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Since gravity is not constant over large areas the orthometric height of a level surface (equipotential) other than the reference surface is not constant, and orthometric heights need to be corrected for that effect. For example, gravity is 0.1% stronger in the northern United States than in the
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height differences by correcting for gravity variations. Practical applications must use a model rather than measurements to calculate the change in gravitational potential versus depth in the earth, since the geoid is below most of the land surface (e.g., the
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southern, so a level surface that has an orthometric height of 1000 meters in one place will be 1001 meters high in other places. In fact, dynamic height is the most appropriate height measure when working with the level of water over a large geographic area.
87:, and various countries may choose to operate with those definitions instead of orthometric. They may also adopt slightly different but similar definitions for their reference surface.
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may be chosen for large-scale hydrological purposes. Heights for measured points are shown on
National Geodetic Survey data sheets, data that was gathered over many decades by precise
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at one point rather than to any location's exact mean sea level. Orthometric heights are usually used in the US for engineering work, although
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Hwang, C.; Hsiao, Y.-S. (2003-08-01). "Orthometric corrections from leveling, gravity, density and elevation data: a case study in Taiwan".
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ten-year program to obtain such data with a goal of releasing a new geoid model as part of the
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49:. Orthometric height is one of the scientific formalizations of a layman's "
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Paul R. Wolf and
Charles D. Ghilani, Elementary Surveying, 11th ed. p. 581
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US Department of
Commerce, NOAA; US Department of Commerce, NOAA.
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requires accurate gravity data for that location; in the US, the
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from a point of interest to a reference surface known as the
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Hofmann-Wellenhof and Moritz, Physical
Geodesy p.47, p. 161
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306:(5–6). Springer Science and Business Media LLC: 279–291.
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Hofmann-Wellenhof and Moritz, Physical
Geodesy p. 163
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359:"GRAV-D Project Homepage- National Geodetic Survey"
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267:"Heights, the Geopotential, and Vertical Datums"
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79:Alternatives to orthometric height include
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128:. It can be related to orthometric height
94:Orthometric heights may be obtained from
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132:above the geoid by subtraction of the
16:Altitude above geoid or mean sea level
265:Jekeli, Christopher (November 2000).
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242:"National Geodetic Survey - Home"
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53:", along with other types of
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101:Helmert orthometric heights
64:datum is tied to a defined
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115:earth-centered coordinates
320:10.1007/s00190-003-0325-6
76:over thousands of miles.
117:, usually displayed as
60:In the US, the current
388:-related article is a
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51:height above sea level
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167:{\displaystyle H=h-N}
96:differential leveling
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312:2003JGeod..77..279H
185:has undertaken the
179:geoid determination
126:reference ellipsoid
300:Journal of Geodesy
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119:ellipsoidal height
113:measurements give
55:heights in Geodesy
45:that approximates
21:orthometric height
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134:geoid height
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433:Categories
284:2022-09-21
279:1811/78667
251:2020-09-07
209:References
124:above the
33:plumb line
31:along the
439:Surveying
328:0949-7714
159:−
66:elevation
27:) is the
336:54939075
197:See also
23:(symbol
444:Geodesy
386:geodesy
308:Bibcode
271:KB Home
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187:GRAV-D
105:NAVD88
62:NAVD88
41:, the
384:This
332:S2CID
38:geoid
390:stub
324:ISSN
177:The
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19:The
316:doi
275:hdl
183:NGS
111:GPS
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162:N
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25:H
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