CODAS+UHDAS Documentation

This web site contains instructions for CODAS processing of ship-mounted ADCP data, and for operating the UHDAS system for acquiring those data.

An ADCP (Acoustic Doppler Current Profiler) is a device that uses the Doppler frequency shift of an acoustic ping to infer water velocity. A good source of background information about ADCPs can be downloaded from the long-time manufacturer of these instruments, Teledyne RDI. (For additional documents from RDI, see their support page.)

CODAS (Common Ocean Data Access System) is software built around a database originally developed by Ramon Cabrera in the late 1980’s as a portable, self-describing format for oceanographic data, motivated by the advent of ship-mounted ADCPs.

CODAS processing refers to the ADCP data processing software and procedures that have evolved over more than 30 years, and that still use the CODAS format. The processing steps have become increasingly automated, but human judgement is still required for the final product. The software is highly flexible in allowing manual configuration and execution of individual steps, as needed.

UHDAS (University of Hawaii Data Acquisition System) acquires data from RDI ADCPs and ancillary sensors (eg. gps, gyrocompass, gps and inertial attitude sensors…) and uses CODAS processing to incrementally build a dataset of averaged, edited ocean velocities for each ADCP and ping type specified. Processed data and plots are served on the shipboard network, and daily status summaries are emailed to those responsible for monitoring the system.


UHDAS is not a program, but a complex set of codes and system configurations. Setting up a new UHDAS installation requires Linux system administation skills, an understanding of UHDAS, and detailed knowledge of the particular suite of instruments and network environment on the ship. We are working to make the installation process easier and more automated, but at present it is not sufficiently documented to be done without specific training.

VmDAS is the software provided by Teledyne RDI for data acquisition on the Windows operating system. CODAS is capable of post-processing data acquired by VmDAS.

Additional background

An overview of shipboard ADCP systems was written for the GO_SHIP Repeat Hydrography Manual. For convenience, an html version of the shipboard ADCP contribution is included here. A brief introduction to UHDAS is given in an article in the magazine of The Oceanography Society. Here is a comparison of a 75-kHz Ocean Surveyor and 150-kHz Narrow Band.

Data Archiving

We strongly encourage the submission of final datasets to the official NODC archive for processed shipboard ADCP data, the Joint Archive for Shipboard ADCP. This collection of science-ready data is a valuable resource for future science. The work that goes into collection and processing the ADCP data can be leveraged to greater effect if the data are submitted.

This Documentation

CODAS documentation has accumulated over the years as acquisition programs, instruments, and processing programs have changed. Some of the old (but highly detailed) documentation contains references that are obsolete, but still relevant to old data sets; and many of the problems described in the old documentation still occur.

UHDAS+CODAS Documentation is evolving, as we gradually include more of it under the unifying framework facilitated by Sphinx. The full documentation is available at various entry points:

Contact for help.