Accession Number : ADA193094

Title :   Surface-Wave Model Uncertainty Assessment.

Descriptive Note : Final rept. Sep 86-Oct 87,

Corporate Author : NAVAL OCEAN SYSTEMS CENTER SAN DIEGO CA

Personal Author(s) : Roy, T N ; Sailors, D B ; Moision, W K

PDF Url : ADA193094

Report Date : Nov 1987

Pagination or Media Count : 72

Abstract : The GROUNDWAVE model is compared to 84 surface-wave measurements made at frequencies of 20, 50, and 101.5 MHz for mountainous, hilly, and flat terrain. Surface wave transmission loss error is evaluated as a function of distance, frequency, terrain and receiving antenna height. The overall average measured transmission loss is 144 dB with an average interdecile range of 11 dB. The overall average calculated transmission loss is 141 dB, well within the interdecile range. When the model was tested as a function of terrain type, a trend toward understanding the transmission loss as the terrain became more irregular was apparent. GROUNDWAVE model error is evaluated as a function of input effective ground conductivity and effective ground relative dielectric constant also. By using constant values for these ground frequency, as is the usual practice, the possibility exists for substantial error in transmission loss calculations as a function of frequency. In the frequency range 2 to 20 MHz, results how the GROUNDWAVE model to underestimate transmission loss by an average of 13.1 dB for desert, mountainous, and hilly terrain. For the rich agricultural and marsh terrain, the GROUNDWAVE model overestimated the transmission loss by an average of only 1.9 dB. When the GROUNDWAVE model predicted transmission losses were compared to measured over-ocean data, it was found that the model severely over-predicted at frequencies greater than 18 MHz. This was attributed to the inability of the model to input nonstandard atmospheres.

Descriptors :   *TRANSMISSION LOSS, *GROUND WAVES(ELECTROMAGNETIC), *SURFACE WAVES, ANTENNAS, ATMOSPHERES, CONDUCTIVITY, DIELECTRIC PROPERTIES, GROUND LEVEL, HEIGHT, INPUT, MODELS, SURFACE WAVES, TERRAIN, WETLANDS

Subject Categories : Radiofrequency Wave Propagation

Distribution Statement : APPROVED FOR PUBLIC RELEASE