METHOD AND SYSTEM FOR DETERMINING THE DISTANCE COVERED BY A SWIMMER IN A POOL DURING AN APNEA SEQUENCE

Abstract

METHOD AND SYSTEM FOR DETERMINING THE DISTANCE COVERED BY A SWIMMER IN A POOL DURING AN APNEA SEQUENCE The invention relates to a method (9) for determining the distance covered by a swimmer (2) during an apnea sequence in a pool (3). According to the invention, the method comprises the steps implemented by a calculation unit (10) aimed at: - obtaining (91) positioning data when the swimmer is on the surface of the water, these data being derived from a positioning signal originating from beacons arranged at the edges of the pool and / or from a box worn by the swimmer, - obtaining (92) movement data when the swimmer swims under the surface of the water, these data originating at least from an accelerometer embedded in the box; - counting (93) the number of turns made by the swimmer (2) from the movement data; and - determining (94) the distance covered by the swimmer (2) from the positioning data and the number of turns counted.Fig. 4.

Description

Title of the invention: METHOD AND SYSTEM FOR DETERMINING DISTANCE CROWDED BY A SWIMMER IN A POOL DURING A FREE-DIVING SEQUENCE Technical field

[0001] The present invention relates to a method and a system for determining the distance covered by a swimmer in a pool, and more particularly during an apnea sequence. STATE OF THE PRIOR ART

[0002] In the field of swimming or dynamic apnea, it is always difficult to determine precisely the distance covered by the swimmer, whether swimming on the surface of the water or under the surface of the water (i.e. in apnea).

[0003] For open water swimming (i.e. in a lake or sea for example), the use of a GPS-type satellite tracker worn by the swimmer can provide satisfactory results.

[0004] However, as soon as one tries to measure the distance covered in a swimming pool with a GPS tracker, determining the distance covered becomes more difficult, and provides less precise, or even relatively erroneous, results.

[0005] Indeed, the use of a GPS tracker is only possible outdoors. And, even in the case of use in an outdoor swimming pool, the measurement of distance by a GPS tracker has a significant margin of error. More precisely, as soon as the swimmer swims under the surface of the water, the GPS tracking malfunctions and the measurements are therefore erroneous. In addition, the use of the GPS tracker is not possible in the case of an indoor swimming pool.

[0006] To overcome this problem, it is known to use devices, such as example of sports watches, which are capable of counting the lengths completed by the swimmer in the pool. However, there are many cases in which the length count is erroneous. Indeed, these devices generally use an accelerometer and / or a gyroscope to detect that the swimmer is moving (by detecting the movement of the swimmer's arm wearing the sports watch) and to determine a change in the swimmer's behavior (for example, a change in stroke or a stop). It should be noted that each of these changes in behavior leads to the counting of an additional length. However, in apnea, swimming movements can lead to an untimely and erroneous counting of a length by these devices. Similarly, if you change strokes during a length, if you stop during a length or if you turn around before the edge of the pool, these devices make no distinction and therefore count an additional length for each of these events.

[0007] Furthermore, if the swimmer moves without using his arms, for example only thanks to the movements of his legs, possibly aided by a floating board, the swimmer's movement is not detected and no length is therefore counted.

[0008] Finally, these sports watches require manually setting the length of the pool for the count to be carried out. However, the choice of lengths is generally restricted to the standard lengths of swimming pools (25m, 33m or 50m for example) and the use of these watches in pools of different dimensions (for example private pools) is therefore not possible.

[0009] Therefore, determining the length traveled by a swimmer in a pool using these methods is not optimal.

[0010] There is therefore a need to provide a solution offering a simple and precise determination of the distance covered by a swimmer in a pool, and more particularly when the swimmer practices apnea. Statement of the invention

[0011] An object of the present invention is to propose a method for determining the distance covered by a swimmer during an apnea sequence which is precise and simple to implement.

[0012] To this end, a method is proposed for determining the distance covered by a swimmer during an apnea sequence in a pool, said pool comprising two edges separated by a length and at least one transmitter-receiver beacon, each beacon being arranged at one of the two edges, said swimmer wearing a box comprising a transmitter-receiver and an accelerometer.

[0013] According to the invention, the method comprises the steps implemented by a calculation unit, aiming to:

[0014] - obtain positioning data of said swimmer when he is on the surface of the water of said basin, said positioning data being derived from a positioning signal from said at least one beacon and / or said box;

[0015] - obtaining movement data of said swimmer when swimming under the surface of the water of said basin, said movement data coming at least from said accelerometer;

[0016] - count the number of turns made by said swimmer while leaning against said edges of said basin from said motion data; and

[0017] - determining the distance covered by said swimmer during said apnea sequence in said basin by combining said positioning data and said number of turns counted.

