Service Communautaire d'Information sur la Recherche et le Développement - CORDIS

A 3-D local positioning system has been developed with the use of two cameras and an innovative positioning algorithm

The LPS system is an innovative 3D positioning system suitable for educational applications. It can be used for conducting indoor or outdoor school experiments and combines playful learning with teaching laws of Newton physics. The system is simple in its construction easy to implement and calibrate and it is accompanied from special developed software that can process the captured data. It has been extensively used for over a year in field trials in four schools in Greece Germany and Austria with very promising results. The architecture of the system is briefly the following.

The system is composed 2-CCD cameras, which observe the area within which the experiment or the activity will take place. The typical test area for the 2-camera system is 10mX10mX3m. This means that the system will be able to identify and record the position of an object (ball) at least within this area. The accuracy of the system for the above field of view is around 5-10cm. Both cameras are connected to a PC, which is located nearby. The system records the trajectory of the ball and the relevant players or any other type of activity during the proposed experiment. The cameras are connected to a personal computer through the parallel ports. Two frame grabber PC cards are used. Each camera has the ability to record 50 frames/sec. The proposed system will be able to capture 25 active frames per second. This is due to the parallel frame grabber's architecture that is utilized. Since both cameras must be synchronized and each frame must be recorded at the same time, the final capacity of the system is diminished from the 50/sec frames of the individual camera to the 25/sec. Additionally to the position of the observation object, the relevant time parameter is recorded simultaneously for each frame. By this way a few minutes video with the experiment/activity can be produced. For the presentation and the processing of the recorded frames, a user-friendly software sub-module has been developed within the software platform of the whole Lab of Tomorrow project. The student will be able to recover to the PC screen the frames from both the cameras, which are referring to the same time parameter.

Then the student will identify the object in each frame and with the help of the mouse will mark it producing the relevant set of x, y, z coordinates. With the use of these coordinates, a software program developed by ICCS, produces the absolute coordinates (xo, yo, zo) of the ball/object. The coordinates will be written on a file along with the time parameter. Having recorded all these parameters, the student will be able to reconstruct the trajectory of the object. The acceleration data coming from the sensors that are embedded in the ball or on the students (please also refer to result no2), can be also viewed and combined with the data of the LPS helping by this way the student to make very interesting observations with experiments that involve free choice activities. It should be noticed that the LPS system is fully synchronized with the rest system that is described in result no 2 and this enables the user to make optimum use of all the acquired data Summarizing, the proposed software program not only is able to reconstruct the trajectory of the observation element, but it is also able to calculate and present graphically the other related parameters (time, acceleration etc.).

The LPS system is a laboratory prototype system that is able to reconstruct the 3D movement of any object within a certain field of view during an experiment or a joyful activity of the students with a very good accuracy. It is a very helpful educational tool for the teaching of physics in schools with the use of real life experiments. 3D movements can be analysed and this is unique because all the commercially available similar products can track objects only in two dimensions. The software of the system has been built in such a way in order to guide and facilitate the student to reconstruct the object's trajectory. The only disadvantage of the system that has been identified during its trials is that the set-up and calibration time needed for its proper operation is extended. This problem can be a draw back for the installation and the operation of the system in an everyday basis within a normal school curriculum. In the future, the system should be more easily set-up and calibrated and this whole process should be performed from the school staff with a standardized procedure.

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