Determining a position of a submersible vehicle within a body of water
Methods and apparatus determining a position of a submersible vehicle within a body of water are provided. A method comprises determining an initial position of the vehicle while the vehicle is at or near a water surface. The method further comprises coupling the vehicle and a base node to a weight and determining a position of the base node once the base node and vehicle have reached the floor of the body of water using acoustic modems of the vehicle and a surface vessel to aid in calculating the position as they descend, and acoustically transferring the at rest position on the seafloor from the vehicle to the node. The method further comprises decoupling the vehicle from the node and weight and determining a position of the vehicle based on the position of the base node and acoustic signals exchanged between acoustic modems of the vehicle and the base node.
1. A method of determining a position of a submersible vehicle within a body of water, comprising:
determining an initial position of the vehicle while the vehicle is at or near a surface of the body of water;
coupling the vehicle and a base node to a weight configured to descend the base node and the vehicle to a floor of the body of water;
determining a position of the base node once the base node and vehicle have reached the floor of the body of water, wherein determining a position of the base node comprises exchanging acoustic signals between a first acoustic modem of the vehicle and a second acoustic modem of a surface vessel;
decoupling the vehicle from the weight while the base node stays coupled to the weight;
and determining a position of the vehicle based on the position of the base node and acoustic signals exchanged between the first acoustic modem of the vehicle and a third acoustic modem of the base node.
2. The method of claim 1 , further comprising determining a position of the vehicle during descent by exchanging acoustic signals between the first acoustic modem of the vehicle and the second acoustic modem of the surface vessel.
3. The method of claim 2 , wherein determining a position of the vehicle during descent comprises:
determining a range between the vehicle and the surface vessel using an acoustic signal from the surface vessel;
measuring data regarding one or more properties of the body of water that affect the transmission of acoustic signals between the vehicle and the surface vessel using a sensor of the vehicle; and
adjusting the determined range based on the measured data regarding the one or more properties of the body of water that affect the transmission of the acoustic signals.
4. The method of claim 3 , wherein the sensor comprises a conductivity, temperature, and depth sensor and the data includes temperature, salinity, and pressure data of the water.
5. The method of claim 1 , wherein the initial position of the vehicle is determined using a positioning circuit of the vehicle.
6. The method of claim 5 , wherein the positioning circuit comprises a global positioning system.
7. The method of claim 1 , wherein determining a position of the vehicle comprises:
determining the position of the vehicle using an inertial navigation system; and
updating the position of the vehicle based on the position of the base node and the acoustic signals exchanged between the first acoustic modem of the vehicle and the third acoustic modem of the base node.
8. The method of claim 1 , wherein at least one of determining a position of the base node and determining a position of the vehicle comprises:
receiving an acoustic signal at a plurality of transducers of the vehicle;
determining a bearing and a range associated with the acoustic signal based on a difference in the phase and timing of the signal as it is received at each of the plurality of transducers; and
determining the respective position based on the bearing and the range.