[0018] In this way, it is possible to obtain in a simple and precise manner the distance covered by a swimmer in a pool, whether swimming on the surface of the water or underwater. The invention therefore does not require the use of underwater tracking technologies which are expensive, difficult to implement and poorly suited to implementation in a swimming pool.

[0019] According to a particular aspect, the step aimed at obtaining said positioning data of said swimmer when he swims on the surface of the water of said pool comprises the sub-steps aimed at:

[0020] - receive, by said at least one beacon or by said box, a signal from positioning emitted by said box or by said at least one beacon when the swimmer moves on the surface of the water of said pool;

[0021] - determine, by said at least one beacon or by said box or by said unit calculation, the positioning of said swimmer in said pool from said positioning signal;

[0022] - generate, by said at least one beacon or by said box or by said unit calculation, positioning data of said swimmer in said pool from the positioning determined previously.

[0023] According to another particular aspect, the positioning signal is a wirelessly transmitted signal.

[0024] According to yet another particular aspect, the positioning signal is an Ultra Wide Band radio signal.

[0025] According to a particular aspect, the step aimed at determining the distance covered by said swimmer during said apnea sequence in said pool comprises the sub-steps implemented by said calculation unit aimed at:

[0026] - detecting a point of entry of the swimmer under the surface of the water;

[0027] - detecting a point of exit of the swimmer on the surface of the water;

[0028] - if no turns were counted between the entry point and the exit point, calculate a second distance separating the entry point and the exit point to obtain the distance covered by said swimmer during said apnea sequence;

[0029] - if at least one turn was counted between the entry point and the exit point:

[0030] - calculate a third distance separating the entry point and the edge following said entry point depending on the direction of advancement of said swimmer;

[0031] - calculate, from the length separating the two edges between which said turns were made by said swimmer swimming under the surface of the water and said number of turns counted, a fourth distance covered by the swimmer under the surface of the water of said pool;

[0032] - calculate a fifth distance separating the exit point and the edge following said exit point depending on the direction of advancement of said swimmer;

[0033] - calculate, from the third distance, the fourth distance and the fifth distance, the distance covered by said swimmer during said apnea sequence.

[0034] According to another particular aspect, a total distance traveled by said swimmer in said pool between a starting point and the exit point is equal to the distance traveled by said swimmer during said apnea sequence added to a first distance traveled by said swimmer on the surface of the water of said pool between said starting point and said entry point, said first distance being calculated from said positioning data.

[0035] The invention also relates to a system for implementing the method for determining the distance covered by a swimmer during an apnea sequence in a pool as described previously, said pool comprising two edges spaced apart by a length and said system comprising: - at least one transmitter-receiver beacon, each beacon being arranged at one of said two edges of said basin; - a transmitter-receiver box worn by said swimmer, said box comprising an accelerometer-type sensor; - a suitable and configured computing unit for:

[0036] - obtain positioning data of said swimmer when he is on the surface of the water of said basin, said positioning data coming from at least one beacon and / or said box;

[0037] - obtaining movement data of said swimmer when swimming under the surface of the water of said basin, said movement data coming at least from said accelerometer;

[0038] - count the number of turns made by said swimmer while leaning against said edges of said basin from said motion data; and

[0039] - determining the distance covered by said swimmer during said apnea sequence in said basin by combining said positioning data and said number of turns counted.

[0040] The invention also relates to a computer program product comprising instructions for implementing, by the calculation unit, the method as described previously, when said program is executed by a processor of the calculation unit.

[0041] Finally, the invention also relates to a storage medium storing a computer program comprising instructions for implementing, by the calculation unit, the method as described previously, when said program is executed by a processor of the calculation unit. Brief description of the drawings

[0042] The above-mentioned features of the invention, as well as others, will appear more clearly on reading the following description of an embodiment and its variants, said description being made in relation to the attached drawings, among which:

[0043] [Fig. 1] schematically illustrates a method for determining the distance covered by a swimmer during an apnea sequence in a pool according to the invention;

[0044] [Fig.2] schematically illustrates the sub-steps implemented in step obtaining swimmer positioning data from the method of [Fig.l];

[0045] [Fig.3] schematically illustrates the sub-steps implemented in the step of determination of the distance traveled by the swimmer of the method of [Fig.l];

[0046] [Fig.4] is a schematic top view of a basin showing the movement of a swimmer from the starting point to an entry point below the surface of the water and an exit point without having made a turn by leaning against an edge of the pool;

[0047] [Fig.5] is a schematic top view of a basin showing the movement of a swimmer from the starting point to an entry point below the surface of the water;

[0048] [Fig.6] is a schematic top view of a basin showing the movement of a swimmer at the moment when he reaches the surface of the water again after having made one or more turns while leaning against the edges of the pool;

[0049] [Fig.7] is a schematic side view of a basin showing the displacement of a swimmer performing a breath-hold sequence;

[0050] [Fig.8] schematically illustrates an example of hardware architecture of a computing unit according to the invention; and

[0051] [Fig.9] is a graph schematically illustrating the shaping of the intensity from an accelerometer signal during a turn.

