Dive computer-integrated navigation system

Abstract

An underwater navigation system comprising: a buoy configured to be anchored underwater or suspended underwater from a boat, the buoy being configured to transmit a signal; and a dive computer configured to be worn by a diver, the dive computer configured to receive the signal and further configured to display a distance and direction to the buoy based on the received signal.

Description

FIELD OF THE INVENTION

[0001] The present invention relates generally to a navigation device and more particularly to an underwater navigation device. BACKGROUND OF THE INVENTION

[0002] For scuba divers, finding their way back to the dive boat after an extended stay underwater can be very difficult. Navigation underwater is challenging due to limited visibility and the lack of a clear visual reference. Traditionally, divers use a compass to determine direction and fin-stroke cycles to measure distance. Water movement, buoyancy adjustment, and the aforementioned lack of a visual reference can cause the diver to deviate from a direct path, making distance measurements highly inaccurate. Furthermore, when multiple dive boats are in close proximity, it can be difficult to locate the boat from which the diver embarked.

[0003] Some inertial navigation systems improve traditional track navigation by automating compass heading and tilt measurements. However, with longer dive times, drift leads to increasing position errors. High deviations from slow motion sensors (acceleration) can be improved by using current sensors, but since water constantly flows at variable speeds and directions, this solution only works if it is recalibrated frequently.

[0004] Underwater navigation systems that use triangulation receive a signal from multiple transmitters, which can be permanently installed or use a GPS-based position on the surface. Such systems can accurately determine the current location, and the path traveled can be stored. The system requires several transmitters, constant underwater communication between the transmitters and the receiver, and a lot of computing power. As a result, these systems tend to consume a lot of power. Ultimately, the cost and complexity of the system make it generally unsuitable for recreational diving. In addition, triangulation systems require the receiver to be placed in a shadow-free location, such as on the diver's back, and from there, the signal must be relayed somehow to the diver's wrist device or heads-up display. U.S. Patent No. 9,225,435 and U.S. Patent Publication No.2009 / 0213697 disclose related underwater navigation systems, and the entire teachings and disclosures of this patent and patent publication are incorporated herein by reference.

[0005] In addition, several other devices have been developed for underwater communication or for determining the distance and bearing of underwater objects. In particular, the following U.S. patents disclose devices for potential use in underwater navigation: U.S. 4,563,758, issued to C.J. Paternostro; U.S. 4,604,733, issued to B.F. Brown, et al.; U.S. 5,185,605, issued to J.W. Roberts, Jr., et al.; and U.S. 5,331,602, issued to C.B. McLaren, the entire teachings and disclosures of which are incorporated herein by reference.

[0006] Embodiments of the present invention provide an improved means for determining the distance and direction from a diver to a submersible. These and other advantages of the invention, as well as additional inventive features, will be apparent from the following description of the invention. BRIEF SUMMARY OF THE INVENTION

[0007] In one aspect, embodiments of the invention provide an underwater navigation system including a buoy configured to be anchored underwater or suspended underwater from a boat. The buoy is configured to transmit a signal. A dive computer is configured to be worn by a diver and also configured to receive the signal. The dive computer is further configured to display the distance and direction to the buoy based on the received signal.

[0008] In a particular embodiment, the signal is an ultrasonic signal. The ultrasonic signal may contain a unique address to identify the buoy transmitting the signal. Furthermore, the ultrasonic signal may contain two or more bits with a time delay between consecutive bits.

[0009] In certain embodiments, the buoy includes a sonar transmitter and an antenna element. In other embodiments, the buoy further includes a buoy microcontroller, a buoy reference clock, and a buoy Bluetooth communication module. The buoy may also include a power source, an LED light, and a water contact. In a particular embodiment, the dive computer includes a sonar receiver and a receiver antenna element. The dive computer may further include a dive computer microcontroller, a dive computer reference clock, and a dive computer Bluetooth communication module. In another embodiment, the dive computer further includes a user interface, a display, and an alarm. The alarm may be configured to provide haptic feedback.

[0010] In some embodiments, the dive computer includes one or more sensors. These one or more sensors may include a magnetic field sensor and a pressure sensor. Furthermore, the one or more sensors may include an inclination sensor and a water contact sensor. In a particular embodiment, the dive computer includes a microcontroller and an electric compass, and the microcontroller is configured to use data from the electric compass to determine a direction from the dive computer to the buoy.

