What does "above sea level mean"?

Question

When pilots say we are "250,000 metres above sea level" what does that mean? Is it from the take off ground to where ever the plane is in the air/sky measures 250,000 metres? or what?

Answer 1

Try this http://en.wikipedia.org/wiki/Sea_level

Answer 2

Mean Sea Level

Answer 3

Is Mean sea level, sort of average sea level. Sea Level change with Tides so when Ordnance Survey Maps drawn a Mean Sea Level was introduced. This approximately half way between high and low tides and all maps relate to this. Tidal Range at Clevedon in England is 40 feet so this is a significant amount. Some say sea levels change but there are photographs in Antartica where there is no significant Tidal effect taken by Captain Scotts Party in 1910 approx which show the same sea level on the same rocks as measured in 2000. so sa level rise is no sense.

Answer 4

The average height of the sea surface water level. For the United States, it is computed by averaging the levels of all tide stages over a nineteen year period, determined from hourly height readings measured from a fix, predetermined reference level. It is used as a basis for determining elevations, as the reference for all altitudes in upper air measurements, and as the level above which altitude is measured by a pressure altimeter for aviation. Often referred to as MSL.

In the air, altitude can be measured by ranging a radar signal down to the ground if the ground is at a known elevation. Without knowing the ground elevation, a measure of air pressure will convert to an altitude.

If the pilot says you are at an altitude of 30,000 feet, and you are flying over Mount Everest, then the plane is very close to the mountain. A plane's altitude is above sea level not ground level. That is why planes adjust the barometric instrument on the plane and set the altitude of the airfield to zero, so they will know how far above the ground they are.

Answer 5

Sea Level is an imaginary level around the whole surface of the earth where the sea would be if there were no tides or land. Most airports are above sea level. For example Denver is about 5000 feet above sea level. So a plane taking off from Denver could be 6000 feet above sea level and only 1000 feet above the ground. So you can see why it is important to know how many feet above Sea Level the mountains that you are flying over are.

Answer 6

it means 250,000 metres above sea level, as simple as that. it's the lowest most surface on the earth from which all distances to the air is measured.

if the pilot said "250,000 metres above ground", then people would ask "what ground are you talking about? Denver is at a higher elevation than New York City."

Answer 7

Sea level is based on the oceans mean level. As places like Nepal, Mexico city is all high above sea level (being on an elevated land like himalayas) or Holland being below sea level, ie the land is sunken. hence the need for dikes.

With the mean sea level, 0 metres, pilots can gauge how far up they are. ie you are flying from USA approximately 10m above sea level but Nepal is about 2500m up in the mountains.

Answer 8

The term above mean sea level refers to the elevation (on the ground) or altitude (in the air) of any object, relative to the average sea level.

Mean sea level (MSL) is the average (mean) height of the sea, with reference to a suitable reference surface. Defining the reference level however, involves complex measurement, and accurately determining MSL can prove difficult.

Answer 9

term above mean sea level (AMSL) refers to the elevation (on the ground) or altitude (in the air) of any object, relative to the average sea level. AMSL is used extensively in radio (both in broadcasting and other telecommunications uses) by engineers to determine the coverage area a station will be able to reach. It is also used in aviation, all heights are recorded and reported with respect to AMSL (though also see flight level).

i am not sure what ir means too hope you can simplify it for me

Answer 10

Sea level is defined as the level of bodies of water as oceans and seas where the pressure at that elevation is one atmosphere(14.7 lbs/in^2.or 1.01325x10^5 Newtons per meter square)Note not all seas are at the same level.
The altimeter on an aircraft indicates the high in term of sea level at that Reference pressure. The altimeter calculates altitudes in terms of pressure.
However there are not that many pilots flying at 160 miles above sea level.That is above 80000 feet. Commercial airliners fly only within the range of 45000 feet.

Answer 11

Sea level is just that, the level of the sea. All altitudes are measured using the level of the sea as the 'zero' starting point. In Death Valley Califonia, there are places that are actually below sea level.