Timing Apps

App timing is a variation on the Timing Device method of timing. In this case the timing device is a tablet with a timing app, sending times over the mobile or WiFi network to results software. The advantages are:

• Built in mobile or wireless network
• Form factor (battery life, portability)
• Ubiquity - no need for custom devices, just load the app.

The Head of the River Race (HoRR) in the UK has developed its own custom tablet app, using the same approach as their laptop race timing software: How we time the Head of the River Race.

There are also several commercial tablet apps. These combine the timing with web-based results. An example is Webscorer, used by the Veterans' Head and Pairs Head.

Times are taken by using the touch screen to record the moment, and associating it with a competitor. The tablet app can hold the list of competitors, so you can either type in a crew number or select from a list. With Webscorer, the different options match the different ways you might need to take the time, for example: tap a competitor to record their time; tap a time and associate it with a competitor; tap several times and come back to them later.

Unlike the Timing Device, you cannot separate the tasks of clicking the time and associating the boat number. There's no way to use a separate hardware button to trigger the time. That means you have the same risk of operator overload as you do with Stopwatch timing.

A phone or tablet is also not a highly accurate timing device. The app relies on the internal clock. See Clocks for the problem with internal clocks. The clock is normally corrected at intervals from the mobile network, which causes the time to jump by small amounts. See NTP for the problems with time correction.

To solve this, Webscorer has an option to take the times from a dedicated timing device. In this case the timing device is responsible for the accuracy of the times, while the tablet is acting as the results computer: Webscorer with Startgate or Photocell.

One difficulty here is that the tablet has no hardware interface. You can't plug the timing device into it. The tablet relies on WiFi to receive the timing data, but the timing devices do not have mobile or WiFi outputs to send it. You need to set up a separate Wireless Local Area Network, and use a serial to ethernet connection to connect the timing device to the WiFi. When the tablet is connected to the local WiFi to rceive the timing data it cannot also be connected to the mobile network to send the data to the results system.

Tablet apps are a convenient form factor together with easy-to-use timing software. In a way, they are an updated version of laptop timing. They are very suited to Head races where sub-second accuracy is not required.

You can do some interesting experiments to test the accuracy of a tablet app:

• Emerald Time tells you the offset of your time from the NTP servers on the internet
• Emerald Timestamp enables you to tap a time and find its offset from NTP
• The reaction time tests should give you an idea of whether your times are different on a mobile than they are on a PC
• Try putting the phone or tablet in the fridge for a few hours, and see what the difference is in timing accuracy
• Try moving the phone or tablet from WiFI to Mobile to see what the difference is in timing accuracy.