[0011] In another embodiment, the dive computer includes a microcontroller and a tilt sensor, and the microcontroller is configured to use data from the tilt sensor to compensate for a tilt angle between the buoy and the dive computer. In more specific embodiments, the buoy has an upper end and a lower end, and the buoy includes an anchor point at both the upper and lower ends, the anchor points providing a means of attachment to the buoy. Additionally, the buoy may include an LED light configured to flash in one or more different patterns, each pattern indicating a different state of the buoy. Further, the buoy may be configured to repeatedly transmit the signal at periodic intervals.

[0012] Embodiments of the dive computer include a microcontroller configured to compare the strength and direction of a just received first signal with the strength and direction of a previously received second signal.

[0013] In particular embodiments of the invention, the buoy comprises a first microcontroller and a first reference clock, and the dive computer comprises a second microcontroller and a second reference clock, and the first and second microcontrollers are configured to synchronize the first reference clock with the second reference clock. In some embodiments, at least one of the first and second reference clocks is an Owen clock.

[0014] Furthermore, the first and second microcontrollers may be configured to synchronize the first and second reference clocks by transmitting a plurality of ultrasonic signals from the buoy to the dive computer. In a more specific embodiment, the first and second microcontrollers are configured to synchronize the first and second reference clocks by repeating an ultrasonic signal multiple times and averaging the detected times of the repeated ultrasonic signals.

[0015] In certain embodiments, the minimum number of ultrasonic signals required to synchronize the first and second reference clocks is determined by the precision to be achieved by the dive computer. Alternatively, the first and second microcontrollers may be configured to synchronize the first and second reference clocks by transmitting a plurality of radio waves from the buoy to the dive computer using the Bluetooth communication protocol.

[0016] In another embodiment, the dive computer includes a first antenna oriented in a first direction and a second antenna oriented in a second direction different from the first direction, wherein the dive computer is configured to determine the direction to the buoy based on the relative strengths of the signals received from the first and second antennas. The dive computer may further include a microcontroller and a receiver antenna element, wherein the microcontroller is configured to store an antenna beam pattern of the receiver antenna element and is further configured to determine a direction and an inclination angle between the buoy and the dive computer based on the stored antenna beam pattern and a strength of a signal received from the buoy.

[0017] Further aspects, objects and advantages of the invention will become more apparent from the following detailed description taken in conjunction with the accompanying drawings. BRIEF DESCRIPTION OF THE DRAWINGS

[0018] The accompanying drawings, which are incorporated in and constitute a part of the specification, illustrate various aspects of the present invention and, together with the description, serve to explain the principles of the invention. In the drawings: is Fig. 1 is a plan view of a buoy used in an underwater navigation system according to an embodiment of the invention; is Fig. Figure 2 is a schematic block diagram showing the elements of the buoy according to an embodiment of the invention; is Fig. 3 is a perspective view of the dive computer used in an underwater navigation system according to an embodiment of the invention; is Fig. 4 is a schematic block diagram showing the elements of the dive computer according to an embodiment of the invention; is Fig. 5A is a schematic diagram of a first exemplary ultrasound array with a 5-bit address according to an embodiment of the invention; is Fig. 5B is a schematic diagram of a second exemplary ultrasound array having a 5-bit address according to an embodiment of the invention; is Fig. Figure 6 is a schematic block diagram illustrating the synchronization or coupling of the sonar drive on the buoy with the sonar receiver on the dive computer and how this may be used to calculate distance in the water according to one embodiment of the invention; is Fig. 7 is a schematic block diagram illustrating how ultrasonic packets are received by a dive computer having an electric compass according to an embodiment of the invention; is Fig. Figure 8 is a schematic block diagram showing how the dive computer antenna receives the signal transmitted by the buoy according to an embodiment of the invention; is Fig. 9 is another schematic block diagram illustrating how ultrasonic packets are received by a dive computer having a tilt sensor according to an embodiment of the invention; and is Fig. 10 is a graphical representation of an exemplary polar diagram of an antenna beam pattern for the antenna element of the dive computer according to an embodiment of the invention.

