An electronic starting gun is a useful tool since it is entirely risk-free and lets you control how loud the sound should be. It can also be connected directly to SprintTimer, as described in an earlier post. This makes it insensitive to external noise, and you can set the SprintTimer sound detection to ”always on.” But while a gun is not very expensive, it still costs from around $200. So if you are on a budget, or like DIY projects, you can build one yourself. That might sound hard, but it actually just a question of pretty basic wiring and you can get the components for under $10. It will also be more flexible than commercial guns since you can decide what type of sound you want and how to trigger the start.
This post might be a bit technical, but can help you understand how a smartphone or computer measures time.
Every smartphone and computer has a clock, so measuring time shouldn’t be a problem? Well, that is true if you want to know the time of the day within a second or so. But if you’re going to take milliseconds into account, it can become trickier. The clocks in smartphones are controlled by an oscillator, e.g. a crystal, in the same way as an electronic watch. Unfortunately, do the manufacturers prioritize cost and energy consumption over very high accuracy when picking oscillators (Apple is no better or worse than others in this respect).
For any timing tool the best accuracy is achieved by measuring the time from the side, and in line with the finish line. A big disadvantage though is that it can be difficult to identify the competitors. Hip numbers can be a solution, but is not always practical. But with SprintTimer you have another solution that maybe not is so obvious. If you have access to an extra iPhone or iPad you can use that as a frontline camera synchronised with the timing camera.
Motion detection is an important feature in SprintTimer. In Video Finish it helps to reduce the number of frames that you have to shift through. In Motion Finish it is the key factor for measuring time. So I thought that explaining how it works might help you apply it successfully. The first thing to realize is that it not really is motion detection, but rather change detection; the motion creates changes in the image that are detected.
Sprint tests can be conducted in more ways than ordinary races. The different setups in SprintTimer therefore come in handy, for example, you have the option to choose from either convenient ”timing gates” or the more accurate Photo Finish.
Many tests are over a 10-40 m distance, which is favourable since it means that you might use Start Sender without an external network. It is usually possible to connect two iPhone/iPads directly to each other over 30 m (40 m with luck). Below I have described some alternative setups that hopefully can inspire you to find the best configuration for your test.
Continue reading Sprint Testing
One of the strengths of SprintTimer is that is an ”all in one” solution with a camera, display and result generation in one small, neat smartphone package. But it is sometimes also a weakness, it can prevent you from placing the camera in an optimal place since you must access it after each race. Or you might not have time get the results after each race if they come too frequently. The recent updates of SprintTimer, however, has made it possible to place one iPhone/iPad as a remotely controlled finish line camera and handle everything from one or two other devices.
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 noise (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 an iPhone with dual camera. The main disadvantage of 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 are not 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 that want to understand the photo finishes that are published.
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 in a stadium. A solution could be to set up a 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 most accurate method to measure a race is to start the clock with a sound and the finish with Photo Finish, I have focused on that setup, 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 opposite. 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 move with very different speed as seen by the camera.