Introduction

Based on experience and the knowledge provided from research, coaches can conduct their own analysis of divers' performances to identify current levels of performance as well as to see where improvements may be made. This may be merely observation of video taken informally at poolside with a hand held handicam or it may involve the use of software that enables more in depth analysis and quantifying the variables of interest to compare with values obtained by elite divers in international competition. These data are available on the database of this website. To obtain this quantitative information you need to use a software package such as 'Silicon Coach' or 'Quintic'. Irrespective of which software package is used for this analysis, it is essential that the video is recorded in a way that minimises errors. The following are considerations for recording video to be used for calculating the set of standard variables for springboard diving described in the previous papers.

Considerations for Collecting Video Data

Prior to data collection, you will need to investigate the venue, together with the venue manager, to establish what is possible and to ensure that special requirements can be met. The following need to be included in your planning.

• Permission: You need to have permission from the divers to be videod and analysed. This is a simple matter if you are only analysing your own divers. However, if you are analysing other divers you need to obtain the signed consent of divers and their coaches. Consent forms that include an explanation of the purposes of the analysis are required. If you are recording during competition you also need permission of the event organisers and pool manager. Your intentions to conduct the analysis should be made clear well before the event.
• Field of view: Following some practice at panning, the field of view should be set so that the diver is about half the height of the frame. Provided the panning camera is set on a tripod and maintains its orientation, information regarding the postures adopted during flight and their timing including the angle of entry, can be obtained.
• Ensure that the camera axis is perpendicular to the plane of motion: The ability to do this depends on the venue. At many diving venues, it is possible to have the camera axis perpendicular to the plane of motion of a diver's board work on the 3 m springboard. This usually means setting the camera in the spectator gallery. If all else is equal and it is possible to secure this position from either side, it is best to be on the side farthest away from the springboard to reduce perspective error. However, having the tower complex in front of the springboards is not desirable as the various platforms tend to obscure the view of the springboard action. In addition to ensuring that the camera axis is perpendicular to the plane of motion, ensure that the field of view has its upper and lower edges level. This can be achieved by lining up a known horizontal, for example, a level of a spectator gallery directly opposite your position.
• Access to power: If you are wanting to video continuously over a considerable period it is preferable to have continuous power to cameras rather than to rely on batteries. Check beforehand that power is available nearby, that cables can be run from the power source, and that the sockets and voltages are compatible. Sometimes pools have different sockets and voltages to comply with safety regulations. Check whether there are safety restrictions on using power near the side of the pool. For example, an isolating transformer may be required. When running cables, ensure that they are fixed in a way that eliminates risk of tripping.
• Shutter speeds and available light: For quantitative analysis of springboard and platform diving, a shutter speed of 1/500s or higher is desirable. Below this speed, accurately digitising the wrists and hands during the arm swing becomes difficult due to blurring. Depending on the camera, the lighting may be inadequate to use this speed without having a dull image that lacks contrast. Venues vary considerably in the brightness of the lights. Some venues are capable of increasing the light above the usual levels to cater to television coverage of events. It is essential to consider these aspects with the venue manager prior to data collection. It is generally not viable for you to supply additional lighting and it is not appropriate to have your own flood light from the side during competition. It may be necessary to select cameras based upon their ability to work at high shutter speeds in low light situations.
• Background and variability of light: Some pools have considerable light from outside the building. Thus, lighting can change with the time of day and with the weather. This needs to be assessed before the day of data collection. As well as the overall intensity of light, its direction needs to be considered. The quality of the image for digitising is better when light illuminates the diver from the same side as the camera. If the diver is between the camera and a light source, for example, if the camera is looking into windows on the other side of the pool, or if the background is very white, then the image of the diver will be dark and difficult to digitise. With the venue manager's permission, it may be possible to provide a better background, for example black cloth curtains. As a last resort, you could use 'backlight' compensation settings available on many modern video cameras. In any case, it is highly desirable to have pilot data collection sessions, across the range of possible conditions that could be encountered during the event, to ensure that the quality of the footage to be digitised is optimised.
• Linear scale information: Pieces of black tape can be placed on the side of springboards at 1 and 3 m from the board tip. It is also helpful to put a piece of black tape on the side of the tip with a small self-adhesive reflective dot.
• Fulcrum settings: You may wish to know the fulcrum settings used by your divers or by other competitors. This can be accomplished by having a recorder seated in the spectator area in line with the fulcrums. Pieces of black tape placed at settings of 3, 5 and 7 will assist the observer in identifying the fulcrum location. Depending on the data collection situation, divers could also be asked where they set their fulcrums.
• Date and/or time display: Whenever possible, the time should be displayed in the video frame being careful that it does not obscure any of the action. When more than one camera is used in the data collection, their time/date functions should be synchronised before data collection. Time information displayed in the frame makes it possible to quickly access a given performance for review or analysis.
• Framing rate: The framing rate that is required depends on the nature of the research. If is desirable to accurately quantify variables at precise events, for example, hip angle at the instant of last contact with the springboard, then the standard framing rate of video cameras (25Hz PAL or 30Hz NTSC) is clearly inadequate because postures can change markedly between frames. If your analysis software can split frames into fields, then the rate is effectively doubled (50Hz PAL or 60Hz NTSC).
• Staking and maintaining your claim: When collecting data at competitions, you must have permission from the meet organisers as to where your cameras will be positioned and what seats you will occupy. It is also essential to set up well ahead of time and maintain a physical presence with your camera(s) before the competition begins and between events. If you do not do this, your cameras may be moved and your seats occupied by spectators or TV personnel.
• Dive orders and dive scores: If collecting data at a competition, a list of the divers and the dives they are performing should be obtained. Comments can be written on this list to identify specific events and/or problems encountered during the data collection. As well, the time corresponding to the end of each round can be recorded. At the end of the competition, a copy of the scores awarded by the judges should be obtained.
• Videotape identification: Immediately following data collection, each videotape should be labelled to clearly identify its contents (e.g., meet, 1m, 3m, platform, gender of divers, rounds, date, camera view, etc.)
• Diver descriptive information: Divers' names, heights, weights and ages should be obtained. If heights and weights cannot be measured directly, reference to media guides or information submitted by coaches or team leaders to the competition officials may have to be used.