[0052] DETAILED DESCRIPTION OF AN EXAMPLE OF EMBODIMENT

[0053] [Fig.l] schematically shows a method 9 for determining the distance covered by a swimmer during an apnea sequence in a pool according to the invention.

[0054] More particularly, the pool 3 has two edges 31 separated by a length D between which the swimmer 2 moves. It is obviously understood that the pool 3 has more edges 31 to form the pool, which can be rectangular in shape for example.

[0055] An apnea sequence is defined here by a movement of the swimmer 2 in the pool 3 under the surface of the water. As illustrated in [Fig.7], the apnea sequence begins when the swimmer 2 dives, that is to say from the moment when the swimmer 2 finds himself under the surface of the water represented at the entry point PI which also defines the moment from which the swimmer 2 then moves under the surface of the water. The swimmer 2 therefore then moves underwater (that is to say in apnea) until he returns to the surface of the water at an exit point P2. The exit point P2 defines the end of the apnea sequence.

[0056] Before the entry point PI, swimmer 2 may move on the surface of the water, between a starting point PO and the entry point PL

[0057] When moving underwater, it is considered that the swimmer 2 moves generally in a rectilinear manner between two edges 31 of the pool 3. For example, the swimmer 2 moves generally in a straight line in a delimited space called a “water line”. As illustrated in Figs. 4 to 6, a water line 32, having a length D, extends between two edges 31 and can be delimited laterally by a floating buoy 33 on the one hand and by an edge 31 or another floating buoy 33 on the other hand.

[0058] The swimmer 2 can also make back and forth movements underwater between the edges 31 of the pool 3. It is considered here that the swimmer 2 therefore makes a turn underwater (i.e. without returning to the surface) at each edge 31. In general, the swimmer 2 takes support and pushes against the edge 31 during a turn.

[0059] The method 9 can be implemented by a system 1 which comprises: - at least one transmitter-receiver beacon 11 arranged at one of the edges 31 of the basin 3; - a transmitter-receiver box 12 worn by the swimmer 2, the box 12 comprising an accelerometer-type sensor; and - a calculation unit 10.

[0060] Although the invention can operate with a single beacon 11 arranged at one of the edges 31 of the pool 3, the system 1 preferably comprises two beacons 11 which are each arranged at one of the opposite edges 31 of the pool 3. In particular, the beacons 11 are arranged such that the distance separating them is equal to the length D between two edges 31 of a water line. If the distance separating two beacons 11 arranged on opposite edges 31 is not equal to the length D, a calibration of the system can be implemented in order to optimize the accuracy of the measurements. Preferably, a beacon is arranged at the ends of each water line in order to optimize the accuracy of the measurements. Other beacons 11 can also be arranged at the angles / corners of the pool 3.

[0061] The beacons 11 are said to be transmitter-receiver in the sense that they are adapted to transmit a positioning signal to the housing 12 and to receive a positioning signal transmitted by the housing 12.

[0062] In the case where the system only implements a single beacon 11, it is appropriate to ensure that the housing 12 is generally always oriented towards the beacon 11 in order to optimize the transmission (transmission and reception) of the positioning signal between the housing 12 and the beacon 11.

[0063] The implementation of two beacons 11 makes it possible to ensure better transmission of the positioning signal between the housing 12 and the beacons 11, regardless of the direction of advancement of the swimmer in the pool 3.

[0064] As described previously, it is therefore possible to provide that a box 12 communicates with a single beacon 11. Or, to improve the accuracy of the positioning data which will be described below, it is possible to provide that the box 12 communicates with at least two beacons 11. Each box 12 and each beacon 11 have an identifier which makes it possible to ensure a non-erroneous measurement.

[0065] The housing 12 worn by the swimmer 2 is preferably positioned under the swimmer's swimming cap, at the front of the skull and just above the forehead. For example, the housing 12 may be integrated into the swimming cap of the swimmer 2. This positioning makes it possible to optimize the quality of the data collected by the housing 12, as described in more detail below. In addition, such a positioning of the housing 12 still makes it possible to detect the movements / displacements of the swimmer 2 even when the swimmer is not using his arms (unlike a sports watch worn on the wrist of the swimmer 2).

[0066] It is understood, however, that the case 12 worn by the swimmer 2 could be positioned on the wrist, the waist or even the foot of the swimmer 2.

[0067] As for the beacons 11, the housing 12 is said to be a transmitter-receiver in the sense that it is adapted to transmit a positioning signal to one or more beacons and to receive a positioning signal coming from one or more beacons 11.

[0068] The computing unit 10 can be embedded in the box 12 worn by the swimmer 2, in one of the beacons 11, in a computer positioned at the edge of the pool 31 or in a remote server, for example.

