Origin produces acoustic data in three different file formats: PD0, A-gram, and B-gram. Each format is a binary file format that is not human-readable.

What is PD0?

We have a separate FAQ giving more detail on PD0 (which can be found here), but essentially, this is a binary, industry-standard data format that describes the velocity profile measured by the ADCP as a function of depth, along with other parameters such as backscatter intensity, derived metrics, and metadata.

What is A-gram?

A-grams are a binary format proprietary to Sonardyne ADCPs. Each A-gram contains water velocity data sampled along the slant range of a single beam, along with other parameters (such as backscatter intensity), derived metrics, and metadata. One A-gram contains information pertaining to one beam. Thus, for a single ping, Origin 600 will produce five A-grams, one for each beam.

• A-gram water velocities are always logged in beam frame
• Origin logs A-gram to disk if requested within the mission configuration
• A-gram can provide up to factor 40 improvement in spatial fidelity compared to PD0 format velocity profiles
• All A-gram files are identified by a ‘.agram’ extension

What is B-gram?

B-grams are a binary format proprietary to Sonardyne ADCPs. Each B-gram contains raw acoustic data sampled along the slant range of a single beam, along with metadata. One B-gram contains information pertaining to one beam. Thus, for a single ping, Origin 600 will produce five B-grams, one for each beam.

• Origin logs B-gram to disk if requested within the mission configuration
• B-gram can provide up to factor 40 improvement in spatial fidelity compared to PD0 format files
• All B-gram files are identified by a ‘.bgram’ extension

How do A-gram and B-gram differ from PD0?

Like PD0, A- and B-gram hold common metadata. Formats differ by the extent to which data has been processed. It is possible to transform between the different data formats, but only in the order described below. It is not possible to convert from PD0 data to A-gram or B-gram, nor is it possible to convert from an A-gram to a B-gram.

When Origin pings and captures data, in the first processing step B-gram data is stored in memory. Each B-gram contains raw samples of the backscattered sound waves received by one beam. In the second processing step, the data content of a B-gram is processed to form the data content of an A-gram corresponding to that same beam. In the final processing step, once A-grams have been computed for all beams for that ping, they are binned into depth cells to produce one PD ‘ensemble’.