UHDAS+CODAS Documentation

An ADCP (Acoustic Doppler Current Profiler) is a device made by Teledyne RD Instruments that uses the Doppler frequency shift of an acoustic ping to infer water velocity. It is a registered trade name. ADCPs are attached to moorings, lowered on CTD rosette packages, and mounted on ship hulls. This web site deals with shipboard ADCPs.

If you are unfamilar with how and ADCP works, please visit the Teledyne R.D.Instruments website and download the ADCP (BroadBand) Practical Primer. They will ask you to create an account, but there is no cost. This outlines the underlying concepts behind how an ADCP works.

A CODAS (Common Ocean Data Access System) database is a way to store and access oceanographic data. CODAS was developed in the late 1980’s as a portable, self-describing format for oceanographic data, with emphasis on processed ADCP data.

CODAS processing refers to the ADCP data processing software and procedures that were developed around the CODAS format. The processing steps have become increasingly automated, but human judgement is still required for the final product, and the software is highly flexible in allowing manual configuration and execution of individual steps.

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.


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”, on the other hand, is the software provided by TRDI for data acquisition that runs on Windows operating system (UHDAS runs on a Linux OS with no need of other software acquisition as VMDAS itself). CODAS is capable of post-processing data acquired by VmDAS (as ENR, LTA or STA) as will be described in the following pages in this documentation web site.


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. This article in The Oceanography Society provides an overview. Continued funding for UHDAS+CODAS support has been through the University of Hawaii Technical Services program, NSF award 1227720. Starting October 2014, support for UHDAS on the NOAA fleet has been funded by NA11NMF4320128.

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.


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:


The new graphical tools (for editing and viewing) require Python3. The old Python2 documentation still exists here

If you have any question, please email us and we’ll help you figure out the best way forward.

Contact uhdas@hawaii.edu for help.