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metar kttn 051853z 04011kt 1/2sm vcts sn fzfg bkn003 ovc010 m02/m02 a3006 rmk ao2 tsb40 slp176 p0002 t10171017= [14] METAR indicates that the following is a standard hourly observation. KTTN is the ICAO identifier for the Trenton-Mercer Airport .
A chart datum is the water level surface serving as origin of depths displayed on a nautical chart and for reporting and predicting tide heights. A chart datum is generally derived from some tidal phase, in which case it is also known as a tidal datum. [1] Common chart datums are lowest astronomical tide (LAT) [1] and mean lower low water (MLLW).
In aviation, atmospheric sciences and broadcasting, a height above ground level (AGL [1] or HAGL) is a height measured with respect to the underlying ground surface.This is as opposed to height above mean sea level (AMSL or HAMSL), height above ellipsoid (HAE, as reported by a GPS receiver), or height above average terrain (AAT or HAAT, in broadcast engineering).
Global MSL refers to a spatial average over the entire ocean area, typically using large sets of tide gauges and/or satellite measurements. [ 5 ] One often measures the values of MSL with respect to the land; hence a change in relative MSL or ( relative sea level ) can result from a real change in sea level, or from a change in the height of ...
The amount of time it takes for the sound or light to travel through the water, bounce off the seafloor, and return to the sounder informs the equipment of the distance to the seafloor. LIDAR/LADAR surveys are usually conducted by airborne systems. The seafloor topography near the Puerto Rico Trench Present-day Earth bathymetry (and altimetry).
In the above table, geopotential altitude is calculated from a mathematical model that adjusts the altitude to include the variation of gravity with height, while geometric altitude is the standard direct vertical distance above mean sea level (MSL).
Aviation altitude is measured using either mean sea level (MSL) or local ground level (above ground level, or AGL) as the reference datum. Pressure altitude divided by 100 feet (30 m) is the flight level , and is used above the transition altitude (18,000 feet (5,500 m) in the US, but may be as low as 3,000 feet (910 m) in other jurisdictions).
In the US, there are specific VFR cruising altitudes, based on the aircraft's course, to assist pilots in separating their aircraft while operating under visual flight above 3,000 ft above the surface (AGL) but below 18,000 ft Mean Sea Level (MSL). Unofficially, most pilots use these rules at all levels of cruise flight.