[0069] As illustrated in [Fig.l], the method 9 according to the invention comprises the steps implemented by the calculation unit 10, aiming to:

[0070] - obtain 91 of the positioning data of swimmer 2 when he is (or moves) on the surface of the water of the pool 3, the positioning data coming from a positioning signal coming from the beacon(s) 11 (hereinafter use of the expression “the beacons” even if only one beacon can be used as described previously) and / or from the box 12;

[0071] - obtain 92 of the movement data of swimmer 2 when he is (or is moving) below the water surface of pool 3, motion data from at least the accelerometer;

[0072] - count 93 the number of turns made by swimmer 2 while leaning against the edges 31 of the basin 3 from the movement data; and

[0073] - determine 94 the distance covered by swimmer 2 during the apnea sequence in pool 3 by combining positioning data and the number of turns counted.

[0074] The step 94 of determining the distance covered by the swimmer 2 during the apnea sequence takes into account the length D separating the edges between which the swimmer 2 moves and makes his turns.

[0075] In this way, it is possible to determine in a simple and precise manner the distance covered by a swimmer in a pool. Indeed, the beacons 11 are capable, by communicating with the box 12 worn by the swimmer, of determining and therefore tracking the position of the swimmer 2 within the pool 3 in order to calculate the distance he has covered. Furthermore, the method is capable of detecting changes of direction (i.e. turns) made by the swimmer at the end of the pool (i.e. at the edges 31) thanks in particular to the accelerometer embedded in the housing 12 worn by the swimmer 2. Thus, and since the distance between the beacons is known, it is possible to determine the distance covered by the swimmer 2 during an apnea sequence from the positioning data coming from the beacons and / or the housing 12 and from the detection of the turns made by the swimmer 2 while leaning against the edges 31 of the pool 3.

[0076] As previously indicated, the accelerometer data is used to determine whether a movement or change of direction made by swimmer 2 is a turn made while leaning against an edge 31 of the pool (i.e., a turn with a push against the edge of the pool 31) or whether it is another movement not requiring a turn to be counted. For example, if swimmer 2 stops and starts again or makes a half-turn in the lane (i.e., without leaning against an edge 31 of the pool), it is possible to detect that the turn was not made at an edge because the accelerometer data does not correspond to reference data corresponding to a turn. Thus, method 9 does not count this movement of swimmer 2 as a turn in order to avoid the determination of the distance covered by swimmer 2 during an apnea sequence being erroneous.In other words, the accelerometer ensures that the turn is made by leaning against an edge (which means that the swimmer has moved to the edge 31 of the pool) to ensure optimal accuracy in determining the distance traveled by swimmer 2 during a breath-hold sequence.

[0077] [Fig.9] schematically illustrates a first curve C1 representing the shaping of the intensity of the accelerometer signal during a turn performed by leaning against an edge 31 of the pool 3 by the swimmer 2 and a second curve C2 representing the shaping of the intensity of the accelerometer signal during a turn not performed against an edge 31 of the pool 3 by the swimmer 2 (i.e. without having leaned against an edge 31 of the pool 3). The vertical axis represents the intensity I of the accelerometer signal which is expressed in mV / g (millivolt per g where g represents the acceleration) while the horizontal axis represents the time T expressed in ms (milliseconds).

[0078] It is understood that the signal of the intensity of the accelerometer is represented here schematically and after processing of the latter. The processing of the signal of the accelerometer is conventional and is therefore not described in detail here because it is not part of the invention and a person skilled in the art could implement it from the prior art, in particular by referring to the work “Sensors in industrial instrumentation” by Georges Asch (Dunod edition).

[0079] It can be seen from this graph that the curve Cl of a turn made while leaning against an edge 31 of the pool 3 has an intensity I that is significantly higher than the curve C2 of a turn made in the middle of the pool 3. In this example, it can be noted that after 500 ms, the intensity of Cl is four times higher than the intensity of C2.

[0080] From numerous tests carried out by the applicant, it was concluded that it was possible to consider that a turn made without leaning against an edge 31 of the pool 3 could not have an intensity measured by the accelerometer greater than a threshold value Vs. The threshold value Vs is for example between 280 and 320 mV / g, and preferably around 300 mV / g. Thus, it is possible to distinguish a turn made by the swimmer 2 by leaning against an edge 31 (which means that he went to the edge 31 of the pool 3) from a turn made during a length (i.e. before reaching the edge 31) in order to count or not this turn in the determination of the distance covered by the swimmer 2 in the pool 3.

[0081] As a substitute or in addition to this threshold value Vs, it is possible to use the slope (in %) of each curve C1 and C2. In this case, it is possible to consider that a turn not made by leaning against an edge 31 of the basin 3 cannot have a value greater than a threshold slope value Vps. The threshold slope value Vps is for example between 25 and 30%, and preferably approximately 27%.