[0019] While the invention will be described in connection with certain preferred embodiments, it is not intended to be limited to those embodiments. Rather, the intention is to cover all alternatives, modifications, and equivalents included within the spirit and scope of the invention as defined by the appended claims. DETAILED DESCRIPTION OF THE INVENTION

[0020] In a particular embodiment of the invention, the underwater navigation system comprises two units: a buoy 100 and a dive computer 200 with integrated receiver. Fig. 1 is a plan view of buoy 100, and Fig. Figure 2 is a schematic block diagram showing the elements of the buoy 100. Fig. 3 is a perspective view of the dive computer 200, and Fig. Figure 4 is a schematic block diagram showing the elements of dive computer 200. Buoy 100 marks the location to which the diver wishes to navigate. In particular embodiments, buoy 100 has a main body or housing 102 that is waterproof. The illustrated embodiment of buoy 100 also includes a power source 104 (disposable or rechargeable), an on / off switch 106, a microcontroller 108, a clock source 110, an ultrasonic transmitter 112, a Bluetooth communication module 114, an ultrasonic antenna 116, an optional LED flash 120, and an optional water contact 118.

[0021] In some embodiments, the water contact 118 is configured to detect the presence of water. In the case of the buoy 100, the water contact 118 would know when it is underwater (e.g., close Bluetooth communication doesn't work underwater), or, if removed from the water, the water contact 118 could automatically either turn off, place into a power-saving mode, or even dim the flashlight, which might otherwise be very bright.

[0022] In certain embodiments of the buoy 100, the ultrasonic antenna 116 is an omnidirectional ultrasonic antenna in which the beam pattern is optimized so that the antenna gain is the same on all sides and in all directions (i.e., for 360 degrees) around the antenna 116. The main signal may be directed downward from the antenna 116. The buoy 100 may be suspended from the side of the boat, anchored to a floating object, or anchored in a lake or riverbed. In certain embodiments, the buoy 100 has at least two anchoring points 122 (one at each longitudinal end of the buoy 100) so that the buoy 100 can be anchored with the antenna 116 facing either downward or upward.

[0023] In certain embodiments, the buoy 100 transmits signals in the form of ultrasonic packets. Typically, each ultrasonic packet contains at least one unique address to identify the buoy 100, since there may be multiple buoys 100 at a dive site. Using the unique address, the diver can select the desired buoy 100 from among the many buoys 100 that may be located at a particular dive site.

[0024] Each ultrasound packet contains a series of bits with a specific time interval or time delay between consecutive bits. In some embodiments, the time delay between packet address bits, as well as the value of the packet address bits, can be changed depending on the dive site. Fig. 5A and Fig. 5B show schematic representations of two example packets, each with a 5-bit address. As can be seen, the two packets have the same encoding, but the packet in Fig. 5B has a longer delay between bits than the delay in Fig. 5A. One skilled in the art would recognize that the buoy could be configured to transmit ultrasonic packets of fewer or more than five bits.

[0025] Due to reflections and multiple signal paths through the water, ultrasonic packets with a larger time delay between packet address bits are easier to detect in certain environments, such as when there is a flat rocky bottom that reflects ultrasonic waves well. In embodiments of the invention, the shape and encoding of the ultrasonic packets can be adjusted by the dive computer 200 via the Bluetooth communication protocol.

[0026] The package from Fig. 5A, for example, may be better suited for a deep water dive site, while the package of Fig. 5B may be better suited for shallow water dive sites. Other dive site characteristics where some type of signal pattern, as in Fig. 5A, can work better than the other in Fig. 5B, are near, among others, a reef wall, a drop-off, a sloping bottom, a kelp forest, etc. In a particular embodiment of the invention, the ultrasound packets are repeated with preset time delays between successive bits, and these time delays are defined by the system clock 110. The time delay can be set so that, in the area of ​​the buoy 100 (or the ambient reflections), the current ultrasound packet and the next ultrasound packet after the current ultrasound packet do not collide or interfere with each other.

[0027] In a particular embodiment, the buoy 100 has an electrical system that includes a precise clock 110. In such embodiments, the clock 110 may be a temperature-compensated type to increase accuracy, since the water temperature is typically much lower than the air temperature. In more specific embodiments, it may also be a more precise Owen clock 110, where the temperature of the clock is kept constant and independent of the environment. An Owen clock 110 is maintained at a stable temperature, unlike a clock where the user attempts to compensate for a changing temperature. Typically, the selected stable temperature for the Owen clock 110 is chosen above the operating temperature, since it is generally easier to heat the clock 110 than to cool it.

