LEMI-423 Binary Data Processor

Overview

This repository contains scripts for processing LEMI-423 broadband magnetotelluric 'Level 0' binary data.
It extracts metadata from binary file headers, reads time-series data, and organizes results into structured dataframes.
Supports parallel processing.

Features

• Reads and extracts metadata from LEMI-423 binary files.
• Processes time-series data with calibration coefficients.
• Logs operations for debugging and monitoring.

Requirements

• Python 3.x

Usage

Run the Processor

python Process_LEMI_423.py <path_to_metadata_csv> [num_cpus]

*.B423 Binary File Format

LEMI *.B423 binary files consist of:

1. 1024-byte ASCII header (contains Instrument number, firmware Ver, Date Time, Lat, Lon, Alt, scaling coefficients)
2. Raw measurement data as:

Field	Description
SECOND_TIMESTAMP	UTC timestamp (long)
SAMPLE_NUM	Sample number (0 - FS) (short)
Bx	Channel 1 (long)
By	Channel 2 (long)
Bz	Channel 3 (long)
Ex	Channel 4 (long)
Ey	Channel 5 (long)
PPS	Deviation from PPS (short)
PLL	PLL accuracy (short)

The raw data for the above channels (Bx, By, Bz, Ex, Ey) are in integer counts.

However, additional scalings (coefficients from the header) from the *.B423 files are applied to give:

• millivolts (mV) for the magnetic channels
• microvolts (uV) for the electric channels

The scalings are:

• Channel 1 = (Channel 1 * Kmx) + Ax
• Channel 2 = (Channel 1 * Kmy) + Ay
• Channel 3 = (Channel 1 * Kmz) + Az
• Channel 4 = (Channel 1 * Ke1) + Ae1
• Channel 5 = (Channel 1 * Ke2) + Ae2

Additional scaling to pyhsical units, will also have to be applied.

• Convert electrical data to mV/km
  • By dividing Ex and Ey by the dipole distance (m)
• Convert magnetic data to nT
  • Magnetic coils need calibrating from the *.RSP file
  • That have the following units:
    • Freq (Hz)
    • Magnitude (mV/nT)
    • Phase (deg)
  • Converted to the following units:
    • Freq (Hz)
    • Magnitude (mV/nT)
    • Phase (radians)