FOOTBALL CONTACT DETERMINATION This innovation patent application is associated with Provisional Patent Application No. 2012902416 and the entire contents of the provisional patent specification are incorporated 5 herein by this cross reference. This invention relates to determining whether or not a contact of a football with a goal post or the like has occurred. 10 In Australian Rules football, if the football has been kicked by a player and the ball touches a goal post, a goal is not scored even if the ball has crossed the goal line between the two spaced goal posts (but a 'behind' or point is scored). Another rule of the game provides that if the kicked football touches one of the outermost secondary or 'behind' posts without having first bounced, a point or behind is not scored even if the ball passes between that behind post 15 and the nearer spaced goal post - rather the ball is deemed to have been kicked out of bounds 'on the full' and a penalty or 'free kick' is awarded to the opposing team. If the kicked ball has bounced and then touches the behind post, there is no score even if the ball passes between that behind post and then next adjacent goal post - the ball is considered to have passed out of bounds and is thrown by an officiating umpire back into the playing field. 20 In all of these possible situations, an error made by an officiating goal umpire in deciding whether or not the ball has touched the post can lead to an incorrect score being awarded or perhaps a failure to award a score when the team was entitled to be so awarded. Such errors in scoring arising from errors of officiating umpires can change the course of the football 25 game and even alter the final outcome of the game. There have been in the past decisions made by officiating umpires which have sometimes been clearly incorrect when the incident has been closely examined from images captured by a television broadcaster replaying the incident in slow motion and from different viewing positions. At other times even such replays of video sequences can still leave the issue undecided but nevertheless controversial. 30 It is an object of the present invention to provide a method and apparatus for enabling determination with greater accuracy whether a football, during play of a football game, has touched a post defining one side of the goal zone or a behind post defining one side of the secondary scoring zone. 2 According to the present invention in a first aspect there is provided a method of enabling determination whether a football, during play of a football game, has touched a post defining one side boundary of the goal zone or a post defining one side boundary of a secondary 5 scoring zone, the method including the steps of: providing a sound detector in operative association with the post so that sound produced by substantially any impact or significant momentary contact of the football with the post during play of the football game will be registered by the sound detector, generating a contact signal by the sound detector or in response to operation of the sound 10 detector upon the occurrence of an impact or momentary contact of the football with the post, transmitting signals generated by or in response to operation of the sound detector to a storage means and storing them in the storage means as sound data signals, capturing and storing video images of the football game during play of the game including images of the football in motion (including in flight, and bouncing or rolling along 15 the ground, and being carried by a player participating in the game) during play of the football game, displaying for viewing by an observer the video images from a time period in the game which included an incident of interest involving the football being in proximity to the post, and, in close synchronism with the display of the video images, manifesting the sound 20 information embodied in the stored sound data signals in a manner enabling the observer to compare the synchronicity and the characteristics of any manifested sound information with the displayed images of the football in closest proximity to the post and thereby determine if the football has touched the post. 25 Using this method involving capturing and displaying video images of the incident with a closely synchronised manifestation of the captured sound information, the contact, or absence of contact, of the football with the post can be determined with greater certainty than by observing the video images alone. 30 Preferably the manifestation of the sound information embodied in the stored sound data signals is selected from: generating an audio output of the stored sound data, the audio output comprising a processed manifestation of the stored sound data, the processing comprising at least one of the processes of amplification, filtering, and frequency shifting; and 3 creating and displaying a visible representation of the stored sound data, the visible representation being selected from e displaying a trace of the sound signal with time comprising one axis of the trace and signal magnitude on an orthogonal axis, and 5 e a visible indication whether the captured sound data has satisfied predetermined criteria indicative of the football having contacted the post. When the football game comprises an Australian Rules Football game, preferably the sound detector is located in or is mounted on one of the goal posts for detecting sound transmissions 10 along the post arising from contact of the football with the post. In the preferred embodiment, there are at least two sound detectors mounted in or on the post at different longitudinal positions along the length of the post, the two detectors being mounted in or on the structural body of the post and being separated along its length whereby the time interval between detection of the particular sound by the two spaced detectors provides information about the 15 location of the football contact along the length of the post relative to the locations of the detectors, the method including computing from the