GIS
Geographic Information System. "A Geographic Information System is a computer system designed to allow users to collect, manage, and analyze large volumes of spatially referenced and associated attribute data.

The major components of a GIS are: a user interface; system/database management capabilities; database creation/data entry capacity; spatial data manipulation and analysis packages; and display/product generation functions."


GPS
Global Positioning System. A network of radio-emitting satellites deployed by the US Department of Defense.

Ground-based GPS receivers can automatically derive accurate surface coordinates for all kinds of GIS, mapping, and surveying data collection.