old (2001) slideshow with some good information on NGVD, &c.

GIS gain much of their power from being able to collate and cross-reference many types of data by location.

GPS antenna and lightning suppression system installed on a mast

random photo of a British surveyor using GPS in the field w/ tablet PC

OPUS allows users to submit their GPS data files to NGS, where the data will be processed to determine a position using NGS computers and software

What GPS application do you need?

good definition with coordinate systems and figure of the earth

The latest surveying and GPS technology create a complete GIS of a sunken battleship from the attack on Pearl Harbor

Schematic diagram showing the relationship between local mean sea level, the geoid, and local ocean dynamic topography

Schematic diagram showing the relationship between the geoid, orthometric heights and ellipsoid. Note that the ellipsoid is drawn above the geoid. This is the actual case for all points in the conterminous United States

Scematic diagram showing some of the “level surfaces” of the Earth, including the geoid, and relation to the Earth’s crust and local mean sea level

creative method of contextualising photographs by time and geography

A history of the relation of geology during the first 110 years of the U.S. Geological Survey to the development of public-land, Federal-science, and mapping policies and the development of mineral resources in the United States