GpsSimul

GpsSimul User Guide: Master GPS Signal Simulation GPS simulation is a critical requirement for testing navigation algorithms, autonomous vehicles, and location-aware applications. GpsSimul is a powerful, lightweight command-line tool designed to generate custom GPS baseband signal data. This guide will walk you through setting up, configuring, and executing your first GPS signal simulation. 🛠️ System Prerequisites and Setup

Before generating signal files, you must prepare your environment and install the core dependencies. 1. Install Required Tools

GpsSimul relies on standard C compilation tools and Git. Open your terminal and install them using your package manager.

Ubuntu/Debian: sudo apt update && sudo apt install git build-essential macOS: xcode-select –install 2. Download the GPS Ephemeris Data

A GPS simulation requires authentic satellite orbital data, known as an ephemeris file.

Download a Daily GPS Broadcast Ephemeris file (.26n format for the year 2026) from a public repository like NASA’s CDDIS or the IGN RSS feed. Save this file to your working directory. 🚀 Building and Running GpsSimul

Follow these step-by-step instructions to compile the source code and run your first simulation. Step 1: Clone and Compile

git clone https://github.com GpsSimul cd GpsSimul gcc gpssim.c -lm -O3 -o gpssim Use code with caution.

The -O3 flag optimizes the compilation for faster signal generation. Step 2: Generate a Static Location Signal

To generate a 30-second signal for a fixed location (e.g., Tokyo, Japan), run:

./gpssim -e brdc1500.26n -l 35.6895,139.6917,100 -d 30 -o static_gps.bin Use code with caution. Step 3: Generate a Dynamic Trajectory Signal

To simulate a moving vehicle, you must supply a user motion file containing time-tagged coordinates:

./gpssim -e brdc1500.26n -u trajectory.csv -d 60 -o dynamic_gps.bin Use code with caution. ⚙️ Command-Line Arguments Reference

Customize your simulation using these essential parameter flags:

-e : Specifies the input RINEX broadcast ephemeris file (Required).

-l : Sets static receiver coordinates (Latitude, Longitude, Ellipsoidal height).

-u : Path to a CSV text file defining a dynamic user motion path.

-d : Duration of the generated signal in seconds (Default is 300s).

-o : Path for the output binary signal file (Default is gpssim.bin).

-b : Sets the output sample bit depth, typically 1 or 16 bit. 🛰️ Transmission and Hardware Replay

The generated .bin file contains raw I/Q signal samples. To test physical hardware, you must stream this file through a Software Defined Radio (SDR). Replaying via BladeRF bladeRF-cli -s bladerf_tx.txt Use code with caution.

Your script should set the frequency to 1575.42 MHz (L1 Band) and the sample rate to 2.6 MHz. Replaying via HackRF

hackrf_transfer -t static_gps.bin -f 1575420000 -s 2600000 -a 1 -x 0 Use code with caution. ⚠️ Important Safety and Legal Notice

Radio frequency spoofing is highly restricted. Simulating GPS signals over the air can disrupt critical aviation, maritime, and civilian infrastructure.

Always use a shielded coaxial cable to connect your SDR directly to the receiver.

Never transmit GPS frequencies using an external antenna unless you are inside an RF-shielded chamber. To help customize this guide further, let me know:

What SDR hardware (HackRF, BladeRF, USRP) are you targeting?