Yes it is measured in feet or metres. Most countries with a coast measure it from a mean high tide at a given point.
The height or the altitude of the land is its distance above sea level. This is referred to as the elevation of the land.
The height above or below sea level is "elevation". Altitude is used only for distance above sea level.
We call this "elevation".
Dry land is usually above sea level.
the height of land above or below the level of the ocean or sea level
It could be called the elevation or altitude of the particular land-form.
Altitude is a noun meaning the height above sea level or the earth's surface. Here are some sample sentences. "The search and rescue helicopter was flying at an altitude below 100 feet." "The air traffic controllers had the incoming planes fly at different altitudes to avoid collisions while they awaited permission to land." The altitude of the highest mountain range in the world is above 8,000 meters above sea level.
elvation
...a good thing for air-breathing creatures.
ALL "land" is technically "above sea level" - it runs from 0 ft to the top of Mt Everest.
Elevation if on land Altitude if airborne above the ocean That will change depending on where you are in the world. A mapping application such as Google Earth will give you the elevation of most places on Earth with an accuracy of a few meters.
elevation maps are maps that show you the height of land above sea level