A league
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That's a very old term!
Nautical miles
Nautical miles are called "Knots". As in, "We were making 4 knots!"
Measuring distance on the sea is typically in Nautical Miles. The nautical mile has been standardized to 1852 meters.
meters
A kilogram is a measure of weight. A gallon is a measure of liquid volume. You cannot convert one to the other. You can, however, convert gallons to liters. 9 gallons is equal to 34.06871 liters. Actually a kilogram is a measure of mass. A kilogram at sea-level weighs 9.8 Newtons. Also at sea level a kilogram has a weight of 2.2 pounds.
Kg is the abbreviation for kilogram, a unit of mass (or weight) Bar is a unit of pressure often used in describing atmospheric pressure, but also used in other contexts. Standard sea-level atmospheric pressure is slightly less than one bar.
elevation above sea level . . . barometer or GPS air temperature . . . thermometer air pressure . . . barometer
A not-commonly-used measurement is 'atmosphere'. One atmosphere is the average pressure at sea-level: 101.325 kPa, 1013.25 mbar, 29.921 inches of mercury (inHg) or 760 millimeters of mercury (mmHg).
Yes, mean sea level (MSL) is the average (mean) height of the sea.
A kilometre. A megametre may be more appropriate but it is not a unit that is used much.
miles
Its height (above mean sea level): metres Its length: kilometres - or metres if it is a really short trail.
Sea level is a standard 'height' from which you can measure the relative height of objects (ie. cities) as such, high above sea level would refer to something 1,000+ metres above sea level... or whatever definition you think appropriate.
Use positive numbers for altitudes above sea level, zero is sea level itself, and negative numbers for altitudes below sea level. As for the picture, use a number line - but make vertical instead of using the commonly used horizontal position.
metres above the mean sea level
A kilometre.
Haga is the brand name. An altimeter is used to measure altitude, which is how high you are above sea level.
The international standard unit for measuring pressure is the pascal. 1 pascal = 1 newton / square meter. A unit commonly used is the bar; 1 bar = 100,000 pascal; and that's the approximate air pressure at sea level. Older units that are still sometimes used include mmHg (millimeter mercury).
A kilogram is a measure of weight. A gallon is a measure of liquid volume. You cannot convert one to the other. You can, however, convert gallons to liters. 9 gallons is equal to 34.06871 liters. Actually a kilogram is a measure of mass. A kilogram at sea-level weighs 9.8 Newtons. Also at sea level a kilogram has a weight of 2.2 pounds.
The height of a landform on Earth is DEFINED as its height above sea level since sea level is the closest thing on Earth to a constant or standard starting point. Sea level itself changes with the tides and wind and weather, so we use what is called "mean sea level" which is an average of measured levels at a given place over an extended time.
Altitude