Rosso Speedometer
Guides
Practical notes on GPS speed, units and using a speedometer app safely.
How to Choose a Simple Speedometer App for iPhone
Just want your speed, with no map, ads or trip log? A checklist for picking a simple GPS speedometer app on iPhone, including how to read the privacy label.
km/h, mph, Knots and m/s: Speed Conversion Chart
Exact formulas and a quick chart for converting km/h, mph, knots and m/s, based on NIST definitions, plus how to turn speed into running pace (min/km).
How Accurate Is GPS Speed? Why It Jumps, Freezes and Wobbles
Phone GPS is typically accurate to about 4.9 m under open sky. Why GPS speed jumps in cities, freezes in tunnels and wobbles at walking pace, and how to help it.
Why Your Car Speedometer and GPS Speed Disagree
Car speedometers must never read below your true speed, so most read a little high. What UN Regulation No. 39 and Japan's rules say, and which speed to follow.