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This paper compares precision field-strength
measurements taken by a Rohde & Schwarz FSH-3
portable spectrum analyzer with simulation results derived
from the ITM coverage prediction model (Irregular
Terrain Model), also known as NTIA-ITS Longley-Rice
model, in conjunction with the 3-arc-second SRTM
(Satellite Radar Topography Mission) geographical data,
the propagation predictions of ITU-R Recommendation
P.1546 and those of the empirical Hata-Davidson model
using HAAT. ITU-R P.1546 and Hata-Davidson models
exhibit higher errors at longer distances and therefore
necessary corrections should be introduced in the models
in order to increase propagation prediction accuracy.
Especially, measurements results show that ITU-R P.1546,
on average, underestimates the field strength at distances
longer than 50 km. The Longley-Rice model using the
terrain digital elevations is more accurate, as expected,
and its results are closer to the measurement data.