[0028] The buoy 100 may have a display or haptic feedback. However, these can be eliminated by using a wireless communication protocol, such as Bluetooth, which operates in the air when the buoy 100 is not submerged. Bluetooth communication can therefore replace any dynamic buttons that might be vulnerable to water leakage. In its simplest form, the buoy 100 has only the on / off switch 106. When the buoy 100 is powered only via switch 106, Bluetooth mode is active for a specific period of time, creating a time window during which the buoy 100 can be programmed. After a predetermined period of time, Bluetooth mode is deactivated, and the buoy 100 operates in underwater mode, transmitting the aforementioned ultrasonic packets for underwater navigation. Bluetooth mode can also be deactivated using a water sensor contact.

[0029] The buoy 100 may also include a visual navigation aid for close-range finding. This can be achieved by using multiple colors on the buoy housing 102. These colors are typically chosen to provide high contrast with water and sunlight. For example, using a housing color combination of black and yellow offers several advantages. Black provides high contrast in sunny areas with high light intensity, while yellow is highly visible on cloudy days or in the evening / morning.

[0030] For navigation at night or in low-light conditions, the buoy housing 102 or a portion of the buoy housing 102 may be made of a self-luminous material that glows for a period of time after exposure to light. Additionally, the buoy housing 102 may include a flashing or constant LED 120. In one particular embodiment, multiple LEDs 120 are arranged around the housing 102 so that the light is visible from any direction. Alternatively, the housing 102 could include an LED 120 and a plurality of reflectors that direct the light from the LED 120 360 degrees around the entire housing 102. The LED 120 may also be used as a diagnostic tool, allowing the user to determine if the buoy 100 is functioning properly, i.e., constant intermittent flashing, or to indicate battery life, e.g.,brief flashing to indicate low battery power, or no flashing at all to indicate that some type of error exists with the buoy 100 or with the self-diagnostic routine of the buoy 100 initiated during commissioning. Thus, the LED light 120 can be configured to indicate a condition of the buoy 100 by flashing in one or more different predefined patterns, each pattern indicating a different condition of the buoy 100.

[0031] In an alternative embodiment, the buoy housing 102 includes a combination of the aforementioned features, wherein the self-luminous material is exposed to light pulses from the LED 120 and thereafter continuously illuminates at a lower intensity than that of the light pulses.

[0032] Regarding the dive computer 200 with integrated receiver, in certain embodiments, the dive computer 200 is worn by the diver, and the integrated navigation receiver indicates the direction and distance to the buoy 100. The integration of the navigation receiver into the dive computer 200 expands the capabilities of the system in several ways, allowing the diver to navigate underwater without having to carry two different instruments.

[0033] The housing 202 of the dive computer is waterproof and houses several elements. Inside the housing 202 are a power source 204, a user interface 206, a display 208, a microcontroller 210, an electronic memory, a haptic feedback alarm 212, such as a vibrating alarm, a precision clock 214, a Bluetooth communication module 216, an ultrasonic receiver 218, and an ultrasonic antenna element 220. The dive computer 200 also contains one or more sensors 222, which may include, among others, a pressure sensor, direction sensors such as an electric compass, one or more tilt sensors or acceleration sensors, and a water contact.

[0034] In a particular embodiment, the dive computer 200 is configured to use the microcontroller 210 and the Bluetooth communication module 216 to configure the buoy 100. This configuration allows, for example, the ultrasonic packet address to be selected, the ultrasonic packet interval or time delay to be set, the flashing LED 120 to be activated or dimmed, and the battery status or remaining operating time of the buoy 100 to be displayed.