[0082] More precisely, and as illustrated in [Fig.2], step 91 aimed at obtaining the positioning data of the swimmer 2 when he swims on the surface of the water of the pool 3 comprises the following sub-steps aimed at:

[0083] - receive 911, by the beacons 11 or by the box 12, a positioning signal emitted (continuously or at regular frequency) by the box 12 worn by the swimmer 2 or by the beacons 11 when the swimmer 2 moves on the surface of the water in the pool 3;

[0084] - determine 912 (continuously or at regular frequency), by the beacons 11 or by said box 12 or by said calculation unit 10, the positioning of the swimmer 2 in the pool 3 from the positioning signal;

[0085] - generate 913, by the beacons 11 or by said box 12 or by the calculation unit 10, positioning data of swimmer 2 in pool 3 from the positioning determined previously.

[0086] In this way, it is possible to simply and precisely determine the position of swimmer 2 in pool 3 in order to generate positioning data for swimmer 2. This positioning data, relating to the position of swimmer 2 when the latter moves on the surface of the water, then makes it possible to simply calculate the distance traveled on the surface by swimmer 2.

[0087] More particularly, the positioning data are obtained from the speed or propagation time of the positioning signal between the housing 12 and the beacons 11 (or vice versa).

[0088] Preferably, it is the beacons 11 which receive 911 the positioning signal emitted by the housing 12, which determine 912 the position of the swimmer 2 in the pool 3 and which generate 913 the positioning data. As indicated previously, the positioning data are then transmitted to the calculation unit 10. The beacons 11 therefore comprise means for transmitting this positioning data to the calculation unit 10. Such transmission means are conventional and are therefore not described in detail here.

[0089] Preferably, the positioning signal is a wirelessly transmitted signal. More particularly, the positioning signal is an Ultra Wide Band (UWB) radio signal. UWB signals make it possible to obtain an accuracy of the order of cm, which makes it possible to provide an accurate determination of the distance traveled by the swimmer 2. In addition, UWB is particularly suitable for indoor use.

[0090] It is understood, however, that other wireless signal transmission technologies (such as WIFI® or Bluetooth® in particular) could be implemented.

[0091] Although the measurement accuracy offered by UWB is optimal when the swimmer moves on the surface of the water, the disadvantage is that UWB signals are not transmissible in the water. This is the reason why the housing 12 worn by the swimmer here incorporates an accelerometer in order to determine the distance traveled by the swimmer under the surface of the water.

[0092] The use of the UWB radio signal and the accelerometer of the housing 12 is complementary here to ensure a simple and precise determination of the distance covered by the swimmer 2 during an apnea sequence.

[0093] As illustrated schematically in [Fig.3], step 94 aimed at determining the distance covered by swimmer 2 during the apnea sequence comprises several sub-steps implemented by the calculation unit 10. To facilitate the understanding of these sub-steps, [Fig.7] illustrates the different distances measured or calculated.

[0094] Step 94 optionally comprises a sub-step 940 of detecting the start of the apnea sequence at a point PO. The starting point PO is preferably located at an edge 31 of the pool 3. However, the beacons 11 are capable of detecting whether the starting point PO is offset from the edge, if applicable. The starting point PO can be triggered automatically, for example when the accelerometer detects a movement of the swimmer 2, or manually, by triggering the swimmer 2.

[0095] Step 94 includes a sub-step 941 of detecting an entry point PI of the swimmer 2 under the surface of the water. For example, the detection 941 of the entry point PI can be carried out by detecting the loss of the positioning signal and, in addition, when the housing 12 includes a pressure sensor, by detecting a change in depth of the housing 12 worn by the swimmer 2. Other complementary ways of detecting the entry point PI can be envisaged.

[0096] Step 94 optionally includes a sub-step 942 of determining a first distance DI traveled by the swimmer 2 on the surface of the water of the pool 3 between the starting point PO and the entry point PI from the positioning data. This sub-step 942 therefore takes into account the positioning data obtained using the beacons 11 and the box 12.

[0097] It should be noted that the first distance DI may be zero if the swimmer 2 immediately dives underwater, pushing against the edge 31 located at the starting point PO, for example. In this case, the starting point PO and the entry point PI are the same. Otherwise, the first distance DI is non-zero, for example if the swimmer pushes on the edge 31 but remains on the surface and then dives, or if the swimmer 2 dives from outside the pool and enters under the surface of the water at a distance from the edge 31.

[0098] Step 94 includes a sub-step 943 of detecting an exit point P2 of the swimmer 2 at the surface of the water. For example, the detection 943 of the exit point P2 can be carried out by detecting the recovery of the positioning signal and, in addition, when the housing 12 includes a pressure sensor, by detecting a change in depth of the housing 12 worn by the swimmer 2 down to a zero depth. Other complementary ways of detecting the exit point P2 can be envisaged.

