Method of compressing beamformed sonar data
Beamformed sonar data is compressed before communicating the data to a storage step or to a further processing step. At lease some of the beams of the compressed beamformed data have values for at least two different ranges.
1. A method, comprising:
a) insonifying a volume of fluid with a series of sonar pings, wherein the volume of fluid contains one or more objects;
b) receiving sonar signals reflected from the one or more objects, wherein the sonar signals are received by a large array of hydrophones located in the volume of fluid, and wherein the large array of hydrophones produces a set of raw data points for each sonar ping, wherein the set of raw data points comprises electrical signals which measure the phase and the intensity versus time of the sonar signal received by each of the large array of hydrophones for each ping; then
c) communicating the set of raw data points for each ping for further processing; then
d) beamforming the raw data points to produce values associated with sonar reflections from the one or more objects, wherein the values are associated with a large plurality of beams defined in a coordinate system having origin near the center of the large array of hydrophones, wherein each beam is defined a set of adjacent voxels in a volume of space radiating outwardly from the origin, and wherein each beam has a cross sectional area which increases with range from the origin; and then
e) compressing the beamformed data for at least one of the series of pings, wherein values are assigned are to two or more voxels in at least one or more separate beams, wherein the two or more voxels have different ranges from the origin; and then
f) communicating the compressed beamformed data for further processing.
2. The method of claim 1 , wherein the large array of hydrophones is arrayed as a two dimensional planar array having K by L elements, where both K and L are integers greater than 24.
3. The method of claim 2 , wherein the coordinate system is a spherical polar coordinate system, and wherein the large plurality of beams are non overlapping beams, and wherein the communicated beamformed data is compressed by comparing voxels with neighboring voxiles in each beam and/or in neighboring beams.
4. The method of claim 3 , wherein the large plurality of beams are non overlapping beams, and wherein the beamformed data is compressed by comparing voxels with neighboring voxiles in neighboring slices.
5. The method of claim 2 , wherein the coordinate system is a spherical coordinate system, and wherein the large plurality of beams are non overlapping beams, and wherein the beamformed data is compressed by comparing voxels with neighboring voxels from preceding and/or succeeding pings in the series of pings.
6. A method, comprising:
a) insonifying a volume of fluid with a series of sonar pings, wherein the volume of fluid contains one or more objects; then
b) receiving sonar signals reflected from the one or more objects, wherein the sonar signals are received by a large K by L array of hydrophones located in the volume of fluid, and wherein each of the large array of hydrophones produces a set S k l n of raw data points for each of a number N of slices for each sonar ping, wherein each set S k l n , (wherein k runs from 1 to L, l runs from 1 to L, and n runs from 1 to N), comprises electrical signals which measure the phase and the intensity versus time of the sonar signal received by each of the large array of hydrophones; then
c) compressing the raw data for each ping by comparing the raw data from each hydrophone with raw data from neighboring hydrophones and/or raw data from preceding and following slices;
d) beamforming the sets of compressed raw data points produce values associated with sonar reflections from the one or more objects, wherein the values are associated with a large plurality of beams defined in a coordinate system having origin near the center of the large array of hydrophones, wherein each beam is defined a set of adjacent voxels in a volume of space radiating outwardly from the origin, and wherein each beam has a cross sectional area which increases with range from the origin; and then
e) compressing the beamformed data for at least one of the series of pings, wherein values are assigned are to two or more voxels in at least one or more separate beams, wherein the two or more voxels have different ranges from the origin; and then
f) communicating the compressed beamformed data for further processing.
7. The method of claim 6 , wherein;
in step c) the raw data is compressed by comparing data for each hydrophone with data from neighboring hydrophones in at least one slice of each ping.
8. The method of claim 6 , wherein;
in step c) the raw data is compressed by comparing data for each hydrophone with data from neighboring slices for hydrophones at least some slices of each ping.
9. The method of claim 6 , wherein;
in step c) the raw data is compressed by comparing data for each hydrophone with data from neighboring hydrophones from preceding and subsequent pings in the series of pings.