Hazard Advisor is a PRO level subscription feature and map overlay designed to show potential obstacle hazards in-flight. Using your GPS altitude and the high-res terrain data, it highlights obstacles and terrain in yellow and red. By default, hazards within 1000' of your altitude are highlighted in yellow, and hazards within 100' are shown in red.
There are two settings for Hazard Advisor, the activation speed (just called hazard advisor) and hazard altitudes. They can be found in the MAP View section of Settings. "Hazard Advisor" allows you to select the speed that Hazard advisor activates. Below that speed, ForeFlight will assume that you are taking off or landing and that low altitude will cause everything to be highlighted. We recommend that you set this to your standard rotation speed.
The other setting is "Hazard Altitude". This affects both Profile and Hazard Advisor. It allows that pilot to select the tolerances that Hazard Advisor activates. The options are Normal (red 100'/yellow 1,000'), Heli-Normal (red 50'/yellow 300'), Heli-Medium (red 25'/yellow 200'), Heli-Low (red 25'/yellow 100'). This allows for pilots to select an overlay that best suits their needs.