How the Real-Time Speedometer Works

Technical Overview

This online speedometer uses your device's GPS (Global Positioning System) and mathematical formulas to calculate your real-time speed directly in the browser. Below is a step-by-step explanation of how it works under the hood.

Step 1: GPS Location Access

When you click Start on the speedometer page, your browser asks for permission to access your location. The tool uses the JavaScript Geolocation API, specifically navigator.geolocation.watchPosition(), to continuously receive live GPS updates from your device.

• High-accuracy mode is enabled to improve precision.
• Your device's GPS chip provides latitude, longitude and timestamp data.
• If you deny permission, the speedometer cannot function.

Step 2: Receiving Position Updates

As you move, your device sends back a stream of position objects. Each update includes:

• Latitude – your north–south position on Earth.
• Longitude – your east–west position on Earth.
• Timestamp – the exact time the location was measured.
• Additional accuracy and metadata fields from the GPS sensor.

Step 3: Calculating Distance (Haversine Formula)

To compute how far you have traveled between two GPS points, the tool uses the Haversine formula, which calculates the great-circle distance between two points on a sphere:

• Converts latitude and longitude differences from degrees to radians.
• Uses Earth's radius (R ≈ 6,371,000 meters) as a constant.
• Computes the shortest path over the Earth's surface between both locations.

In code, this is implemented as a function that takes the previous and current GPS coordinates and returns distance in meters.

Step 4: Calculating Speed from Distance & Time

Once distance is known, speed is calculated using the basic physics formula:

• Speed = Distance ÷ Time
• Distance: meters traveled between two GPS readings.
• Time: difference between timestamps of the two readings (in seconds).
• Speed is first calculated in meters per second (m/s).
• Then converted to km/h by multiplying by 3.6, or to mph using the standard conversion factor.

Step 5: Real-Time Display & Animations

Every time a new speed is calculated:

• The numeric speed value on the dial is updated.
• The speedometer circle animates to reflect your current speed.
• The tool checks if this value is your new maximum speed.
• The reading is stored in a history array to compute average speed.
• Total distance is incremented by the newly calculated distance.

Step 6: Tracking Time, Distance, Max & Average Speed

In addition to instant speed, the speedometer page:

• Starts a timer when you press Start and shows elapsed time in minutes and seconds.
• Accumulates each small distance segment to show total distance traveled.
• Calculates maximum speed as the highest recorded speed value.
• Computes average speed based on all valid speed samples collected during the session.

Step 7: Unit Conversion (KPH & MPH)

The speedometer supports both kilometers per hour (km/h) and miles per hour (mph):

• All internal calculations are done in metric units (km/h and kilometers).
• When you switch to mph, the tool converts:
  • Speed from km/h to mph using the factor 0.621371.
  • Distance from kilometers to miles using the same factor.
• Switching units instantly updates all displayed values (current speed, max speed, average speed, and distance).