The system used data available from the National Earthquake Information Center (NEIC), part of the US Geological Survey. This data provides basic information about earthquakes within hours of them taking place. In reponse to a query, the data was dynamically accessed from a USGS server in Golden, Colorado. The data was then processed into an appropriate format in Edinburgh and finally displayed using the Xerox PARC Map Viewer based in Palo Alto, California again in the USA.
Some interesting principles relating to internetworking were demonstrated:
- Unusually, each of the components of this system (the interface, the data and the display display software) are physically remote from the user and from each other. This is an example of a truly Distributed GIS.
- Yet, it remains dynamic, both in terms of the data used and the display
- Using the Web, global accessibility is achieved, with no dependency on having the appropriate software to display the data (other than a web browser)
- The speed of accessing the maps is related to network connectivity to Palo Alto, not Edinburgh. If you think about it, this is interesting. In principle the interface in Edinburgh could direct you towards your nearest server (if there were map servers distributed regionally), hopefully to get access to regional maps or even just to achieve the best possible graphics performance. (Palo Alto is within a mile of the San Andreas fault, so it would be quite nice not to be dependent on a map server in Palo Alto if a quake occurs there!)
- Whereas some other maps of earthquakes are up to a week out-of-date, the dynamic nature of this interface means not only are the maps as recent as the earthquake records, but maps can be zoomed and panned to suit particular user requirements.
Since 2003, the mapping for the site has been provided by Mapserver. This is open-source software for constructing spatially enabled Internet-web applications. It allows the current earthquake data to be displayed on a world-map, using the longitude and latitude information provided by the USGS.
In 2004, an earthquake catalogue was added to the site, allowing users to search for specific earthquake data and to display it on a map. This also allowed the introduction of an algorithm (a type of calculation) which produces predictions of where the next very large earthquake might occur.
In 2005, the source for the earthquake data was changed from the USGS's ftp data to their RSS data. RSS (which stands for Rich Site Summary) is a format in which news headlines and other information can be distributed across the internet. A dynamic earthquake animation was also added, using Scaleable Vector Graphics (SVG). The animation is produced using data extracted from the earthquake catalogue, and automatically updates each day.
Bruce M. Gittings,