Map Reference Resources: Tools and Definitions

From the Map History/History of Cartography site; contains links to resources on distance; longitude, latitude and Prime Meridians; map projections; mountains; and scale

An online interactive computation of geodetic values; includes links to a variety of conversion utilities

All lands in the public domain are subject to subdivision by this rectangular system of surveys, regulated by the U.S. Department of the Interior, Bureau of Land Management (BLM); this article from the USGS tells the history of the PLSS and explains how it works

The State Plane Coordinate System is a set of more than 100 different coordinate systems using different projections; this article from the Virtual Terrain Project explains its origins and how it works

USGS Fact Sheet 077-01 (August 2001) explains the Universal Transverse Mercator (UTM) Grid and how to determine a UTM grid value for a map point

Per their Web site "look up the exact location of millions of places."

Converts address to GPO coordinates and latitude/longitude.

The Department of the Army Technical Manual (TM30-548) available as a PDF file from HathiTrust

Legend for USGS topographic maps

Online poster from USGS detailing various map projections.

An overview of how map projections work created by National Geographic

USGS Fact Sheet provides an overview of map scales with a focus on common scales used by the U.S. Geological Survey