time interval and displaying for the observer information about the deduced location of the football contact with the post. According to the present invention in a second aspect there is provided an apparatus for 20 enabling determination whether a football, during play of a football game, has touched a post defining one side boundary of the goal zone or a post defining one side boundary of a secondary scoring zone, the apparatus including: at least one sound detector provided in operative association with the post so that sound produced by substantially any impact or significant momentary contact of the football with 25 the post during play of the football game will be registered by the sound detector, a signal generator operative to generate a contact signal upon the occurrence of an impact or momentary contact of the football with the post when registered by the sound detector, a storage means operative to receive signals generated by or in response to operation of the sound detector and to store them as sound data signals, 30 video apparatus operative to capture and store video images of the football game during play of the game including images of the football in motion (including in flight, and bouncing or rolling along the ground, and being carried by a player participating in the game) during play of the football game, display means operative to display for viewing by an observer the 4 video images from a time period in the game which included an incident of interest involving the football being in proximity to the post, and sound manifesting means operative to manifest the sound information embodied in the sound data signals stored in the storage means in close synchronism with the display of video 5 images by the display whereby the observer can compare the synchronicity and the characteristics of sound information manifested with the images of the football presented by the display means including images of the football when in closest proximity to the post, thereby enabling determination if the football touched the post during play of the football game. 10 The present invention in this second aspect enables the observer operating or using or monitoring or watching the apparatus or system in operation to compare the synchronicity and the characteristics of manifested sound information with the displayed images of the football moving in closest proximity to the post and thereby the observer can determine if the football 15 has touched the post. Further aspects of the method and apparatus of the present invention will be described with reference to the accompanying drawings which schematically illustrate some aspects of possible apparatus utilising the invention. 20 Fig. 1 illustrates a football goal post or behind post with at least one sound detector which generates a signal and a transmitter which relays the signal to a remote receiver for storage, processing and manifestation. 25 Fig. 2 illustrates an apparatus receiving sound data signals from the post(s) and for data processing, data storage, and providing signals for sound manifestation. In the following descriptions of possible and preferred features of apparatus and methods according to the invention, references to the drawings will be made where helpful, but the 30 invention is not limited to anything shown in or described with reference to the drawings. In one possible system the manifestation of the sound information embodied in the stored sound data signals comprises generating an audio output of the stored sound data. That is, the stored sound data signals are used to generate by a speaker or the like an audible sound. The 5 audible output may be substantially unmodified captured sound information, apart from being amplified. However preferably the stored sound data is first processed by filtering so as to substantially attenuate or remove sound or vibration propagating in the vicinity, particularly in the post where there will be such sounds and vibrations that are not characteristic of the 5 sound encountered upon a football contacting the post. The sound characteristics of a football contacting the post can be empirically determined enabling the filtering parameters to be defined so as to enhance discrimination of the sound arising from a ball-post contact e.g. by the "sound validity verification" module in Fig. 2. The processor in Fig. 2 also shows a "video generator" module responsive to the "sound validity verification" module and 10 operative to generate for display an indication whether the validity verification module has determined a strong, moderate, or weak correlation between the characteristics of the actual sound detected and the empirically determined expected characteristics of a ball-post contact. For example, if there is a strong correlation indicating near certainty of a ball-post contact, a positive indicator in the video display can be generated (e.g. the word "YES", or a green 15 coloured sound trace) with a moderate correlation, the word "POSSIBLE" and/or amber coloured sound trace may be generated, and with a weak correlation the word "NO" and/or red coloured sound trace may be generated. Likewise suitable amplification can be provided to enhance discrimination. 