[0035] In certain embodiments, the dive computer 200 is synchronized or paired with the buoy 100 prior to the dive or at the beginning of the dive. Fig. Figure 6 is a schematic block diagram illustrating the synchronization or pairing of the sonar drive 112 on the buoy 100 with the sonar receiver 218 on the dive computer 200 according to one embodiment of the invention. If pairing occurs pre-dive, it may be accomplished via Bluetooth or by bringing the ultrasonic receiver antenna 220 of the dive computer 200 into proximity with the antenna 116 of the buoy 100. If pairing occurs via ultrasonic signals, multiple ultrasonic packets and averaging are used to achieve precise synchronization between the reference clock 110 of the buoy 100 and the reference clock 214 of the dive computer 200. Averaging is used because the acquisition of the ultrasonic pulses occurs at a relatively low frequency and therefore typically has some inaccuracy.To define a specific fixed signal level from which the correct time can be determined, the signal is repeated several times and averaged between the acquired times to eliminate interference such as noise, etc. This allows for more accurate synchronization between the transmitted and received signals.

[0036] The minimum number of received ultrasonic packets required to accurately indicate the position of buoy 100 is determined by the accuracy required by dive computer 200. In addition, ultrasonic pairing typically requires a minimum signal level for valid packets.

[0037] If the diver is already in the water (i.e., Bluetooth is not working) and wants to pair their dive computer 200 with the buoy 100, the dive computer 200 must be physically close to the buoy 100 due to the minimum signal level of the ultrasonic packets. In one specific embodiment, the pairing is valid for a specific period of time, also called the synchronization period, when the difference between the transmitter clock and the receiver clock is small enough to allow accurate distance measurement. After the synchronization period has elapsed, the buoy 100 and the dive computer 200 return to their normal operating mode.

[0038] Pairing can be a specific mode for the Buoy 100 and the Dive Computer 200, or just for the Dive Computer 200. After the synchronization period has elapsed, the Dive Computer 200 enters a "timeout" mode. In this case, pairing between the Buoy 100 and the Dive Computer 200 must be performed again to synchronize the reference clocks 110 and 214 of the two devices. If the Dive Computer 200 is submerged without a valid pairing, the Dive Computer 200 can be programmed to sound an alarm to warn the diver so that pairing can be performed at the beginning of the dive. During a long dive, the Dive Computer 200 will function as usual, even if it does not enter Timeout mode during the dive. However, during a very long dive, the timeout may occur immediately upon surfacing.However, after surfacing, the distance calculation is no longer so important, since the diver should be able to see the boat or buoy 100.

[0039] For example, one scenario might involve a three-hour synchronization between buoy 100 and dive computer 200, while the dive has just begun 2.5 hours into the three-hour synchronization period, and the expected dive time is one hour. The synchronization period would end during the dive, causing dive computer 200 to enter a time-override mode. Dive computer 200 would continue to display the distance and direction to buoy 100. However, time-override mode displays the time elapsed since the last synchronization of reference clocks 110 and 214. As the time between synchronizations increases, the inaccuracy of the dive computer's distance calculation may also increase.

[0040] When the dive computer 200 and the buoy 100 are synchronized, the dive computer 200 is configured to calculate the distance between the two devices. The distance is based on the time the ultrasound packet was transmitted, the time the ultrasound packet was received, and the speed of sound in the water. The dive computer 200 can use the parameters detected by one or more sensors 222, such as temperature or salinity, to accurately determine the speed of sound in the water.

[0041] The direction of buoy 100 is determined by the strength of the received packet signal. As in Fig. As shown in Figure 7 and described below, when comparing two different ultrasonic packet signals, the stronger packet signal is received when the antenna 220 of the dive computer 200 is pointed directly at the buoy 100 or has a smaller angular deflection away from the buoy 100. Since the strength of the received packet signal is highest when the dive computer 200 is directly in front of the buoy, the highest degree of accuracy is achieved at this point. When a diver wishes to navigate to the buoy 100, they will typically hold the dive computer 200 with the front of the dive computer 200 facing forward.

[0042] In cases where two differently angled antennas and receivers are used, the signal strength of both can be compared. Buoy 100 is obviously more in the direction of the stronger signal. This property is in Fig. 8, a schematic block diagram showing how the dive computer 200 receives the signal transmitted by the buoy 100. In the embodiment of Fig. 8, the dive computer 200 has two separate antennas: a first antenna 270 oriented in a first direction, and a second antenna 272 oriented in a second direction different from the first direction. The first antenna 270 has a first antenna beam pattern 274, and the second antenna 272 has a second antenna beam pattern 276. The direction to the buoy 100 can be determined based on the relative strength of the signals received by the first and second antennas 270, 272.

