Pima County Department of Transportation

Geographic Information Services Division

About the Geographic Data Library

General

• GIS Library Overview

• Metadata - Descriptive information about each dataset.

• Viewing, Using and Downloading GIS Library Data

• GIS Layer Field Names and Standard Fields, aka "stump" fields.

• The Surveying System in Pima County: Townships, Ranges, and Sections.

• Situs (Property) Addresses

• Glossary of terms

Coordinate Systems

• Arizona Coordinate System, 1983

• Projection Parameters and Projecting Our Data

• Measurement Units: International Foot vs. US Survey Foot

• The advantages of using NAD 1983 instead of the older NAD 1927 Datum are described in The Problem With NAD 27 by Bill Strange, National Geodetic Survey (Retired).

• The National Geodetic Survey's FAQ's about Datums, GPS and Positions