# How do I describe an XYZ velocity in a written sentence?

I'm creating a voice interface for Amazon Echo, providing status information regarding the International Space Station (ISS). I'm attempting to express the XYZ velocity of ISS.

Speed inquiry example request and response:

Q: How fast is ISS traveling?

A: ISS is traveling at 27,604 kilometers per hour. That's 17,153 miles per hour.

Of course, speed is different than velocity as speed knows no direction. How would I express the following in a sentence?

x velocity: 7.33 km/s

y velocity: 1.83 km/s

z velocity: -1.3 km/s

Here's my first attempt at it:

ISS is currently traveling at an x velocity of 7.33 kilometers per second, a y velocity of 1.83 kilometers per second and a z velocity of -1.3 kilometers per second. That's a speed of 27,604 kilometers per hour, or 17,153 miles per hour.

What is the more appropriate way to describe XYZ velocity or is this the best way?

• Maybe it is better to provide some sort of spherical coordinates instead? Because to talk about $x,y,z$ you have to define the position of each axis (I guess the origin is at the centre of the earth, but what is the orientation of the axis? ) You could instead provide 2 angles defined in some way that makes sense.. Just an idea :P – Ant May 22 '16 at 12:29
• That's a good idea. I'll have to work on the math aspect. The programming converts xyz to values needed to eventually get latitude, longitude and altitude in other areas. I suppose that could also mean that xyz isn't a good set of values to for humans to digest when talking about velocity. – Christopher Stevens May 22 '16 at 12:35
• You also need to pick a frame of reference to specify your velocity. – user_of_math May 22 '16 at 15:17