[0099] Then, depending on the number of turns counted in step 93 of method 9, the distance D* traveled by swimmer 2 under the surface of the water between the entry points PI and exit points P2 is determined.

[0100] Thus, if no turn has been counted between the entry point PI and the exit point P2, step 94 comprises a sub-step aimed at calculating 951 a second distance D2 separating the entry point PI and the exit point P2 to obtain 953 the distance D* covered by the swimmer 2 during the apnea sequence, which can be carried out directly from the positioning data.

[0101] If at least one turn has been counted between the entry point PI and the exit point P2, step 94 comprises the sub-steps aimed at:

[0102] - calculate 961 a third distance D3 separating the entry point PI and the edge 31 following the entry point PI against which it is about to make a turn according to the direction of advancement A of swimmer 2. The direction of advancement A of swimmer 2 is known since it is, in principle, identical to the direction of movement of swimmer 2 between the starting point PO and the entry point PL In all cases, the movement data from the accelerometer can be used to determine the direction of advancement A of swimmer 2.

[0103] - calculate 962, from the length D separating the two edges 31 between which the turns were made by swimmer 2 swimming under the surface of the water and the number n of turns counted in step 93 of method 9 to obtain 963 a fourth distance D4 virtually covered by the swimmer under the surface of the water of pool 3. More precisely, calculation 962 involves multiplying the length D by the number n of turns counted in step 93 of method 9. The fourth distance D4 is considered to be a distance virtually covered by the swimmer since the exit point P2 is not necessarily located at an edge 31 of the pool. In other words, the swimmer may not have covered the full length D between the edges 31 of pool 3. It is therefore then necessary to:

[0104] - calculate 963 a fifth distance D5 separating the exit point P2 and the edge 31 following the exit point P2 against which swimmer 2 is about to make a turn according to the direction of advancement A of swimmer 2. When swimmer 2 swims the entire length in apnea and emerges from the water at the edge 31, the fifth distance D5 can be zero. The direction of advancement A of swimmer 2 is known since the number of turns is counted from the entry point PL In any case, the movement data from the accelerometer can be used to determine the direction of advancement A of swimmer 2.

[0105] - calculate 964, from the third distance D3, the fourth distance D4 and the fifth distance D5, the distance D* covered by swimmer 2 during the apnea sequence. More precisely the calculation 964 of the distance D* covered by swimmer 2 during the apnea sequence involves the addition of the third D3 and fourth D4 distances from which the fifth distance D5 is subtracted.

[0106] In this way, the distance D* traveled during an apnea sequence, which is expected in apnea competitions for example, can be determined simply and with great precision. Indeed, the combination of a detection of the entry points PI and exit points P2, with the determination of the position of these entry points PI and exit points P2 via the positioning data and with the determination of the distance traveled by the swimmer under the surface via the movement data provided by the accelerometer makes it possible to avoid the derivations observed in the techniques of the prior art to ensure optimal precision.

[0107] If one wishes to determine the total distance Dt traveled by the swimmer on the surface and under the surface of the water from the starting point PO and until the end of the apnea sequence (i.e. until the exit point P2), it is sufficient to add the distance D* and the first distance Dl. In other words, the total distance Dt traveled by swimmer 2 on the surface and in apnea in pool 3 is equal to the distance D* traveled by swimmer 2 during the apnea sequence added together, the first distance Dl representing the distance traveled by swimmer 2 on the surface before the entry point PI.

[0108] Furthermore, by repeating the method 9 according to the invention for each apnea sequence (and adding the first distance D1 if desired), it is possible to simply and accurately determine the total distance traveled by a swimmer 2, whether on the surface (taking into account the first distance D1) and / or underwater. In other words, it is possible to determine a total distance traveled by a swimmer performing a plurality of successive apnea sequences. To do this, it is sufficient to add the distance traveled by the swimmer 2 during each apnea sequence. Thus, when two apnea sequences follow one another (sequences n and n+1), it is possible to consider that the exit P2 of sequence n then becomes the starting point PO of sequence n+1.

[0109] The system 1 may further comprise a pressure sensor which may be used to capture the vertical trajectory (i.e. the change in depth) of the swimmer 2 in the water during the apnea sequence. In other words, the pressure sensor makes it possible to obtain a graphical representation of the sinusoid of the swimmer 2 along the horizontal and vertical axes (representation of the depth on the vertical axis and of the time on the horizontal axis). This information is particularly widely used by freedivers and / or swimmers. Similarly, the system 1 may further comprise a gyroscope and a magnetometer which may be used to detect the heading, i.e. the direction and orientation, of the swimmer 2.

[0110] The housing 12 may provide other sensors (such as a temperature sensor for example) and optionally a satellite tracking chip, of the GPS type for example, in order to complete the measurement of the distance covered by the swimmer, in particular when the swimmer is outdoors.

