Thursday, 17 January 2002: 9:44 AM
A comparison of the Stedman's Heat Index and the WBGT Index
Human comfort level is measured in terms of environmental factors. Temperature, humidity, wind, and radiant energy all contribute to how the body feels and responds. Excess heat and moisture can result in physiological stress, perhaps thermal exhaustion or even death. There are several indices that quantify human comfort levels, relating environmental factors to physiological response. Most involve empirical algorithms that are functions of various environmental parameters. The Stedman's Heat Index is one of the more common comfort indices that is a function of temperature and relative humidity. The National Weather Service, among other organizations, routinely report values of the Stedman's Heat Index as guidance for stressful situations. Another index, the Wet Bulb Globe Temperature (WBGT) is used by the military to measure environmental factors and then determine an appropriate level of physical training.
This study will focus on developing an algorithm to transform from the Wet Bulb Globe Temperature (WBGT) Index to the Stedman's Heat Index. While WBGT may be relatively easy to determine using a simple instrument that measures ambient, wet-bulb, and a radiant temperature which are combined to yield the index, it is somewhat labor intensive. An automated system currently in place at the United States Naval Academy provides up-to-date Steadman Heat Index values available on the web. The purpose of this month long study will provide the a database to make the transformation between the two indices and apply the same (or closely similar) criteria for physical exertion.