NOTICE: The project that is the subject of this report was approved by the Governing Board of the National Research Council, whose members are drawn from the councils of the National Academy of Sciences, the National Academy of Engineering, and the Institute of Medicine. The members of the committee responsible for the report were chosen for their special competences and with regard for appropriate balance.

Support for the activities of the Mapping Science Committee is provided by the National Imagery and Mapping Agency (NMA202-99-1-1018), the U.S. Geological Survey (99HQAG0193), the Federal Geographic Data Committee, the Bureau of Transportation Statistics (DTTS59-99-P-00257), the National Oceanic and Atmospheric Administration (56-DKNA-0-95106), and the Bureau of the Census (43-YA-BC-037424). Any opinions, findings, conclusions, or recommendations expressed in this document are those of the authors and should not be interpreted as necessarily representing the views of the agencies that provided support for this project, or of the official policies, either expressed or implied, of the U.S. Government.

Cover: Aerial photo courtesy of the U.S. Geological Survey. The image on the bottom of the page was dowloaded from PhotoDisc.