20 Another form of processing may comprise frequency shifting of the detected sound. For example if the detected sound is in a part of the inaudible spectrum or perhaps in a part of the audible spectrum more difficult to discriminate, the sound arising from the ball-post contact may be detected, recorded and also frequency shifted so that when replayed through the audible output it can be more readily discriminated. If replayed at a slower speed (like a slow 25 motion video replay) the sound may be frequency shifted to ensure the audible sound is in the human hearing frequency spectrum. Alternatively, or in addition, the manifestation of the sound information embodied in the stored data signals may include creating and displaying for viewing by the observer a visible 30 representation of the stored sound data. In one particular embodiment for example, the visible representation may comprise displaying for viewing the sound data such as by displaying a trace of the sound signal with time comprising one axis of the trace, normally the horizontal axis, and signal magnitude on an orthogonal axis (vertical axis preferably - this is shown at the bottom of the video display in Fig. 2). In Australian patent specification No. 199952942 6 (patent No. 753622) in the name of Allan Plaskett (hereinafter referred to 'Plaskett') there is described in detail methods and apparatus for converting a detected sound arising from a cricket ball touching a cricket bat and displaying the sound data captured, for example a trace on a screen or monitor of the sound signal. The same types of sound signal capture and 5 processing described in Plaskett can be used with any necessary modifications given the different nature and sound characteristics in the field of the present invention. The contents of Plaskett are incorporated herein by this cross reference for the purpose of providing disclosure of apparatus for implementing certain aspects of the present system, particularly sound signal processing and manifestation. 10 Fig. 2 also schematically illustrates there is a "synchronisation" between the video processing and the sound processor so the output video display includes any necessary adjustments for time shifts between video frame capture (effectively instantaneous) and sound detection and capture. In particular, the time of travel of the sound in the post from the ball-post contact 15 point to the detector can be significant so time shifting of the sound manifestation relative to the video display (particularly in a slow motion video replay) provides the adjustment necessary for assessment of synchronicity of the sound generation and the ball-post contact. As an alternative (or in addition) to displaying a trace of the sound signal, the visible 20 representation of the stored sound data may comprise a visible indicator whether the captured sound data has satisfied pre-determined criteria indicative of the football having contacted the post. For example the sound spectral characteristics or 'signature' of a football touching the post may be predetermined and the processing system may test detected sounds to discriminate as legitimate sounds arising from a ball-post contact from those sounds that do 25 not have those same characteristics or signature. If the remaining sounds that satisfy the characteristics or signature specified fall within a time window coincident with video images captured for the football moving in close proximity to the post, a visible indicator may be provided to affirm that a legitimate contact signature or characteristic has been detected. The time window for example may be defined by an operator selecting and inputting (using 30 conventional peripherals (mouse, keyboard, etc.) of the video processor) start and finish points for a sequence of captured video image frames during which the ball is seen to be moving in close vicinity of the post. Although the sound detector may be located elsewhere so as to the operative to detect sounds arising from ball-post contacts, it is preferred that the sound detector is located by 7 mounting it in or on the post for detecting sound transmissions in or along the post arising from the relevant contact. The sound detectors can be any suitable form such as piezoelectric transducers or other sound detecting microphones or the like mounted in or on the post so as to detect and generate signals upon detecting sound vibrations in the post. Such vibrations 5 can arise from many sources including ambient noise, contact of players with the post, vibrations in the post transmitted from the ground, etc. Because there are many sources of sound, sometimes very loud sound, filtering of frequencies that would not characterise the ball-post contact sought would be desirably performed. Also if desired, sound cancellation technology may be used to capture sound information from a vicinity of the post, but not 10 arising from a ball-post contact, with such background sound data being electronically 'subtracted' from the sound captured by the detector associated with the post. Such sound cancelling technology is known for example in hearing protective equipment used by workers in noisy environments. Filtering may include sound volume "filtering" by seeking a sound discernable above the volume of background noise (which can be substantially constant in the 15 short interval, perhaps 0.1 to 0.2 seconds, in which a ball-post contact sound is being sought) - e.g. an average sound volume in the target time interval can be calculated to define an envelope, and a short sound signal of a volume outside that envelope can indicate the ball post contact. Preferably there are at least two sound detectors mounted in or on the post at different 20 longitudinal positions along the length of the post (Fig. 1). Goal posts are usually provided with protective padding along the lower part of its height to lessen risk of injury to a player colliding with the post and, with such posts, at least one detector may be mounted in or on the padding so as to detect ball-post contact involving the padding and at least one detector is mounted in or on the structural body of the post (e.g. metal, timber, plastics, ceramic, 25 composite, or other structural material). By providing two (or more ) detectors mounted in or on the structural body of the post and separated lengthwise, the time interval(s) between detection of the particular sound by the respective spaced detectors provides information about the location of the ball contact along the length of the post. Therefore the apparatus may have processing means (e.g. that labelled 30 "contact height algorithm" in Fig. 2) which computes from the time interval between the detection of the sound by the two spaced detectors an approximate location of the ball-post contact. For example, one detector may by located at or in proximity to the lowest part of the post and the other located at or in proximity to the highest point of the post whereby the computation of the contact location along the major part of the length of the post between the 8 two detectors can be achieved by utilizing the times of detection by the two detectors of the particular sound arising from a ball-post contact travelling within the post. For example, sound travels in aluminium at somewhat over 6000 metres per second, so that sound will travel the length of a six metre high post made of aluminium in about one millisecond. 