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Redwood City Police Department System Performance � by dividing the service area into a grid of"tiles" and examining the � characteristics of the Radio Fre4uency signals as the travel between each radio infrastructure site and each tile. This is a vast improvement over methods that rely on determining coverage on a number of radials emanating from a radio infrastructure site. By the radial method, even if the service azea is examined every 5 degrees, at just over 10 miles from the site, areas close to three- quarters of a square mile will receive no examination. Considering that'MOZAIKSM has the ability to evaluate tiles as resolute as 3 are seconds as contained in the USGS data base, this difference in methodology becomes even greater. MOZAIKSI"I bases its calculations on the models described in the following references: I. "Radio Propagation for Vehicular Communications",Kenneth Bullington, IEEE Transactions on Vehicular Technolo�v, Volume VT-26,Number 4,November 1977. 2. "Field Strength and Its Variability in VHF and UHF Land- Mobile Radio Service", Yoshihisa Okumura,Review of the Electrical Communication Laboratorv Volume 16,Number 9-10, September and October 1968. - - Environmental losses due to the presence of obstacles such as buildings and trees are often overloaked by propagation prediction models. This is not the case with MOZAIKSM. Motorola's propagation prograin can account for the 0 dB to 12 dB range in environmental losses at 800 MIiz due to the effects of trees and other foliage. Additionally,the losses due to buildings that vary from 2 dB in rural azeas to 20 dB in urban areas are included in all - MOZAIKSM calculations. The worst of the two figures for trees and buildings is used(rathez than the sum) as buildings and trees cannot exist at the same location. To accurately locate these cluttered areas,the MOZAIKSM model utilizes the USGS Land Use- Land Coverage(LULC)database. The LULC database associates various classifications of land(such as residential, commercial,industrial,orchazds, forested,etc.)with digitized terrain data and ascribes the appropriate loss factor to accurately evaluate each tile for coverage reliability. The coverage predictions have been based on the combined CAD message model included in the system capacity section of this proposal. Different lengths or quantities of inessages will have an QMO�ra,�o�..4 , 3 - 15 _ _ . __ _ _