[0043] Fig. Figure 7 is a schematic block diagram showing how ultrasonic packets are received by dive computer 200, which includes an integrated electric compass 224 according to one embodiment of the invention. As shown in Fig. 7, the antenna 220 has a horizontal beam pattern 226. Due to the shape of the horizontal beam pattern 226, the packet signal 228 transmitted by the buoy 100 is best received by the dive computer antenna 220 when it is in position C (i.e., the dive computer is facing west when the top of the side is facing north). Reception of packet signals is weaker in positions B and D, and no signal is received at all in position E. The integrated electric compass 224 in the dive computer 200 enables the device 200 to compare previously received packet signals with current packet signals, allowing the dive computer 200 to make an instantaneous heading correction.

[0044] When the packet signal is received, the dive computer 200, which has the integrated electric compass 224, stores the compass reading at that time. The compass reading can be compared with previous compass readings, and the area where the buoy 100 is located can be narrowed down. If the received ultrasound signal shows that the buoy 100 is farther away and the dive computer 200 can determine the diver's maximum speed in the water, the valid direction to the buoy 100 can be stored in the electric compass 224 for a longer period of time. At shorter distances, the compass direction is valid for a shorter period of time.

[0045] Fig. Figure 9 is another schematic block diagram showing how ultrasonic packets are received by the dive computer 200 incorporating the tilt sensor 222 according to an embodiment of the invention. As shown in Fig. 9, the antenna 220 has a vertical beam pattern 230. Due to the shape of the vertical beam pattern 230, the packet signal 228 transmitted by the buoy 100 is best received by the dive computer antenna 220 when it is in position C. However, using the data from the tilt sensor 222, the microcontroller 210 of the dive computer 200 is configured to determine the deviation of the packet signal 228 from horizontal and to compensate for any tilt angle between the transmission of the packet signal 228 and the antenna 220 of the dive computer 200. In this way, the dive computer 200 is able to compensate for the difference in depth, or tilt angle, between the buoy 100 and the dive computer 200, where the tilt angle is determined by the magnitude of the difference in depth.

[0046] In another embodiment, a pressure sensor 222 provides the current depth, and if the buoy 100 is exposed near the surface, the tilt direction of the buoy 100 can be estimated, or if it is anchored, the horizontal direction to the anchoring point of the buoy 100 can be estimated.

[0047] To conserve power on the dive computer 200, the navigation receiver 218 can be placed in a low-power sleep mode. When the diver wishes to navigate to the buoy 100, this can be done, for example, by pressing a button on the user interface 206 to activate navigation. In a particular embodiment, the ultrasonic receiver 218 is placed in high-gain mode when navigation is initiated. When an ultrasonic packet is received by the dive computer 200, a distance between the buoy 100 and the dive computer 200 can be calculated.

[0048] Because the ultrasonic packets are transmitted with a known interval or time delay between consecutive bits, the receiver 218 can be turned off after the dive computer 200 receives an ultrasonic packet to conserve power until the expected time window for the next ultrasonic packet. When the dive computer 200 is in close proximity to the buoy 100, it can automatically switch the ultrasonic receiver 218 to low-gain mode to ensure optimal directional accuracy.

[0049] In a typical embodiment, the dive computer 200 is worn on the diver's wrist. The relatively fixed position on the diver's wrist during use of the navigation system contributes to stabilizing the ultrasonic receiver 218 and helps keep the dive computer 200 horizontal. Furthermore, the three-dimensional acceleration sensors 222 (also referred to as "tilt sensors") of the dive computer 200 can detect whether the receiver antenna 220 is tilted, and this can be compensated for if the three-dimensional pattern of the receiver antenna 220 is known.

[0050] Fig. 10 is a graphical representation of an exemplary polar diagram of an antenna beam pattern 300 for the antenna element 220 of the dive computer 200. Since the antenna element 220 has a beam pattern (i.e., a gain) in each axis of rotation, the direction and angle of inclination to the buoy 100 can be determined based on the antenna beam pattern 300 and the corresponding gain in each of the three dimensions. As can be seen from Fig. 10, the antenna beam pattern 300 has a much higher gain in the 90 degree direction (top) and smaller roll gains in the zero degree and 180 degree directions in the illustrated rotation axis.