5 Arrival time differentials of much less than one millisecond can be detected whereby the approximate position of the source of the sound detected by the two detectors can be determined from the time interval between the two detector signals. For example, if the two detectors detect a sound from a ball-post contact substantially simultaneously, the contact of the ball with the post is substantially mid-way between the two detectors. If the top most to detector first detects the sound and the bottom most detects the sound one millisecond later, the contact will have been very close to the top detector. Other materials from which posts are manufactured will have different sound propagation speeds and this can be incorporated into the programming. 15 In another embodiment there may be a plurality of detectors spaced along substantially the length of the post at pre-determined spaced locations. The amplitudes of the sound detected at each detector can vary depending on the distance of the detector from the source of the sound. This can arise from attenuation of the sound as it travels in the material of the post. The system therefore can include computation from the detected signal amplitudes at the 20 plurality of detectors an indication of the approximate location of the contact of the ball with the post. With this amplitude utilisation, the system is believed to require calibration because variations in the sensitivity of the variety of detectors and variations in the sound transmission parameters of the post will affect the detected amplitudes. Also the sound coupling between the posts and the mounting of each detector may have a bearing on the sensitivity of the 25 detector to the sounds travelling within the post and hence the amplitude of the detected sound. The calibration may comprise generating test contacts of an article, particularly a football, with the post at various locations along its length and measuring the detected sound amplitudes at each of the plurality of detectors. Using the known locations of the test contacts of the football with the post, the system can calculate weightings or adjustments in a 30 computational algorithm for relating the relative sound amplitudes detected to the contact locations known in the calibration process. In practical use, the indication of the deduced or calculated location of the ball contact where this is determined from detected sound amplitudes and/or from time intervals between 9 multiple detections by multiple detectors on the one post, that indication of calculated location is preferably displayed for the observer. The system is preferably operative to thereby enable the observer to compare the displayed computed or deduced location of the ball contact with the displayed video images in the relevant time period which includes the suspected ball-post 5 contact. By generating (by the "video display simulation generator" in Figure 2) and by providing a display of the calculated location of the ball contact, eg by an artificial highlight or glint or pointer or icon superimposed on an image of the post approximating the computed contact location (see the "calculated height indicator" icon in Fig. 2), any significant inconsistency between the approximate location of the ball contact observable in the video 10 images and the location deduced or computed from the detected sound signals can be apparent. This can enable the observer to eliminate spurious determinations of ball-post contacts due solely to a coincidental substantial synchronicity of a candidate sound transmission within the post and a video image of the football passing the post. For example, if the video image shows the football moving in close proximity to the post towards its upper 15 end whereas the sound detectors and associated processing system detect and compute an approximate position of the source of a detected candidate sound as, say, one metre above the ground along the height of the post, the candidate sound is readily discriminated from one that would have arisen from an actual contact of the ball with the post 5-6 meters above the ground. 20 In patent specification GB 2457674 in the name of Allan Plaskett there is described a system using at least four microphones to determine a location of an impact between a cricket ball and a cricket bat and then generating an icon presented on a visual display representing the calculated location of the sound producing impact. That system in the Plaskett specification 25 is adapted for use with fixed cameras so that the generation and presentation of the icon can be superimposed on replayed video signals from the fixed camera field of view. In the present invention, video capturing cameras are likely to be moving and capturing video images from multiple directions so that the moving football is visible from at least one of the captured video sequences. In the present invention therefore the indication of the computer 30 football contact location is preferable on a simulated image of the post, e.g. presented in the visual display alongside the video images (see the "post simulation" image in Fig. 2). The Plaskett specification GB 2457674 nevertheless gives information illustrating how the calculated football contact position can be determined and visually presented in the present invention. 10 It will be appreciated that various modifications and variations of the method an apparatus as described herein can be devised without departing from the spirit and scope of the invention as defined in the following claims. 5 11