WeatherSVG, A Dynamic Weather SVG Web Service

The US Air Force Weather mission is to provide accurate, relevant and timely air and space weather information to many users. Weather products are generally in three formats: imagery, text, and binary files. Weather forecast model results are stored in the binary format. They represent the predictive values of specific weather parameters (such as temperature or pressure) at a particular height and rectangular lattitude\longitude bounds. The models are stored in a binary general-purpose, bit-oriented data exchange format, known as GRIB (short for Gridded Binary). This standard is maintained by the World Meteorological Organization.

As the US Air Force transitions to a network-centric enterprise architecture, the Air Force Weather Program will provide services to a greater diversity of clients. These consumers, such as mission planning applications, require the information in forecast models but do not necessarily want to spend the resources developing GRIB parsers. In a service-oriented architecture, clients want data without having to become entrenched in the complicated ontology of the data producers. WeatherSVG, an SVG Web Service, solves this issue by translating the forecast models into an readable, standardized, visual format: Scalable Vector Graphics.

WeatherSVG, a WS-I compliant Web Service, receives forecast model results (in GRIB Format) and outputs an SVG visualization of the input. The gridded data is separated into separate bins using quantile classification. The gridded data is segmented using a standard blob detection algorithm, with each blob representing a group of adjacent points with values in the same classification bin. A novel polygon creation algorithm defines one or more rings of vertices around the edges of the blobs. Each polygon represents a particular value of a weather parameter for a given area. The polygons are assigned a particular color corresponding to its inherent classification value. The weather parameter shapes are overlayed on a cropped and geo-rectified dynamic map.

WeatherSVG provides a custom translation for wind forecasts. Upon receiving wind model data, WeatherSVG produces wind barbs that specify speed and direction. The appearance of the wind barbs is in a format recognized by weather forecasters.

In the request to WeatherSVG, the client can configure a number of optional parameters:

WeatherSVG has two clients, a PC client and a PDA client. The PC client is written with C# and runs on Windows XP. The PDA Client is written with C# and runs on Pocket PC 2003. Both clients retrieve a link to the forecast model from an Air Force weather dissemination Web Service known as the Joint Weather Impact System (JWIS). They send to JWIS a time range, location, and desired weather parameter. JWIS responds with an http link to the prepared forecast model data. The clients send the outputted forecast model link to WeatherSVG. WeatherSVG downloads and processes the forecast data and returns with the SVG visualization of this data. The clients display the returned SVG results. The PDA client displays Wind SVGs with an embedded script. This script displays meta information about individually selected wind barbs.

This prototype displays the power and possibilities of an SVG Web Service. WeatherSVG demonstrates how to distribute the visualization process across multiple computers to compensate for constrained nodes (PDA Clients). The Web Service interface of WeatherSVG facilitates fast development time for the client; the arduous task of parsing the forecast GRIB files is alleviated. In an enterprise system, SVG Web Services will become an essential aspect for service oriented visualization solutions.

Paper title: Weather SVG, A Dynamic Weather SVG Web Service
Paper Authors: Samuel Epstein, John Klingler
Authors Company: The MITRE Corporation, 202 Burlington Rd, Bedford, MA 01730-1420
Authors email: sublime@mitre.org, jmkling@mitre.org
Authors work phone: (781)-266-9512, (781)-266-9516