HTZ generates contours according to FCC rules. These are applied for coverage of services for FM broadcast, TV and land mobile radio. This methodology gives an approximate coverage and interference and the contours use different reliability values in the curves. Each contour is represented as a contiguous polygon with areas with no coverage shown.
However, FCC contours do not apply to AM broadcast. HTZ encapsulates the groundwave model with a conductivity map loaded for a given area. The coverage contours can then be extracted for the values 0.5mV/m (54dBµV/m) and 2mV/m (66dBµV/m).
Alternatively, HTZ features a Threshold limited polygon function, which replicates contours identified by FCC, with a difference of around +/1dB. To support this function, ATDI has produced a dataset (DTM and conductivity) with a 90m resolution. This dataset is created from a 30m dataset of the USA, available via the Map Download Manager for the DTM and the FCC conductivity map (AM_m3), which is also available for download.
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