Underwater Navigation System

From PDI

Preface

Navigation underwater for Scuba diving in most cases is still fairly primitive, using simple mechanical magnetic or a digital magnetic compass in conjunction with maps, water flow measurements, and kick stroke counts. GPS devices work very poorly as the signal will not penetrate adequately into water of any significant depth.

I propose a dramatic improvement in accuracy using common technology currently used in other environments today.

Claims

1. Basic device to determine distance and direction of motion underwater requiring the following:
   1. Time measurement.
   2. Magnetic compass reading (3 axes preferred).
   3. Acceleration and deceleration measurements (3 axes preferred).
   4. Capability to log the data or output from calculations derived from the sensor data.
   5. Means to download logged data.
2. Implementation of Time measurement is done through precision oscillator in conjunction with microprocessor.
3. Implementation of magnetic compass reading (via, 1,2, or 3 axes) magnetoresistive sensors or similar technologies that are sensitive to magnetic fields and can be converted to digital signals though any of the common analog to digital conversions methods.
4. Implementation of Acceleration and Deceleration (1,2, or 3 axes) using accelerometers. For cost and accuracy, MEMS accelerometers are preferred, which are accurate and low cost providing a choice of analog and digital outputs. Optionally Gyros can be used in a similar matter, but for this implementation we will focus on the use of accelerometers.
5. Optional entry of current location coordinates. This can be provided either by map or GPS, and entered either via entry device or automatically in order to provide new coordinates at end point. Optionally GPS could be integrated directly with the rest of the device.
6. Data can be downloaded from stored navigation information via serial methods, optical light transmission, or Radio Frequency: all methods commonly used today to move data from stored sources to secondary storage for display or further analysis.
7. Optionally device may display real time data using any of the various display methods: LCD technologies, showing compass, speed, distance, coordinates.
8. Optionally pressure sensor may be added to provide a secondary or backup indication of depth. Primary depth measurement would be from first location at surface, but this does not preclude from starting navigation start point from some underwater depth or location.
9. Optionally entry device may have a keypad or keyboard or incorporate speech recognition.
10. Firmware or software is written to take advantage of all sensor data input to determine the rate of movement and direction. This information is logged as way points, and also can be used to guide one to specific way points logged previously. Primary method of motion detection is rate of acceleration, time at the various acceleration in comparison to rate of deceleration, and time at deceleration in conjunction with compass bearing. This inertial navigation system using 3 axes will provide a fairly accurate reading of distance traveled from point "A" to "B". This can be improved and increased accuracy by a addition of other devices mentioned such as GPS, initial location, pressure measurements, or/and gyros. Application of Gyros can provide additional 3 axes of motion pitch, roll, and yaw, but typically this would not be needed in general navigation.