Speed Dash 4+

Speed Dash - Accurate GPS Speedometer

Purpose

Speed Dash is designed to help users verify the accuracy of their vehicle's speedometer by comparing it with GPS-based speed measurements. Most vehicle speedometers have a built-in margin of error (typically showing 5-10% higher than actual speed), and this app allows you to see the difference in real-time.

Key Features

Real-Time GPS Speed: Displays your current speed based on GPS data

Multiple Units: Switch between km/h, mph, m/s, and knots

Speed History Graph: Visualizes speed changes over time

Altitude Tracking: Shows your current altitude and changes over time

Signal Quality Indicator: Displays GPS accuracy and signal strength

Location Coordinates: Shows your current latitude and longitude

Dark Mode Optimized: Clean interface that works well in all lighting conditions

How to Use

Open the app and grant location permissions when prompted

Mount your device securely in your vehicle

Start driving and observe both your vehicle's speedometer and the GPS speed

Toggle between different speed units using the unit indicator

View your speed history in the graph at the bottom of the screen

Compare altitude changes as you drive through varying elevations

Technical Details: GPS Speed vs. Vehicle Speedometer

Vehicle Speedometer Accuracy

Most vehicle speedometers are designed to display a speed that is slightly higher (typically 5-10%) than your actual speed. This is intentional and serves several purposes:

Legal protection: Manufacturers avoid liability from drivers inadvertently speeding

Tire wear: As tires wear down, speedometer readings can change

Safety margin: Encourages drivers to drive slightly under the speed limit

GPS Speed Measurement

GPS speed is calculated by measuring the distance traveled between satellite pings and is generally more accurate than mechanical speedometers:

Accuracy: Typically within 0.1-0.2 km/h (0.06-0.12 mph) when good signal is available

No mechanical variables: Not affected by tire size, wear, or pressure

Signal-dependent: Requires good satellite visibility for optimal accuracy

Factors Affecting Accuracy

GPS signal quality: Accuracy decreases in tunnels, dense urban areas, or heavy tree cover

Device position: Best results when device has clear view of the sky

Update frequency: The app updates speed multiple times per second for smooth readings

Requirements

iOS 18.3 or later

iPhone or iPad with GPS capability

Location Services enabled

Privacy

This app uses location services only when the app is active. No location data is collected or transmitted to external servers. Location data is only used locally to calculate and display your speed and altitude.