[0111] The housing 12 is furthermore waterproof. In particular, the housing 12 does not contain air and is filled with a dielectric oil which in particular makes it possible to provide optimal precision of the pressure measurement.

[0112] Alarm means, such as a vibrator or a beeper emitting a tone, can also be implemented to give indications to the swimmer 2 (for example when he reaches a speed limit, depth limit, etc.).

[0113] It is possible to provide, in particular in order to optimize the autonomy of the housing 12, to deactivate the emission of the positioning signal by the housing 12 when the swimmer moves under the surface of the water. Thanks in particular to a pressure sensor, it is possible to detect when the swimmer 2 begins to return to the surface so as to reactivate the emission of the positioning signal by the housing 12. This reactivation can for example be triggered, taking into account the pressure measurement associated with the ascent curve (pressure curve), when the swimmer 2 reaches a determined depth, for example 30 cm, or when a low speed, or even zero, is detected.

[0114] Similarly, reactivation can for example be triggered when the movement speed is less than or equal to a determined speed.

[0115] Furthermore, the transmission of the movement data from the box 12 to the beacons 11 (or to the calculation unit 10) is carried out when the box 12 worn by the swimmer 2 is on the surface.

[0116] The calculation unit 10 is adapted to collect and / or determine, in particular but not exclusively: the unique identifier of the boxes 12 and / or the beacons 11, the total swimming time on and / or underwater, the time of a slide, the time between two immersions, the distance covered on the surface and / or underwater, the average speed, the instantaneous speed, the trace / curve of the course in 2D or in 3D if there is more than one beacon at the edge of the pool, the number of ascents / exits to the surface of the water, the intensity of the accelerations, the number of changes of direction (turns), the variations in depth (sinusoidal curve made underwater), the intensity and direction of the movements of the swimmer's head under and / or out of the water when the box 12 is fixed on the head of the swimmer 2, etc.

[0117] The system 1 and the method 9 of the invention can be used for aquatic activities carried out in a pool, such as in particular but not exclusively for all dynamic apnea disciplines, for underwater hockey, for swimming and for synchronized swimming.

[0118] [Fig.8] schematically illustrates an example of hardware architecture making it possible to implement, in the form of electronic circuitry, the calculation unit 10 according to the invention.

[0119] According to the example of hardware architecture shown in [Fig.8], the computing unit 10 comprises, connected by a communication bus 200: a processor or CPU (Central Processing Unit) 201; a RAM (Random Access Memory) 202; a read-only memory 203, for example of the ROM (Read Only Memory) or EEPROM (Electrically Erasable Programmable ROM) type, such as a Flash memory; a storage unit 204, such as a hard disk HDD (Hard Disk Drive) or a storage media reader, such as an SD (Secure Digital) card reader); at least one I / f interface manager 205. The I / f interface manager 205 allows the calculation unit 10 to communicate via a wide area network and to interact with the beacons 11 and / or the box 12 worn by the swimmer 2.

[0120] The processor 201 is capable of executing instructions loaded into the RAM 202 from the ROM 203, from an external memory (not shown), from a storage medium (such as an SD card), or from a communication network. When the computing unit 10 is powered on, the processor 201 is capable of reading instructions from the RAM 202 and executing them. These instructions form a computer program causing the processor 201 to implement all or part of the method described herein.

[0121] The storage unit 204, or the RAM 202, is capable of storing a local database 206 storing in particular the positioning data and the movement data described previously.

[0122] All or part of the method described here can thus be implemented in software form by executing a set of instructions by a programmable machine, for example a DSP (Digital Signal Processor) type processor or a microcontroller, or be implemented in hardware form by a machine or a dedicated electronic component (chip) or a set of dedicated electronic components (chipset), for example an FPGA (Field Programmable Gate Array) or ASIC (Application Specified Integrated Circuit) component. Generally speaking, the calculation unit 10 comprises electronic circuitry adapted and configured to implement the method described here.

[0123] The method described above can be implemented in software form by executing a set of instructions by a programmable machine, for example a DSP ("Digital Signal Processor" in English) or a microcontroller, or be implemented in hardware form by a machine or a dedicated component, for example an FPGA ("Field-Programmable Gate Array" in English) or an ASIC (" Application-Specific Integrated Circuit (ASIC) in English). In general, the computing unit 10 comprises electronic circuitry configured to implement the method previously described.

[0124] It should be noted here that [Fig.8] represents a hardware architecture of a single computing unit 10. Some of the different constituent elements of the computing unit 10 can be distributed in different computing devices included in a computing cloud.

