File format reference - A121

This page explains the format of A121 data files saved from Exploration Tool using the application or recorders in the API. A121 records are currently only stored in HDF5 (.h5).

Tip

We recommend loading and saving records using the built in functions in the acconeer.exptool.a121 module.

See examples/a121/load_record.py for an example of loading data, and examples/a121/record_data/barebones.py for saving data. For an example of how to load HDF5 records in Matlab, see examples/a121/load_record_h5.m.

Examples of loading

Some minimal examples of loading the session config from a data file:

Using acconeer.exptool.a121.load_record() (recommended):

from acconeer.exptool import a121
record = a121.load_record("data.h5")
print(record.session_config)
# SessionConfig:
#   extended ............... False
#   ...

Using h5py:

import json
import h5py
with h5py.File("data.h5") as f:
   print(json.loads(f["session/session_config"][()]))
# {'groups': [{'1': {'sweep_rate': None,
#     'frame_rate': None,
#     ...

HDF5 structure

client_info

JSON string representation of ClientInfo.

generation

String containing the sensor generation, i.e., “a121”.

lib_version

String containing the Exploration Tool version used to record.

server_info

JSON string representation of ServerInfo.

session

A soft link to sessions/session_0. Used for backwards-compatibility.

sessions/session_X

HDF5 group containing all data related to the recorded session. X is an integer starting from 0.

group_Y/entry_Z/

HDF5 group for entry Z in configuration group Y. Y and Z are integers starting from 0.

result/

HDF5 group with a dataset for every field in the Result.

Results are “stacked” into StackedResults to form the datasets. For example, the boolean scalar (single value) data_saturated becomes a 1D boolean array. In a Record, these can be accessed via stacked_results.

frame

3D array with dimensions (frame, sweep, distance) of the original complex data from the session.

The data type is a structured type with fields real and imag, both 16 bit signed integers (int16).

Note

Not the same type as frame.

data_saturated

1D boolean array with dimension (frame) of the data_saturated flags.

...

See fields in Result.

metadata

JSON string representation of Metadata.

sensor_id

Integer representing the sensor ID.

Note

Within a group, the sensor ID is unique for every entry.

session_config

JSON string representation of SessionConfig.

timestamp

String containing an ISO 8601 formatted timestamp at the time of creating the H5Recorder.

uuid

String containing a randomly generated version 4 UUID.