CATEGORY: Data Mining & Visualization

REVIEWER: Jean Timmerman, air resources specialist, Air Pollution Control District for San Diego County, California.

BACKGROUND: The primary goal of the San Diego County Air Pollution Control District is to protect the public from the harmful effects of air pollution and to achieve and maintain air quality standards. In order to make decisions that protect the public and to report accurate information to the Environmental Protection Agency (EPA), air pollution control authorities need good ways to analyze and display data. The prevailing winds above San Diego County are of special interest. We use air pollution and wind data as historical records in order to evaluate trends and origins of contaminated air. Often, transported air pollution is carried on the wind from Los Angeles to San Diego. Our agency is responsible for documenting air pollution that originated elsewhere, thereby avoiding EPA- administered fines for air pollution that is not organic to San Diego County.

PLATFORMS: PV-WAVE is available for the UNIX, Linux and Windows operating systems. We are running the Windows 2000 version of Visual Numerics PV-WAVE on a Dell Power Edge 2400 Server.

PROBLEM SOLVED: To provide the EPA with accurate information on prevailing winds, the Air Pollution Control District uses a windrose chart. This chart tells authorities how frequently the wind blows at a certain speed in a given direction. There are many applications and programs for studying windrose charts; however, most analyze only one specific data set at a time. For the type of work we do, it was necessary to use a program that can read data in the "AIRS" format, the universal format for the air monitoring community. PV-WAVE from Visual Numerics, Inc., was the only commercially available program we found that could read data from the many different sources that use the "AIRS" data format.

PRODUCT FUNCTIONALITY: We found that PV-WAVE's plotting capabilities were perfect for reading in and making sense of windrose chart data. Monitoring winds, however, is not the only work done by the Air Pollution Control District. We also encounter a number of graphics-type problems during our daily routine, including the need to visualize real-time air quality data. For these reasons, we needed more than a prebuilt application that restricted customization. We needed a tool that offered powerful data analysis and visualization functionality which could be customized to our specific needs. Because PV-WAVE is a fourth-generation programming language, it gives us the ability to write applications that address our specific data analysis problems.

STRENGTHS: PV-WAVE provides significant value not only because of its powerful visualization tools, but also the strong data analysis capabilities offered through Visual Numerics' IMSL Numerical Libraries, which are included in PV-WAVE. Other key strengths are PV-WAVE's ability to read many different data formats from many different sources and the ability it gives users to develop a customized solution.

WEAKNESS: The software's automatic typing for variables can be a challenge at times. With PV-WAVE, the type (integer, long, float, double) does not need to be declared and, in fact, may change with use. While automatic typing is a very powerful feature for writing compact and efficient code, debugging can be more difficult, especially for new users.

SELECTION CRITERIA: My group was first attracted to Visual Numerics after learning that PV-WAVE worked successfully in other projects within the Air Pollution Control District. Then, after seeing a successful demonstration with EPA data from Colorado, we became even more interested. We eventually decided to implement PV-WAVE for three primary reasons: it's a flexible product, giving us the ability to import many data formats and generate multiple views of windrose data; it's a complete solution combining state-of-the-art visualizations with advanced data analysis tools; and it's a stable product, meaning we won't lose valuable development time dealing with system failures or bugs.

DELIVERABLES: With the raw data from the windrose chart and PV-WAVE, we create a variety of reports and documents, primarily for the EPA, that graphically depict San Diego County's pattern of prevailing winds and transported air pollution.

VENDOR SUPPORT: Visual Numerics' technical support staff has been very accommodating. When we call for assistance, they quickly provide the knowledge and expertise we need to move forward.

DOCUMENTATION: PV-WAVE's online documentation is excellent. Most questions are easily answered without leaving your desk.

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