MoTeC LD File Reader

A Node.js library for reading MoTeC .ld telemetry files. This library allows you to parse and extract data from MoTeC data logging files commonly used in motorsports and automotive testing.

Features

• Parse MoTeC .ld files
• Access session metadata (driver, vehicle, venue, datetime, etc.)
• Read channel data (speed, RPM, temperature, etc.)
• Support for multiple data types (int16, int32, float16, float32)
• TypeScript support with full type definitions
• Lazy loading of channel data for efficient memory usage

Installation

npm install
npm run build

Usage

Basic Example

import { LdData } from 'motec-ld-reader';

// Read an .ld file
const data = LdData.fromFile('path/to/file.ld');

// Access metadata
console.log(`Driver: ${data.head.driver}`);
console.log(`Vehicle: ${data.head.vehicleId}`);
console.log(`Date: ${data.head.datetime}`);
console.log(`Venue: ${data.head.venue}`);

// List all channels
console.log('\nAvailable channels:');
data.getChannelNames().forEach(name => {
  console.log(`  - ${name}`);
});

// Access a specific channel by name
const speedChannel = data.getChannel('Ground Speed');
console.log(`\nSpeed channel:`);
console.log(`  Name: ${speedChannel.name}`);
console.log(`  Unit: ${speedChannel.unit}`);
console.log(`  Frequency: ${speedChannel.freq} Hz`);
console.log(`  Data points: ${speedChannel.data.length}`);

// Access channel data
const speeds = speedChannel.data;
console.log(`  Max speed: ${Math.max(...speeds)} ${speedChannel.unit}`);
console.log(`  Avg speed: ${speeds.reduce((a, b) => a + b, 0) / speeds.length} ${speedChannel.unit}`);

Access Channels by Index

// Access channels by numeric index
const firstChannel = data.getChannel(0);
console.log(firstChannel.name);

// Iterate over all channels
for (let i = 0; i < data.channelCount; i++) {
  const channel = data.getChannel(i);
  console.log(`${i}: ${channel.name} (${channel.unit})`);
}

Export to JSON

// Convert to a plain object for JSON serialization
const dataObject = data.toObject();
console.log(JSON.stringify(dataObject, null, 2));

// Or just get the data as a map
const dataMap = data.toDataMap();
console.log(dataMap['Ground Speed']);

Working with Channel Data

// Get multiple channels
const rpm = data.getChannel('Engine RPM').data;
const throttle = data.getChannel('Throttle Pos').data;
const speed = data.getChannel('Ground Speed').data;

// Perform calculations
for (let i = 0; i < Math.min(rpm.length, throttle.length); i++) {
  if (throttle[i] > 80) {
    console.log(`Full throttle at ${i}s: ${speed[i]} km/h, ${rpm[i]} RPM`);
  }
}

Channel Information

Each channel provides the following properties:

• name: Full channel name
• shortName: Abbreviated name
• unit: Unit of measurement
• freq: Sample frequency in Hz
• data: Array of data values (lazy loaded)
• dataLen: Number of data points

Metadata Access

// Event information
if (data.head.event) {
  console.log(`Event: ${data.head.event.name}`);
  console.log(`Session: ${data.head.event.session}`);
  console.log(`Comment: ${data.head.event.comment}`);

  // Venue information
  if (data.head.event.venue) {
    console.log(`Venue: ${data.head.event.venue.name}`);

    // Vehicle information
    if (data.head.event.venue.vehicle) {
      const vehicle = data.head.event.venue.vehicle;
      console.log(`Vehicle ID: ${vehicle.id}`);
      console.log(`Vehicle Type: ${vehicle.type}`);
      console.log(`Weight: ${vehicle.weight}`);
    }
  }
}

API Reference

LdData

Main class for reading .ld files.

Methods

• static fromFile(filePath: string): LdData - Read and parse an .ld file
• getChannel(nameOrIndex: string | number): LdChan - Get a channel by name or index
• getChannelNames(): string[] - Get all channel names
• toObject() - Convert to plain object for serialization
• toDataMap(): Record<string, number[]> - Get channel data as name-to-data map

Properties

• head: LdHead - Header/metadata information
• channels: LdChan[] - Array of all channels
• channelCount: number - Number of channels

LdHead

Header information containing metadata about the recording session.

Properties

• driver: string
• vehicleId: string
• venue: string
• datetime: Date
• shortComment: string
• event: LdEvent | null

LdChan

Channel data and metadata.

Properties

• name: string - Full channel name
• shortName: string - Abbreviated name
• unit: string - Unit of measurement
• freq: number - Sample frequency in Hz
• data: number[] - Data array (lazy loaded)
• dataLen: number - Number of data points
• dtype: DataType - Data type ('int16' | 'int32' | 'float16' | 'float32')

File Format

The .ld file format is a binary format used by MoTeC data loggers. The library handles:

• File header with session metadata
• Event, venue, and vehicle information
• Channel metadata (linked list structure)
• Binary channel data with various numeric types
• Data scaling and conversion formulas

Development

# Install dependencies
npm install

# Build the project
npm run build

# Watch mode for development
npm run watch

License

MIT

Credits

This library was created through reverse engineering the MoTeC .ld file format. It is not officially affiliated with MoTeC.