Using the application myDartfish Express, you can capture speed and acceleration data generated by the MoveSense sensors during a live recording. The data are merged with the video and displayed in a graph. They can also be downloaded separately for further statistical analysis This article explains how to use myDartfish Express with the MoveSense sensors.
- The MoveSense sensors are very precise to calculate the speed and acceleration in an horizontal plane. Vertical movements are projected on the two-dimensional horizontal plane and the data are calculated on this plane
- Hits and shocks on the sensor create noise in the speed and acceleration data.
- The sensor provides more data (e.g. rotations around the axis) but only the speed and acceleration are supported in Dartfish for now. Let us know if you want to capture more data streams from the sensor.
- myDartfish license 360 or above
- Application myDartfish Express on an iOS device
- MoveSense Sensor (note: the application has not been tested with the Move Sense Sensor HR+)
Connecting the sensor to the app
- Launch the myDartfish Express application on your iOS device
- Go to my Videos
- Click on the camera icon on the top left to open the video recording module
- Click on the small remote control icon on the bottom right to scan for compatible sensors in the range of the mobile device. MoveVense sensors use a bluetooth connection low energy 4.0. If more than one device is found, the application will only let you select one of them
- Wait for the message "device detected and connected"
- A graph will appear on top of your application. 6 parameters will be displayed next to it.
- Their values start at 0.00 and are static for about 6 seconds. During that time the sensor is calibrated and should not be touched nor moved. Once the values start oscillating around 0, the calibration is done and the sensor can be used
- Start the video recording and the data will automatically be merged with the video
- The position of the graph can't be modified during a recording. This can be done after the recording, during the video playback
6 different data streams are integrated to the video. Acceleration is shown in meter per squared second and speed is displayed in meter per second
- axy: acceleration on the horizontal plane (displayed on the grap)
- vxy: speed on the horizontal plane (displayed on the graph)
- vx: speed on the x-axis in meter per seconde
- vy: speed on the y-axis
- ax: acceleration on the x-axis
- ay: acceleration on the y-axis
NB: the x axis is defined by the projection of the two screws on a horizontal surface during the calibration phase. The y-axis is perpendicular to this axis. The axis remains the same even if the sensor is rotated, as long as the calibration is valid
The vertical axis goes from -10 to 10 for the acceleration [m/s^2] and speed [m/s]. The horizontal axis goes from -10 to 2 seconds. Both axis cross at 0
Changing the synchronization and editing the graph
During the playback of a video that was recorded with data from the external sensor, it is possible to modify the size and position of the graph. You can also change manually the synchronization between the data and the video if you notice an offset
- Open your video
- Select the Selection drawing tool and click on the graph
- Use the squares to resize it.
- Click on the green "[Sync]" button to change the synchronization
- Press on the screen and drag your finger on the right or left to change the position of that data while staying at a fixed position in the video
- Click on the Check icon on the top right to validate the new synchronization
Download the data stream as a csv file
The data displayed on the video are automatically saved in a csv format. You can find them below the description of the video. If you move the video to a cloud collection or publish it on a dartfish.tv channel, the data will be kept with the video.