block_id == HSK_ID_SCAN_SEG: packet = self._parse_scan_seg_block(payload) elif block_id == ARCH_ID_SWEEP_BLOCK: packet = self._parse_sweep_block(payload) else: packet = {} packet["block_id"] = block_id packet["length"] = length return packet # Block parsers def _parse_file_hdr_block(self, payload): """Parse a field_hdr block.""" return _unpack_structure(payload, ARCH_FILE_HDR_T) def _parse_field_scale_block(self, payload): """Parse a field_scale block. Add scale to field_info attr.""" packet = _unpack_structure(payload, FIELD_SCALE_T) packet["name"] = packet["name"].decode("utf-8").rstrip("\x00") packet["units"] = packet["units"].decode("utf-8").rstrip("\x00") packet["descr"] = packet["descr"].decode("utf-8").rstrip("\x00") self.field_info[packet["bit_mask_pos"]] = packet return packet def _parse_radar_info_block(self, payload): """Parse a radar_info block. Update metadata attribute.""" packet = _unpack_structure(payload, RADAR_INFO_T) packet["radar_name"] = packet["radar_name"].decode("utf-8").rstrip("\x00") self.radar_info = packet.copy() return packet def _parse_processor_info_block(self, payload): """Parse a processor_info block. Set dr attribute.""" packet = _unpack_structure(payload, PROCESSOR_INFO) self.gate_spacing = packet["gate_spacing"] self.first_gate_offset = packet["range_offset"] self.processor_info = packet.copy() return packet def _parse_scan_seg_block(self, payload): """Parse a scan_seg_block. Update sweep attributes.""" packet = _unpack_structure(payload, SCAN_SEG) self.sweep_number.append(packet["sweep_num"]) self.fixed_angle.append(packet["current_fixed_angle"]) self.scan_types.append(packet["scan_type"]) if self.rays_per_sweep is None: self.rays_per_sweep = [] # first sweep block self._rays_in_current_sweep = 0 else: self.rays_per_sweep.append(self._rays_in_current_sweep) self._rays_in_current_sweep = 0 return packet def _parse_sweep_block(self, payload): """Parse a sweep block. Set num_sweeps attribute.""" packet = {} packet["num_sweeps"] = struct.unpack("I", payload[0:4])[0] packet["swp_offsets"] = struct.unpack( str(packet["num_sweeps"]) + "Q", payload[4:] ) self.num_sweeps = packet["num_sweeps"] return packet def _parse_ray_hdr_block(self, payload): """Parse a ray_hdr block. Update associated attributes.""" packet = _unpack_structure(payload, ARCH_RAY_HEADER) if self._bit_mask is None: # this is the first ray_hdr block read self.ngates = packet["gates"] self._bit_mask = packet["bit_mask"] self._field_nums = [b for b in range(38) if self._bit_mask & 2**b] self._dtype = ",".join( [DATA_FORMAT[self.field_info[i]["format"]] for i in self._field_nums] ) self._ray_bsize = np.dtype(self._dtype).itemsize * packet["gates"] else: # check that the bit_mask and number of gates are constant if packet["bit_mask"] != self._bit_mask: raise NotImplementedError("bit_mask is not consistent.") if packet["gates"] != self.ngates: raise NotImplementedError("number of gates vary.") # store ray data and pointing data self._dstring += if self._include_ns_time: self.time.append(packet["time"] + packet["ns_time"] / 1e9) else: self.time.append(packet["time"]) self.azimuth.append(packet["azimuth"]) self.elevation.append(packet["elevation"]) self._rays_in_current_sweep += 1 return packet def _extract_fields(self): """Extract field data from _dstring attribute post read.""" all_data = np.frombuffer(self._dstring, dtype=self._dtype) all_data = all_data.reshape(-1, self.ngates) for i, field_num in enumerate(self._field_nums): fdata =[all_data.dtype.names[i]], 0) # apply scale and offset factors to interger data types if issubclass(fdata.dtype.type, np.integer): dat_factor = float(self.field_info[field_num]["dat_factor"]) dat_bias = float(self.field_info[field_num]["dat_bias"]) fld_factor = float(self.field_info[field_num]["fld_factor"]) fdata = (fdata * dat_factor + dat_bias) / fld_factor self.fields[field_num] = fdata return # CHL packet types ARCH_FORMAT_VERSION = 0x00010000 ARCH_ID_CONTROL = 0x5AA80001 ARCH_ID_FIELD_SCALE = 0x5AA80002 ARCH_ID_RAY_HDR = 0x5AA80003 ARCH_ID_FILE_HDR = 0x5AA80004 ARCH_ID_SWEEP_BLOCK = 0x5AA80005 HSK_ID_PROCESSOR_INFO = 0x5AA50003 HSK_ID_RADAR_INFO = 0x5AA50001 HSK_ID_SCAN_SEG = 0x5AA50002 # Additional constants SCAN_MODE_NAMES = ["ppi", "rhi", "fixed", "manual ppi", "manual rhi", "idle"] DATA_FORMAT = ["uint8", "uint64", "float32", "uint16"] ############## # Structures # ############## def _unpack_structure(string, structure): """Unpack a structure.""" fmt = "".join([i[1] for i in structure]) tpl = struct.unpack(fmt, string) return dict(zip([i[0] for i in structure], tpl)) ARCH_FILE_HDR_T = ( ("version", "I"), ("creation_version", "I"), ("creator_id", "32s"), ("sweep_table_offset", "Q"), ) ARCH_RAY_HEADER = ( ("azimuth", "f"), ("elevation", "f"), ("azimuth_width", "f"), ("elevation_width", "f"), ("gates", "H"), ("beam_index", "H"), ("ns_time", "I"), ("time", "Q"), ("bit_mask", "Q"), ("ray_number", "I"), ("num_pulses", "I"), ) FIELD_SCALE_T = ( ("format", "i"), ("min_val", "f"), ("max_val", "f"), ("bit_mask_pos", "i"), ("type_hint", "i"), ("fld_factor", "i"), ("dat_factor", "i"), ("dat_bias", "i"), ("name", "32s"), ("units", "32s"), ("descr", "128s"), ) RADAR_INFO_T = ( ("radar_name", "32s"), ("latitude", "f"), ("longitude", "f"), ("altitude", "f"), ("beamwidth", "f"), ("wavelength_cm", "f"), ("unused1", "f"), ("unused2", "f"), ("unused3", "f"), ("unused4", "f"), ("gain_ant_h", "f"), ("gain_ant_v", "f"), ("zdr_cal_base", "f"), ("phidp_rot", "f"), ("base_radar_constant", "f"), ("unused5", "f"), ("power_measurement_loss_h", "f"), ("power_measurement_loss_v", "f"), ("zdr_cal_base_vhs", "f"), ("test_power_h", "f"), ("test_power_v", "f"), ("dc_loss_h", "f"), ("dc_loss_v", "f"), ) PROCESSOR_INFO = ( ("polarization_mode", "i"), ("processing_mode", "i"), ("pulse_type", "i"), ("test_type", "i"), ("integration_cycle_pulses", "I"), ("clutter_filter_number", "I"), ("range_gate_averaging", "I"), ("indexed_beam_width", "f"), ("gate_spacing", "f"), ("prt_usec", "f"), ("range_start", "f"), ("range_stop", "f"), ("max_gate", "I"), ("test_power", "f"), ("unused1", "f"), ("unused2", "f"), ("test_pulse_range", "f"), ("test_pulse_length", "f"), ("prt2", "f"), ("range_offset", "f"), ) SCAN_SEG = ( ("az_manual", "f"), ("el_manual", "f"), ("az_start", "f"), ("el_start", "f"), ("scan_rate", "f"), ("segname", "24s"), ("opt", "i"), ("follow_mode", "i"), ("scan_type", "i"), ("scan_flags", "I"), ("volume_num", "I"), ("sweep_num", "I"), ("time_limit", "I"), ("webtilt", "I"), ("left_limit", "f"), ("right_limit", "f"), ("up_limit", "f"), ("down_limit", "f"), ("step", "f"), ("max_sweeps", "I"), ("filter_break_sweep", "I"), ("clutter_filter1", "I"), ("clutter_filter2", "I"), ("project", "16s"), ("current_fixed_angle", "f"), )