Train Speedometer

Choose your units and activity

Select km/h, mph, knots or m/s. Walking gives the dial a 30 km/h equivalent range; cycling uses 80 km/h. Passenger mode keeps the wider theme range. These change the display, not your measured speed.

Start GPS and check the signal

Press Start GPS and allow location access. The first position may not include speed. Wait for a fresh reading, and use Settings to inspect its source, position accuracy and age instead of assuming the device has stopped.

Pause, review and keep your summary

Pause when you finish. Review trip scrolls to the statistics below the dashboard. Download PNG for a branded snapshot or CSV for a spreadsheet. Reset asks before clearing an existing trip.

A walk, not a race

Use the walking range to see small changes more easily, then compare pace in minutes per kilometre or mile. Slow movement can be hard to separate from position drift, so treat a stop-start walking estimate as approximate rather than a fitness tracker record.

A cycling session

Set your phone securely before you leave. The cycling range keeps ordinary riding speeds visible without using the whole vehicle-scale dial. Review maximum speed, moving average and active time afterwards; do not handle the screen while riding.

A train or bus journey

As a passenger, compare the changing speed with the stops along your route. A tunnel can interrupt reception without interrupting the journey. We stop connecting measurements across long gaps so that a later position does not suddenly create a false distance jump.

Learning about motion

Try the demo to explore the needle, themes and unit conversions without sharing a location. A classroom can compare 10 m/s with 36 km/h, then discuss why a precise-looking number is not the same as a precise measurement.

Four units, one measurement

The engine keeps speed in metres per second. The display converts it using 3.6 for km/h, 2.2369362920544 for mph and 1.9438444924406 for knots. A change of units also changes the trip-distance label: miles for mph, nautical miles for knots, and metres or kilometres otherwise.

Ranges for different activities

Walking and cycling make the dial easier to read at everyday speeds. Passenger mode restores the classic, digital or railway 240 km/h range, the racetrack 500 km/h range or the airplane 1,500 km/h range. If speed exceeds a dial’s range, the number remains visible even though the needle reaches its limit. Coloured dial zones are decoration, not speed-limit advice.

Five appearances without losing your trip

Classic uses a needle; Digital favours a large numeric display; Railway, Racetrack and Airplane add their own scenes. Switching appearance within the tool keeps the same session. The related pages below let you open a particular dashboard directly.

Demo and live data stay separate

Try demo pauses GPS tracking and runs a simulated acceleration. It does not increase the real distance, maximum or moving average. The screen and PNG label the simulation, while the CSV remains a real-session summary. Stop the demo or press Resume GPS to return to measurement.

Elapsed, active and moving time

Elapsed time runs from the first accepted position, including pauses. Active time excludes a manual pause or stopped tracking. Moving time includes accepted movement intervals above 0.45 m/s. Moving average divides distance from those intervals by their duration; it is not an average over your entire outing.

Freshness and useful diagnostics

A speed becomes unavailable after ten seconds without a fresh position. Settings show the age of the last update, the browser’s permission state and whether speed came from the device or from consecutive positions. Position accuracy is a radius in metres, not a guarantee that the displayed speed is accurate to a particular amount.

Fullscreen, wake lock and HUD

Fullscreen gives the display more room; Escape exits on browsers that support it. Keep screen awake requests a screen wake lock while tracking, but support and battery policies vary. Mirror display flips the dashboard for a reflected HUD experiment; it is not an approved substitute for vehicle instruments.

A summary you can keep

The PNG combines the displayed speed, its live/demo/paused status, real trip statistics, time of export and ClockTools branding. CSV gives you labelled summary fields for a spreadsheet. Neither export includes a route trace or raw latitude and longitude. Your trip is held in this page’s memory, so save the summary before closing or reloading it.

Why a timetable is not a speedometer

Railway time and railway speed are closely related, but they measure different things. A timetable includes station stops, acceleration, signals and recovery time. Dividing the route distance by the scheduled duration gives a journey average, not the speed at every point.

Our passenger display shows the device’s current ground-speed reading. It can help you notice a departure, a steady section or an approach to a station, but it does not identify the line’s speed limit or communicate with the train’s control systems.

The Shinkansen’s changing scale of travel

The Tokaido Shinkansen opened on 1 October 1964 with the Series 0, whose maximum speed was 210 km/h. JR Central now lists up to 285 km/h for the Tokaido route.

This is a useful reason to distinguish a browser dial from a railway specification. Our 240 km/h scale is an interface choice, not a statement about all trains. High-speed routes need a wider visual range, and the passenger’s phone still needs a usable location signal.

Official reference: JR Central: Annual Report 2018 (PDF) · JR Central: Tokaido Shinkansen

A record run is not an everyday service

On 3 April 2007, the specially prepared TGV V150 reached 574.8 km/h in a record test. That figure should not be presented as the normal speed of a scheduled TGV journey. Test conditions and routine operations answer different questions.

Reception also changes along a rail route. Tunnels, covered stations and the carriage itself can interrupt location updates. A gap is not evidence that the train stopped. Treat a browser speedometer as a passenger observation tool, not a railway instrument or a way to certify a record.

Official reference: Alstom: TGV V150 Speed Record, 2007

The story began with a radio signal

Long before a phone could show a moving blue dot, researchers noticed that a satellite’s radio frequency changed as it moved towards or away from an observer. Observations of Sputnik in 1957 helped demonstrate how that Doppler shift could reveal an orbit. Reversing the problem suggested another possibility: if a satellite’s path was known, its signal could help locate the receiver. GPS grew out of a much longer history of radio navigation, engineering and timekeeping, rather than a single smartphone invention.

That history is useful when you look at our dial. The screen is the final, friendly layer of a measurement chain involving satellites, receivers, operating-system services and a browser. A beautifully animated needle cannot repair a weak signal at the start of that chain.

Why a location system needs exceptionally good clocks

GPS satellites broadcast timed signals. A receiver compares when a signal was sent with when it arrived to estimate the distance to each satellite. In the basic three-dimensional solution, at least four satellites are needed to solve for position and the receiver’s clock offset. Satellite clocks are therefore part of the measuring instrument, not merely a way to display the time of day.

The same infrastructure supports time transfer as well as navigation. NIST explains how GNSS signals help compare clocks across distant locations. ClockTools began with time tools, so this connection is especially fitting: the speed on this page depends on a world of coordinated timing even when all you see is a number in km/h.

Ground speed and the dashboard do not always agree

A vehicle speedometer usually infers motion from wheel or drivetrain rotation. Tyre size, pressure, calibration and the design of the instrument can affect that reading. A location-based estimate follows a different route: the device may report horizontal speed directly, or we may estimate it from the distance between accepted positions. Neither method makes our browser tool a calibrated reference instrument.

In an aircraft, the distinction becomes more important. Ground speed describes motion relative to the Earth; airspeed describes motion relative to the surrounding air. Wind can change the relationship between them. Our airplane theme does not measure airspeed, and a visually impressive aircraft dashboard should never be mistaken for a flight instrument.

Read the journey, not just the biggest number

Imagine two cyclists covering 12 kilometres. One rides steadily for 40 minutes; the other stops for a ten-minute conversation. Their moving averages may be similar, but elapsed time tells a different story. That is why we keep elapsed, active and moving time separate instead of hiding all three behind one average.

A practical pace example is 1.5 m/s: that is 5.4 km/h, or approximately 11 minutes 7 seconds per kilometre. But if your location uncertainty spans tens of metres, a short walk may not provide enough displacement for a reliable estimate. Watching the source, freshness and position accuracy is often more informative than collecting extra decimal places. Our summary helps you interpret what was measured, including the limits.