Temporal Weather Impacts Upon Exterior Intrusion Detection Systems,

Fundamentally, an electronic exterior intrusion detection system IDS cannot directly detect intruders it detects a variation in the condition being monitored, extracts characteristics of that variation, and assesses whether such a variation probably is caused by an intruder. However, exterior IDSs do not operate in a benign natural environment. Their environment is constantly changing as a result of solar driven energy and moisture fluxes that create the weather. These weather changes often cause variations in the conditions being monitored by IDSs. The challenge, therefore, is to recognize how and when IDSs ore responding to some change in their natural environment, rather than to intruders. This report is a technical analysis of causes of weather driven temporal changes in the environment that impact the operational efficiency of IDSs. The report is intended to assist security designers in selecting suitable IDSs for a site and to assist security managers in operating IDSs at the required level of reliability. This is accomplished by identifying temporal variations in weather that are sufficiently general to be identified as patterns, and by identifying how different IDS phenomenologies respond to these patterns. The result is an understanding of how weather conditions influence the ability of types of IDSs to detect reliably activities representative of an intruder while successfully discriminating against weather created conditions within a detection zone. The main body of the report is organized by temporal scale diurnal, quasiperiodic, and seasonal. Within each temporal scale, weather processes common at that scale are explained. Topics covered include air and soil temperature, soil moisture, precipitation, snow cover, winds, fog, storms, urban and topographic effects, vegetation effects, and solar radiation.