[0051] If the distance measurement between the buoy 100 and the dive computer 200 is based on a common reference clock 110, 214, the navigation system can be constructed using unidirectional communication. The power consumption of the dive computer 200 can be minimized and its size optimized. The receiver 218 can be more efficiently coupled to the receiver antenna 220. Accordingly, if the buoy 100 only needs to transmit, it can be optimized for this purpose.

[0052] Magnetic sensors 222 in the dive computer 200 can be used to determine the direction of the received packet, and the strength of these signals can be stored in the electronic memory of the microcontroller 210. The strength and direction of the next received ultrasonic packet can be compared with that of the previous packet. The stronger of these two signals is likely from the dive computer 200, whose antenna 220 is more directly aligned with the buoy 100. The dive computer 200 can therefore calculate the angle from which the signal is coming. In addition, additional sensors 222 of the dive computer 200 are used to increase its directional accuracy. As explained above, the microcontroller 210 can use the data from the tilt sensor 222 to compensate for ultrasonic packets received when the antenna 220 is not level with the packet signal 228 transmitted by the buoy 100.

[0053] In a situation where a diver becomes lost and cannot visually determine the way back to the submersible, the diver can initiate a 360-degree search using the dive computer 200, which is a special mode programmed into the dive computer 200. This mode guides the diver through specific steps to determine the direction to the buoy 100. When the ultrasonic receiver 218 detects an ultrasonic pulse transmitted by the buoy 100, the dive computer 200 displays the sensed directions and the tilt deviation on the display. Although best results can be achieved when the dive computer 200 is held in the horizontal position, the dive computer 200 is also configured to compensate for a tilt angle between the buoy 100 and the dive computer 200. The dive computer 200 stores the packet strength and direction during the search.After completing the scan, the dive computer 200 identifies the strongest packet signal from multiple received packets, which likely came from the direction directly in front of the antenna 220 at the time of signal reception, thus indicating the direction to the buoy 100. Reflections in the case of multipath propagation of the signal can be eliminated because they are typically weaker than the direct path.

[0054] The above-described embodiments of the invention provide improved navigation capabilities compared to conventional underwater navigation systems. Unlike some conventional systems, the dive computer 200 does not require the diver to maintain the ultrasonic receiver 218 in a constant horizontal or level position to obtain accurate direction readings. The requirement to maintain the receiver unit in a level position can be difficult underwater because the diver is constantly moving, even when just hovering, without a fixed reference point.

[0055] All references, including publications, patent applications, and patents cited herein are hereby incorporated by reference to the same extent as if each reference were individually and expressly indicated to be incorporated by reference and reproduced herein in its entirety.

[0056] The use of the terms "a" and "an" and "the" and similar designations in connection with the description of the invention (particularly in connection with the following claims) is to be construed to include both the singular and the plural, unless otherwise stated herein or the context clearly contradicts it. The terms "comprising," "having," "including," and "containing" are to be construed as open-ended terms (i.e., in the sense of "including, but not limited to") unless otherwise stated. Reference to ranges of values ​​is merely a shorthand for each individual value falling within the range, unless otherwise stated herein, and each individual value is included in the description as if individually recited herein.All methods described herein may be performed in any suitable order, unless otherwise specified herein or the context clearly dictates otherwise. The use of examples or exemplary phrases (e.g., "how") is merely intended to better illustrate the invention and is not intended to limit its scope unless otherwise specified. No language in the specification should be construed to infer any unclaimed element as essential to practicing the invention.

[0057] Preferred embodiments of this invention are described herein, including the best mode known to the inventors for carrying out the invention. Variations of these preferred embodiments may become apparent to those skilled in the art upon reading the foregoing description. The inventors believe that those skilled in the art will appropriately employ such variations, and the inventors intend to practice the invention otherwise than as described herein. Accordingly, this invention includes all modifications and equivalents of the subject matter recited in the appended claims permitted by applicable law. Furthermore, any combination of the elements described above in all possible variations thereof is encompassed by the invention unless otherwise stated herein or clearly contradicted by context. QUOTES CONTAINED IN THE DESCRIPTION

[0000] This list of documents submitted by the applicant was generated automatically and is included solely for the convenience of the reader. This list is not part of the German patent or utility model application. The DPMA assumes no liability for any errors or omissions. Cited patent literature

