R2Sonic 2026, Operation Manual

Page: 221 / 254

Page 221 of 254
Version 6.3 Rev r012
Date 05-11-2022
15.9 Acoustic Image (AI) Data Format
// *** BEGIN PACKET: ACOUSTIC IMAGE (AI) DATA FORMAT 0 ***
// The acoustic image data contains real-time beamformer 8-bit magnitude data
// (beam amplitude) that has been scaled to 8-bits by a user-selected
// brightness value, and compressed in range by an adjustable amount to
// reduce network bandwidth and processing. The data is called "samples"
// before compression and "bins" after compression. For example, 7200 samples
// of beamformer data (M0_TotalSamples) may be compressed to 600 bins
// (M0_TotalBins). The number of beamformed data samples normally extends
// somewhat further than the user's range setting. The AIH0 sonar command
// sets an upper limit to the number of compressed output bins. It's not a
// precise compression factor, so the number of bins is usually somewhat less
// than the AIH0 value. The maximum data rate with no compression is about
// 17.5 megabytes per second (assuming 256 beams).
//
// When the operator enables acoustic image mode, each sonar ping outputs
// numerous 'AID0' packets containing: one H0 header section, one A1 beam
// angle section, and many M0 data sections. The section order may change in
// the future, so plan for that in your data acquisition.
//
// Each M0 section contains a subset of the ping data. Its header indicates
// its size position to help you assemble the full ping array.
//
// You may wish to detect missing M0 data sections (perhaps a lost UDP
// packet), and then fill the gap with zeros or perhaps data from the
// previous ping (to reduce visual disturbances), and then increment an error
// counter for network health monitoring purposes.
//
// The acoustic image data is basically in polar coordinates, so you may wish
// to geometrically warp it into the familiar wedge shape for display.
// Consider using OpenGL or Direct3D texture mapping.
u32 PacketName; // 'AID0'
u32 PacketSize; // [bytes] size of this entire packet
u32 DataStreamID; // reserved for future use
// section H0: header (only one per ping)
u16 H0_SectionName; // 'H0'
u16 H0_SectionSize; // [bytes] size of this entire section
u8 H0_ModelNumber[12]; // example "2024", unused chars are nulls
u8 H0_SerialNumber[12]; // example "100017", unused chars are nulls
u32 H0_TimeSeconds; // [seconds] ping time relative to 0000 hours 1-Jan-1970, integer part
u32 H0_TimeNanoseconds; // [nanoseconds] ping time relative to 0000 hours 1-Jan-1970, fraction part
u32 H0_PingNumber; // pings since power-up or reboot