Claims

Claims

1. Method (9) for determining the distance covered by a swimmer (2) during an apnea sequence in a pool (3), said pool (3) comprising two edges (31) separated by a length (D) and at least one transmitter-receiver beacon (11), each beacon (11) being arranged at one of the two edges (31), said swimmer (2) wearing a housing (12) comprising a transmitter-receiver (121) and an accelerometer, said method (9) comprising the steps implemented by a calculation unit (10) aimed at: - obtaining (91) positioning data of said swimmer when he is on the surface of the water of said pool (3), said positioning data coming from a positioning signal coming from said at least one beacon (11) and / or from said box (12); - obtaining (92) movement data of said swimmer when swimming under the surface of the water of said pool (3), said movement data coming at least from said accelerometer; - counting (93) the number of turns made by said swimmer (2) while leaning against said edges (31) of said pool (3) from said movement data; and - determining (94) the distance covered by said swimmer (2) during said apnea sequence in said pool (3) by combining said positioning data and said number of turns counted.

2. Method (9) according to claim 1, characterized in that said step (91) aimed at obtaining said positioning data of said swimmer (2) when he swims on the surface of the water of said pool (3) comprises the sub-steps aimed at: - receive (911), by said at least one beacon (11) or by said box (12), a positioning signal emitted by said box (12) or by said at least one beacon (11) when the swimmer (2) moves on the surface of the water of said pool (3); - determining (912), by said at least one beacon (11) or by said box (12) or by said calculation unit (10), the positioning of said swimmer (2) in said pool (3) from said positioning signal; - generate (913), by said at least one beacon (11) or by said box (12) or by said calculation unit (10), data of

3.

4.

5.

6. positioning of said swimmer (2) in said pool (3) from the positioning determined previously. Method (9) according to claim 2, characterized in that said positioning signal is a wirelessly transmitted signal. Method (9) according to claim 3, characterized in that said positioning signal is an Ultra Wide Band radio signal. Method (9) according to any one of claims 1 to 4, characterized in that said step (94) aimed at determining the distance covered by said swimmer (2) during said apnea sequence in said pool (3) comprises the sub-steps implemented by said calculation unit (10) aimed at: - detect (941) an entry point (PI) of the swimmer (2) under the surface of the water; - detect (943) an exit point (P2) of the swimmer (2) on the surface of the water; - if no turn has been counted between the entry point (PI) and the exit point (P2), calculate (951) a second distance (D2) separating the entry point (PI) and the exit point (P2) to obtain (952) the distance (D*) covered by said swimmer (2) during said apnea sequence; - if at least one turn was counted between the entry point (PI) and the exit point (P2): - calculate (961) a third distance (D3) separating the entry point (PI) and the edge (31) following said entry point (PI) as a function of the direction of advancement (A) of said swimmer (2); - calculate (962), from the length (D) separating the two edges (31) between which said turns were made by said swimmer (2) swimming under the surface of the water and said number (n) of turns counted, a fourth distance (D4) covered by the swimmer under the surface of the water of said pool (3); - calculate (963) a fifth distance (D5) separating the exit point (P2) and the edge (31) following said exit point (P2) as a function of the direction of advancement (A) of said swimmer (2); - calculate (964), from the third distance (D3), the fourth distance (D4) and the fifth distance (D5), the distance (D*) covered by said swimmer (2) during said apnea sequence. Method (9) according to claim 5, characterized in that a total distance (Dt) covered by said swimmer (2) in said pool (3) between a starting point (PO) and the exit point (P2) is equal to the distance (D*) covered by said swimmer (2) during said apnea sequence added to a first distance (Dl) covered by said swimmer (2) on the surface of the water of said pool (3) between said starting point (PO) and said entry point (PI), said first distance (Dl) being calculated (962) from said positioning data.

7. System (1) for implementing the method (9) for determining the distance covered by a swimmer (2) during an apnea sequence in a pool (3) according to any one of claims 1 to 6, said pool (3) comprising two edges (31) spaced apart by a length (D) and said system (1) comprising: - at least one transmitter-receiver beacon (11), each beacon (11) being arranged at one of said two edges (31) of said basin (3); - a transmitter-receiver box (12) worn by said swimmer (2), said box (12) comprising an accelerometer type sensor; - a computing unit (10) adapted and configured for: - obtaining positioning data of said swimmer (2) when he is on the surface of the water of said pool (3), said positioning data coming from said at least one beacon (11) and / or said box (12); - obtaining movement data of said swimmer (2) when swimming under the surface of the water of said pool (3), said movement data coming at least from said accelerometer; - counting the number of turns made by said swimmer (2) while leaning against said edges (31) of said pool (3) from said movement data; and - determining the distance covered by said swimmer (2) during said apnea sequence in said pool (3) by combining said positioning data and said number of turns counted.

8. A computer program product characterized in that it comprises instructions for implementing, by a calculation unit (10), the method according to any one of claims 1 to 6, when said program is executed by a processor of the calculation unit (10). 20

9. A storage medium characterized in that it stores a computer program comprising instructions for implementing, by a computing unit (10), the method according to any one of claims 1 to 6, when said program is executed by a processor of the computing unit (10).

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