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Analyzing and Visualizing Flows in Rivers and Lakes with MATLAB


ADCPs and VMT have increased the pace of studies that rely on flow data. Find out how these toolkits from MathWorks are revolutionizing the analysis and visualisation processes.



The evolution of VMT included adding more visualization tools for ADCP data. For example, researchers can compare flow velocity data at different depths and strata, map primary and secondary circulation patterns, and plot depth-averaged velocities on aerial maps (Figure 3).

Figure 3. Depth-averaged velocities plotted using VMT on an aerial view of the confluence of the Wabash and Embarras Rivers (Illinois) with ADCP-derived bathymetry.
Figure 3. Depth-averaged velocities plotted using VMT on an aerial view of the confluence of the Wabash and Embarras Rivers (Illinois) with ADCP-derived bathymetry.

The development of a graphical interface for VMT makes it easy for researchers to import data from ASCII files or MAT-files generated by ADCPs (Figure 4). Researchers can use this interface to load and process data files, create easy-to-understand 2D and 3D MATLAB plots of velocity data (Figure 5), export processed data and figures for further analysis and visualization, or access VMT-related data processing utilities that make data available to other programs such as Geographic Information Systems (GIS) and Google Earth®. With MATLAB Compiler™, VMT’s developers created a standalone executable version of the application that researchers can use without installing MATLAB.

Figure 4. The VMT graphical interface.
Figure 4. The VMT graphical interface.
Figure 5. MATLAB plot of primary (streamwise) and secondary (transverse) velocities in section 4 of Figure 3, generated with VMT.
Figure 5. MATLAB plot of primary (streamwise) and secondary (transverse) velocities in section 4 of Figure 3, generated with VMT.

Revolutionizing Velocity Mapping

In addition to VMT, USGS researchers use MATLAB to develop tools for analyzing time-series flow data, and tools that can be used to calibrate acoustic backscatter from an ADCP or similar Doppler-based instruments for continuous suspended sediment monitoring at existing USGS streamgages. The USGS has even supplied MATLAB code to ADCP manufacturers to help them improve their algorithms for calculating overall discharge. These tools, together with the VMT, are helping to change research and data analysis procedures for surface water hydrologists  worldwide.

The speed at which researchers analyze data with VMT has led to significant changes in the way studies are conducted. Today, researchers can run VMT on a laptop in the field and process ADCP data immediately in near real time. The results are used to guide further data collection in the area, if necessary. This approach was simply not possible in the past because the flow analysis could take months to complete and produced lower-resolution results.

Enabling Open Development

VMT is not merely a prototype, but a production application with an interface that makes it easy to use, even for scientists and researchers with no MATLAB experience. A key advantage of developing the application using MATLAB was that USGS scientists could apply their expertise as hydrologists to creating production software themselves, without relying on programmers. Throughout the development of the toolbox, VMT developers incorporated many ideas and scripts from the community of scientific MATLAB users.

The VMT developers from the USGS recently engaged MathWorks consultants to help improve the efficiency and performance of the MATLAB code and to enhance the interface layout. As part of this effort, the VMT code became more modular and that helped other users to improve and enhance it as part of an open-source development effort. The source code is available for download on Google Code.

About the Primary USGS VMT Developers

Dr. P. Ryan Jackson is a hydrologist and Dr. Frank L. Engel is a geographer at the U.S. Geological Survey. Both hold Ph.D.s from the University of Illinois at Urbana-Champaign, Dr. Jackson in civil engineering, and Dr. Engel in geography. Dr. Jackson specializes in environmental fluid mechanics and pairs an ADCP with water-quality instrumentation to study transport and mixing problems in rivers and lakes throughout the country. Dr. Engel specializes in fluvial geomorphology and studies of the interaction between flow evolution and sediment transport in meandering streams and rivers.

Original. Reposted by permission. MathWorks retains full copyright of this paper.

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