Building ice/speed skating timing system

One of my projects is building my own timing system for speed skating. I have some ideas of how to build this, but to be sure of the feasibility and needed components I decided to ask some help on reddit/arduino. It is a good description of the project too: In ice skating and speed skating they employ Photoelectric Retroreflective Sensors (lasers) to time passing over the start/finish line. As a hobbyist ice/speed skater I want to build such a system so we can organise competitions with our club, and time results precisely.

Floating point precision, in practice

Normally as a programmer Float’s are more than precise enough. During one of my projects however I had some serious headaches because of it. At start of the project I was rolling my own points in 3D-space, just a fancy wrapper around 3 Doubles. When I needed more vector powers (cross products, quaternations, rotation matrices) I switched to com.github.jpbetz.subspace.Vector3 from This Vector3 uses 3 Floats internally, which was fine, cause it wouldn’t make that much of a difference, I thought.

Strava, inline skating heatmaps

Inline skating is one of my favourite things to do during summer, and I love to explore new routes. With skates however the road quality is very important. If the asphalt has too much gravel the skates shake heavily and the experience is awful. Strava, logging activities for cycling and running has had Heatmaps for quite some time. Also their Route Planner integrates the same data and uses *popularity* to snap routes to frequently traveled roads.

Animating views on Android

Note to self: whenever you try to animate a view that is either GONE or has height 0 this will not work the first time. The moment the user touches the screen or an UI update is triggered only then will the animation start. Of course I found this Stack Overflow question about not starting animations, but the view was defined as being VISIBLE. I also explicitly made the view visible in code – just to be sure – but this was not enough.