Automatic Barometer Corrections Spreadsheet - (XLS) - Courtesy of Princo Instruments, Inc.
Elevation Correction Tables for Barometric Pressure Sensors - (PDF) - Based upon the United States Standard Atmosphere.
GPS Versus Barometric Altitude: The Definitive Answer - What's 'GPS altitude' and what's 'barometric altitude'? And what's the difference? And does it matter? This article, first published in issue 123 of Cross Country magazine, May 2009, explains all you need to know about the 'barometric versus GPS altitude' issue.
Online Meteorology Guide: The Pressure Module - University of Illinois
Pressure Altitude Equivalents - A simplified table based upon the United States Standard Atmosphere
Pressure Conversion Table - Use this table to convert barometric pressure readings from millibars to inches of mercury to millimeters of mercury.
The Aneroid Barometer and How To Use It - Australia Bureau of Meteorology
How to Use a Fortin or Kew Pattern Mercury Barometer - The UK's National Measurement Laboratory provides instructions for setting up a barometer and calculating pressure from the barometer readings. Also offers information on transportation of mercury barometers.