The most accurate method to start the clock in SprintTimer is to use the sound from the starting gun, either directly in Photo Finish or via Start Sender. You need a microphone that is placed close to the starting gun to get a sound that is significantly louder than the surrounding noice (cheering crowds, wind etc). But if you have an electronic starting gun an even better solution is to connect the starting gun directly to the headset jack on the iPhone/iPad.
Electronic timing is older than most people imagine and was used for the first time more than a hundred years ago at the 1912 Stockholm Olympics. Initially, the well-known telecom company Ericsson was tasked with developing the technology, but it was the Swedish inventor Ragnar Carlstedt who eventually delivered the final product. Using his expertise in electromechanics, he developed a system where reference clocks automatically started at the firing of the gun. Continue reading A brief history of timing
This entry complements the ”Zoom and add on lenses” post below and is therefore relevant also to those who don’t have the iPhone7+. The main disadvantage with using an iPhone/iPad for photo finish is that it has a wide angle camera. You have to stand pretty close to the finish line and the relative distance to the different lanes varies quite much. This means that it is difficult to set a slice width that is optimal for all runners.
Photo finish images are becoming more common. And since they not are what they might seem to be, so some explanations might be useful. The following is therefore a description of how a photo finish is created and interpreted. It is hopefully useful both if you want to time an event yourself, or if you just are an interested spectator how want to understand the photo finishes that are published.
This is the ”nerdiest” entry in the blog so far 🙂 But if you are prepared to do some basic electronics wiring and maybe some very simple programming, you will be rewarded by being able to start SprintTimer with high accuracy by any mean imaginable (light, IR, pressure, switches etc etc). It also allows you to add other start signals like strong sound, light flashes etc. If you don not feel up to it yourself, you might have a friend, student or athlete who thinks it is fun to tinker with a project like this.
Start Sender is a convenient way to send the starting time from the start to Photo Finish at the finish line. The problem is that the direct communication between two devices has a limited range (30m-40m) and to cover e.g. a 100 m race you need an external WiFi network. And that is not always available outdoors on a stadium. A solution could be to set up temporary router, and since there might not be a power plug nearby, it should preferably be a battery powered one.
Using the sound from e.g. a starting gun is the most accurate way to start the clock in SprintTimer. A problem, however, is that the start often is so far away that the sound drowns in the background noise. To transfer the sound to SprintTimer at the finish you can use a microphone with an extension cable or a Walkie Talkie. If you have two devices and access to a network you can also use Start Sender, which is a flexible, and almost as accurate option as sending the sound. Using a Walkie Talkie is pretty common and usually the best solution for really long distances, e.g. in rowing and kayaking. But the most stable and accurate solution for distances up to 100-150 m is a sound cable. Continue reading Making a long sound cable
With SprintTimer I claim that the accuracy is almost as good as a high end professional fully automatic timing equipment. This article presents some measurement I made to test this claim. Since the the most accurate method to measure a race is to to start the clock with a sound and the finish with Photo Finish, I have focused on that set up, but also tested some other variations.
All iPhone and iPad cameras have fairly wide angle lenses. This means that you must stand pretty close to the participants to fill out the image when recording a Photo or Video Finish. Sometimes this is an advantage (e.g. indoors), but in most cases it is the oposite. In many water sports like rowing and kayaking it can be difficult to get close to the finish line. And if the participants have different lanes, like in a 100 m sprint, standing close makes it impossible to set a slice width that fits all runners. This because the runners moves with very different speed as seen by the camera.