GPS Altimeter & Speedometer

A portable device capable of displaying GPS coordinates, altitude, and speed on a small OLED screen.
Perfect for hiking, cycling, or mountain activities where you want to know your position and pace without relying on a smartphone.

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Features

• Reads GPS data (latitude, longitude, altitude, speed).
• Displays information on a 128x64 OLED display (via I2C).
• Runs on a battery (3.7 V Li-ion + TP4056 charging module recommended).
• Improved altitude readings by combining GPS and barometric sensor (BMP280/BME280).
• Implements a Kalman filter to fuse GPS and barometric data:
  • GPS provides the absolute reference altitude.
  • Barometer provides smooth, fast relative changes (stairs, slopes, climbing).
  • The Kalman filter merges both, correcting GPS “jumps” and barometric drift.
• Extendable and customizable for additional sensors or logging functions.

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Hardware Components

• ESP32 (tested on ESP32-S3, but adaptable to other boards)
• GPS module (e.g., NEO-6M, NEO-7M, NEO-8M, u-blox M8N)
• OLED Display (128×64, SSD1306, I2C)
• Barometric sensor: BMP280 or BME280
• Battery (e.g., 18650 Li-ion)
• 3D printed box

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Wiring

• GPS → ESP32

  • GPS TX → ESP32 GPIO 48 (RX2)
  • VCC → 3.3V or 5V (depending on module)
  • GND → GND

• OLED → ESP32

  • SDA → GPIO 20
  • SCL → GPIO 21
  • VCC → 3.3V
  • GND → GND

• Barometric Sensor (BMP280/BME280) → ESP32 (I2C)

  • SDA → GPIO 20
  • SCL → GPIO 21
  • VCC → 3.3V
  • GND → GND

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Software

Libraries Required

Install these from the Arduino Library Manager:

• TinyGPS++
• Adafruit SSD1306
• Adafruit GFX
• Adafruit BMP280
• SimpleKalmanFilter

How the Fusion Works

• The barometer gives very stable readings but is affected by weather changes.
• The GPS gives absolute altitude but with noisy, sometimes jumpy data.
• The Kalman filter continuously smooths the barometric altitude and, every few seconds, corrects it towards the GPS reference.
• The result is a fused altitude: smooth like the barometer, but anchored to the true GPS level.

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Example Code

The example sketch included in this repo:

• Initializes GPS on Serial2 (GPIO 48).
• Reads coordinates, GPS altitude, and speed with TinyGPS++.
• Reads barometric altitude from BMP280.
• Fuses the two values with a Kalman filter.
• Displays latitude, longitude, GPS altitude, barometric altitude, and fused altitude on the OLED.