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The 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 datum. 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, where most heights are recorded and reported with respect to AMSL (see flight level), and in the atmospheric sciences.

Definition[link]

The concept of a "mean sea level" is in itself rather artificial, because it is not possible to determine a figure for mean sea level for the entire planet, and it varies quite a lot even on a much smaller scale. This is because the sea is in constant motion, affected by the high and low pressure zones above it, the tides, local gravitational differences, and so forth. The best one can do is to pick a spot and calculate the mean sea level at that point and use it as a datum. For example, the Ordnance Survey uses a height datum based on the measurements of mean sea level at a particular gauge at Newlyn, Cornwall from 1915 to 1921^[1] for their maps of Great Britain, and this datum is actually some 80 cm different from the mean sea level reading obtained on the other side of the country. An alternative is to base height measurements on an ellipsoid of the entire earth, which is what systems such as GPS do. In aviation, the ellipsoid known as World Geodetic System 84 is increasingly used to define mean sea level. Another alternative is to use a geoid based datum such as NAVD88.

Usage[link]

When referring to geographic features such as mountains on a topographic map, variations in elevation are shown by contour lines. The elevation of a mountain denotes the highest point or summit and is typically illustrated as a small circle on a topo map with the AMSL height shown in either metres or feet or both.

The height above average terrain (HAAT) for a station is determined from topographic maps by averaging the elevation AMSL at points along several radials or radii. This is subtracted from the elevation AMSL of the antenna, including both the tower itself and the ground it is on, to determine the difference. Negative numbers for HAAT sometimes result from this when the station or airport is in a valley, which is significantly lower AMSL than the surrounding mountains. In the rare case that a location is below sea level, AMSL itself is a negative number. For one such case see Amsterdam Airport Schiphol.

AMSL is also important to engineers in high-elevation areas because some equipment is not designed with enough airflow for sufficient cooling in the thin air, which can cause overheating, damage and failure of the electronic components within a transmitter.

See also[link]

• Above ground level
• For sample AMSL elevations, see,
  • 1 E3 m
  • List of mountains
  • Ranges, peaks and passes of the Alps
• Orthometric height
• Normal height
• Geopotential height
• Normaal Amsterdams Peil
• Normalhöhennull
• Metres above the Adriatic
• Extreme points of Earth

References[link]

Michelle Thomas (died December 22^[3][4][5] or 23, ^[6][7] 1998) was an American actress. She was best known for her roles as Justine Phillips (girlfriend of Theo Huxtable) on the NBC sitcom The Cosby Show, and as Myra Monkhouse (girlfriend of Steve Urkel) on the ABC/CBS sitcom Family Matters.

Early life and career[link]

Born in Boston, Massachusetts,^[8] Michelle Thomas grew up in Montclair, New Jersey and was an alumna of West Essex High School. She was the daughter of Phynjuar Thomas, a stage actress, and Dennis Thomas, a member of music group Kool & the Gang.^[6] In 1984, Thomas was crowned Miss Talented Teen New Jersey in Hal Jackson's Talented Teen Competition.^[9] The following year, she competed in the international pageant and won the title of International Queen.^[10]

In 1988, Thomas played Justine Phillips, the girlfriend of Theo Huxtable on The Cosby Show. She later appeared on various television programs during the late 1980s and 1990s including A Man Called Hawk and Thea. She had a role on a TV movie, Dream Date, in 1989. In 1991, she had a small role in Hangin' with the Homeboys. She also appeared in music videos for Mint Condition, Dru Hill and Chubb Rock. In 1993, she won the role of Myra Monkhouse on the long-running sitcom Family Matters. After the series ended in 1998, Thomas portrayed Callie Rogers Stark, an aspiring singer on the CBS soap opera The Young and the Restless. She left the series in October 1998.

Death[link]

In August 1997,^[7] Thomas was diagnosed with a rare form of stomach cancer, intra-abdominal desmoplastic small round cell tumor.^[10] She underwent surgery to remove a lemon-sized tumor shortly before landing her Young and the Restless role in the spring of 1998. In October 1998, she underwent surgery after a second cancerous growth ruptured. After being released from the hospital, Thomas flew home to New Jersey to spend Thanksgiving with her family.

On December 22 or 23, Thomas died surrounded by her family and friends in New York City at Manhattan's Memorial Sloan-Kettering Cancer Center,^[11] aged 29^[8][12][13] or 30.^{[4][7][10][11]} On December 26, 1998, a Muslim funeral service was held, as Thomas had requested. She was buried in Montclair, New Jersey, near her home.^[7]

Filmography[link]

Award nominations[link]

Notes[link]

External links[link]

• Michelle Thomas at the Internet Movie Database
• Michelle Thomas at Find a Grave