If the map shows "Poor" or "No Coverage" for the nearest major city, you may need a large, outdoor directional antenna mounted on a rotor, plus a pre-amplifier. The map helps you aim the antenna precisely at the transmitter coordinates provided in the station's data sheet.
Government maps systematically over-predict coverage due to: dtv gov maps
Empirical study (FCC OET 2017): At 35 dBμV/m contour, actual success rate for indoor reception is only 23-41%. If the map shows "Poor" or "No Coverage"
The most critical feature for the user is the color-coded signal strength indicator. Understanding these colors is the difference between a crystal-clear picture and a black screen: Empirical study (FCC OET 2017): At 35 dBμV/m
During hurricanes, wildfires, or power outages, internet and cable fail. OTA DTV often survives. Emergency managers use these maps to identify "dead zones" where battery-powered TVs won't work, so they can deploy generators or satellite relays.