ELECTRIC CONSTANTS MEASURED IN VEGETATION AND IN EARTH AT FIVE SITES IN THAILAND
Abstract
Balanced two-conductor open transmission line probes were used to measure effective electric constants in vegetation and in the earth. Effective relative permittivity, and permeability in undergrowth at five dispersed sites were practically unity. Median effective conductivity of the undergrowth varied insignificantly between sites, but showed distinctive variation with frequency, from about 20 + or - 30% at 6 MHz to 300 + or - 30% (micro mho/m) at 100 MHz. In the few instances where measurements were made among mature trees the results were similar to those obtained for undergrowth. The most important parameters influencing vegetation constants were stem spacing (related to stem number density) and intrinsic stem conductivity (estimated to be between 0.05 and 0.5 mho/m). Ground-constant values varied greatly between sites, in a manner consistent with the variation of soil moisture content. Environmental forestry and soil surveys, summarized in the appendices to this report, are useful in explaining or applying the electric-constant results.
Document Details
- Document Type
- Technical Report
- Publication Date
- Dec 01, 1967
- Accession Number
- AD0674740
Entities
People
- H. W. Parker
- Withan Makarabhiromya
Organizations
- SRI International