[0000] US 4,563,758

[0005] US 4,604,733

[0005] US 5,185,605

[0005] US 5,331,602

[0005]

Claims

[1] An underwater navigation system comprising: a buoy configured to be anchored underwater or suspended underwater from a boat, the buoy being configured to transmit a signal; and a dive computer configured to be worn by a diver, the dive computer configured to receive the signal and further configured to display a distance and direction to the buoy based on the received signal. [2] The underwater navigation system according to claim 1, wherein the signal is an ultrasonic signal. [3] The underwater navigation system of claim 2, wherein the ultrasonic signal includes a unique address for identifying the buoy transmitting the signal, and / or wherein the ultrasonic signal comprises two or more bits with a time delay between consecutive bits. [4] The underwater navigation system according to claim 1, wherein the buoy includes a sonar transmitter and an antenna element. [5] The underwater navigation system of claim 4, wherein the buoy further includes a buoy microcontroller, a buoy reference clock, and a buoy Bluetooth communication module, and / or wherein the buoy further includes a power source, an LED light, and a water contact. [6] The underwater navigation system according to claim 1, wherein the dive computer includes a sonar receiver and a receiver antenna element. [7] The underwater navigation system of claim 6, wherein the dive computer further includes a dive computer microcontroller, a dive computer reference clock, and a dive computer Bluetooth communication module, and / or wherein the dive computer further includes a user interface, a display, and an alarm, the alarm optionally providing haptic feedback. [8] The underwater navigation system of claim 6, wherein the dive computer further includes one or more sensors. [9] The underwater navigation system of claim 8, wherein the one or more sensors include a magnetic field sensor and a pressure sensor and / or wherein the one or more sensors include an inclination sensor and a water contact. [10] The underwater navigation system according to claim 1, wherein at least one of the following statements is true: - the dive computer includes a microcontroller and an electric compass, and wherein the microcontroller is configured to use data from the electric compass to determine a direction from the dive computer to the buoy; - the dive computer includes a microcontroller and an inclination sensor, and wherein the microcontroller is configured to use data from the inclination sensor to compensate for an inclination angle between the buoy and the dive computer; - the buoy has an upper end and a lower end, and wherein the buoy includes an anchor point at both the upper and lower ends, the anchor points providing a means of attachment to the buoy; - the buoy has an LED light configured to flash in one or more different patterns, each pattern indicating a different state of the buoy; - the buoy is configured to repeatedly transmit the signal at periodic intervals, wherein the dive computer optionally comprises a microcontroller configured to compare the strength and direction of a just received first signal with the strength and direction of a previously received second signal. [11] The underwater navigation system of claim 1, wherein the buoy comprises a first microcontroller and a first reference clock, and the dive computer comprises a second microcontroller and a second reference clock, and wherein the first and second microcontrollers are configured to synchronize the first reference clock with the second reference clock. [12] The underwater navigation system of claim 11, wherein the first and second microcontrollers are configured to synchronize the first and second reference clocks by transmitting a plurality of ultrasonic signals from the buoy to the dive computer. [13] The underwater navigation system according to claim 12, wherein at least one of the following statements is true: - the minimum number of ultrasonic signals required to synchronise the first and second reference clocks is determined by the precision to be achieved by the dive computer; - the first and second microcontrollers are configured to synchronise the first and second reference clocks by either sending a plurality of ultrasonic signals from the buoy to the dive computer or by using the Bluetooth communication protocol to send signals from the buoy to the dive computer; - the first and second microcontrollers are configured to synchronize the first and second reference clocks by repeating an ultrasonic signal several times and averaging the detected times of the repeated ultrasonic signals. [14] The underwater navigation system of claim 11, wherein one of the first and second reference clocks is an Owen clock. [15] The underwater navigation system according to claim 1, wherein at least one of the following statements is true: - the dive computer has a first antenna oriented in a first direction and a second antenna oriented in a second direction different from the first direction, the dive computer being configured to determine the direction to the buoy based on the relative strengths of the signals received by the first and second antennas; - the dive computer includes a microcontroller and a receiver antenna element, wherein the microcontroller is configured to store an antenna beam pattern of the receiver antenna element and is further configured to determine a direction and an inclination angle between the buoy and the dive computer based on the stored antenna beam pattern and a strength of a signal received from the buoy.

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