This resource discusses Differential Global Positioning Systems (DGPS), and why they were developed. It provides a brief history of GPS and the selective availability mode which was formerly used to degrade accuracy for non-military purposes. Full description.

The International Association of Geodesy (IAG), one of seven associations within the International Union of Geodesy and Geophysics (IUGG), provides links to publications, meeting announcements, training, membership, and news articles. Full description.

This article describes the eqipment in use to simulate earthquake loading in materials at the Geotechnical Centrifuge Center at Rensselaer Polytechnic Institute. The equipment includes a centrifuge machine that can test a payload of 1 ton at 100g or 0.5 ton at 200g, a small in-flight computer-controlled earthquake simulator (shaker), a laminar rectangular box simulating the shear beam boundary conditions ... Full description.

This article discusses the use of selective availability to degrade the accuracy of Global Positioning Systems (GPS) for civilian use, and why it was eventually abandoned. Full description.

This slide presentation shows how three satellites are used to determine a position on Earth by triangulation. Full description.

This animated tutorial introduces users to Global Positioning Systems (GPS) technology. Topics include what GPS is, how it works, timing, satellite error, differential GPS, and how to use GPS. There is also a glossary. Full description.

This reference provides an overview of Global Positioning Systems (GPS) technology. Topics include the satellite network, how satellite signals are converted into geographic coordinates, sources of error, and differential GPS techniques. There are also links to documents and websites with additional information. Full description.

This lab activity, targeting grades 6-8, describes building a shake table and then exploring the dynamic response of various block structures to a simulated earthquake. Full description.

This lesson, based on the NOVA television broadcast 'The Day the Earth Shook', introduces students to engineering for earthquakes; specifically, architectural features that work and those that don't. The objective is to explore structural engineering through three design challenges; a relatively short, wide building; a home on a hillside; and a pyramid shape that focuses most of its mass near the ... Full description.