The difference between Pressure Altitude,True altitude and Absolute Altitude, let's make sure we're on the same page...
..."Constantly changing, absolute altitude is the distance measurement of your airplane above the ground. Expressed in "feet AGL" (above ground level), you can also find many obstacles and airspace classifications that exist in feet above the ground.

A radar altimeter (or radio altimeter) measures altitude above the terrain presently beneath an aircraft by timing how long it takes a beam of radio waves to reflect from the ground and return to the plane. Radar altimeters generally give readings up to 2,500 feet AGL."...
..."True altitude is the vertical distance of your airplane above sea level. Commonly expressed as "feet MSL" (feet above mean sea level), many of the airspace altitudes, terrain figures, airways, and obstacles you'll find on aeronautical charts are expressed in true altitude (MSL), feet above sea level."...

..."When you set your altimeter to 29.92, you're flying at standard pressure altitude. This is the altitude of the aircraft above the standard datum plane, the theoretical location where at 15 degrees Celsius the altimeter setting will equal 29.92 inches of mercury. Many of the calculations you'll find in your POH require knowledge of what pressure altitude you'll be flying at.
All aircraft flying above 18,000 feet MSL are required to set their altimeters to 29.92 inches Hg (in the US). This means that all aircraft flying in the flight levels will have the same altimeter setting."...
Helicopters often perform "hovering" and "low-level" flying, meaning they stay at altitudes below 500 feet above ground level (AGL), especially when engaged in operations like emergency medical services, police work, and search and rescue missions, where precise maneuvering close to the ground is necessary.
https://www.boldmethod.com/blog/lists/2025/01/the-five-types-of-flying-altitudes-explained/
https://wtop.com/local/2025/02/recovery-crews-return-to-the-potomac-debris-after-the-deadly/
Are you trying to tell me that aircraft landing and taking off regularly fly within 100' of helicopter traffic?......that's insane
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