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  1. North American Vertical Datum of 1988 - Wikipedia

    en.wikipedia.org/wiki/North_American_Vertical...

    The North American Vertical Datum of 1988 (NAVD 88) is the vertical datum for orthometric heights established for vertical control surveying in the United States of America based upon the General Adjustment of the North American Datum of 1988.

  2. North American Datum - Wikipedia

    en.wikipedia.org/wiki/North_American_Datum

    Vertical measurements, based on distances above or below Mean High Water (MHW), are calculated using the North American Vertical Datum of 1988 (NAVD 88). [1] NAD 83, along with NAVD 88, is set to be replaced with a new GPS - and gravimetric geoid model-based geometric reference frame and geopotential datum in 2022 .

  3. North American Vertical Datum of 1988 — Wikipedia Republished ...

    wiki2.org/en/North_American_Vertical_Datum_of_1988

    The North American Vertical Datum of 1988 (NAVD 88) is the vertical control datum of orthometric height established for vertical control surveying in the United States of America based upon the General Adjustment of the North American Datum of 1988.

  4. North American Vertical Datum of 1988 (NAVD 88) - Vertical ...

    www.ngs.noaa.gov/datums/vertical/north-american...

    Vertical Conversions (VDATUM) Download PC Software; GEOID18 Computation; GPS Toolbox; HTDP; VERTCON; Surveys. Active Geodetic Control (CORS) Adjust Leveling (LOCUS) Survey Mark Datasheets; Process GPS data (OPUS) Calibration Base Lines (CBLs) User-submitted Survey Projects (Bluebooking) GRAV-D; Geoid Slope Validation Survey (GSVS) Height ...

  5. North American Vertical Datum of 1988 - Wikipedia

    ro.wikipedia.org/wiki/North_American_Vertical...

    Datele verticalității în America de Nord (din 1988), acronim NAVD88 (în original, The North American Vertical Datum of 1988) este un set de măsurători de date geodezice referitoare la înălțimea ortometrică stabilită pentru a controla topografierea în Statele Unite ale Americii, bazată pe Ajustările generale ale datelor din America de nord din 1988 (în original, General ...

  6. North American Vertical Datum of 1988 - Infogalactic: the ...

    infogalactic.com/info/North_American_Vertical...

    The North American Vertical Datum of 1988 (NAVD 88) is the vertical control datum of orthometric height established for vertical control surveying in the United States of America based upon the General Adjustment of the North American Datum of 1988.

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  8. North American Vertical Datum of 1988 (NAVD 88) | Mass.gov

    www.mass.gov/service-details/north-american...

    The North American Vertical Datum of 1988 (NAVD 88) is the official vertical datum of the United States, having superseded the older National Geodetic Vertical Datum of 1929 (NGVD 29). Both NAVD 88 and NGVD 29 are geodetic datums, a reference surface of zero elevation to which heights are referred to over a large geographic extent.

  9. North_American_Vertical_Datum_of_1988 : definition of North ...

    dictionary.sensagent.com/North_American_Vertical_Datum...

    The North American Vertical Datum of 1988 (NAVD 88) is the vertical control datum established for vertical control surveying in the United States of America based upon the General Adjustment of the North American Datum of 1988.

  10. Results of the General Adjustment of the North American ...

    www.ngs.noaa.gov/PUBS_LIB/NAVD88/navd88report.htm

    North American Vertical Datum of 1988 Approximately 625,000 km of leveling have been added to the National Geodetic Reference System (NGRS) since NGVD 29 was created (figure 3). In the intervening years, discussions were held periodically to determine the proper time for the inevitable new general adjustment.

  11. Geodetic Datums: NAD 27, NAD 83 and WGS84 - GIS Geography

    gisgeography.com/geodetic-datums-nad27-nad83-wgs84
    • Introduction
    • Archaeology
    • Results
    • Nomenclature
    • Applications
    • Significance
    • Summary
    • Geology
    • Models
    • Details
    • Physical characteristics
    • History
    • Versions
    • Location
    • Performance

    Because the Earth is curved and in GIS we deal with flat map projections, we need to accommodate both the curved and flat views of the world. In surveying and geodesy, we accurately define these properties with geodetic datums. We begin modelling the Earth with a sphere or ellipsoid. Over time, surveyors have gathered a massive collection of surface measurements to more reliably estimate the ellipsoid.

    In order to create a geodetic datum, surveyors undertook a mammoth collection of monument locations in the late 1800s. Surveyors installed brass or aluminum disks at each reference location.

    From the unified network of survey monument, the result of triangulation was the North American Datum of 1927 (NAD 27). After, geodesists developed the more accurate NAD 83, which we still use today. NAD 27 and NAD 83 provide a frame of reference for latitude and longitude locations on Earth.

    NAD27 stands for North American Datum of 1927. NAD27 is the adjustment of long-baseline surveys. Overall, it established a network of standardized horizontal positions on North America. Most historical USGS topographic maps and projects by the US Army Corps of Engineers used NAD27 as a reference system.

    A horizontal datum provides a frame of reference as a basis for placing specific locations at specific points on the spheroid. Geodesists use a horizontal datum as the model to translate a spheroid / ellipsoid into locations on Earth with latitude and longitude lines. Geodetic datums form the basis of coordinates of all horizontal positions on Earth. All coordinates on Earth are referenced to a horizontal datum. The North American Datum of 1927 (NAD27) is one of the main three geodetic datums used in North America. NAD27 uses all horizontal geodetic surveys collected at this time using a least-square adjustment. This datum uses the Clarke Ellipsoid of 1866 with a fixed latitude and longitude at Meades Ranch, Kansas. (39°1326.686 north latitude, 98°3230.506 west longitude)

    Kansas was selected as a common reference point because it was near the center of the contiguous United States. The latitudes and longitudes of every other point in North America were based off its direction, angle and distance away from Meades Ranch. Any point with a latitude and longitude away from this reference point could be measured on the Clarke Ellipsoid of 1866.

    The North American Datum of 1983 (NAD 83) is a unified horizontal or geometric datum and successor to NAD27 providing a spatial reference for Canada and the United States.

    NAD83 corrects some of the distortions from NAD27 over distance by using a more sense set of positions from terrestrial and Doppler satellite data. NAD83 is a geocentric datum (referenced to the center of Earths mass) offset by about 2 meters. Even today, geodesists are continually improving horizontal geodetic datums.

    This has led to the development of global ellipsoid models such as WGS72, GRS80 and WGS84 (current). The World Geodetic System (WGS84) is the reference coordinate system used by the Global Positioning System.

    Never before have weve been able to estimate the ellipsoid with such precision because of the global set of measurements provided by GPS. It comprises of a reference ellipsoid, a standard coordinate system, altitude data and a geoid. Similar to NAD 83, it uses the Earths center mass as the coordinate origin. The error is believed to be less than 2 centimeters to the center mass.

    North American Datum of 1983 is based on the reference ellipsoid GRS80 which is physically larger than NAD27s Clarke ellipsoid. The GRS80 reference ellipsoid has a semi-major axis of 6,378,137.0 meters and a semi-minor axis of 6,356,752.3 meters. This compares to the Clarke ellipsoid with a semi-major axis of 6,378,206.4 m and semi-minor axis of 6,356,583.8 meters.

    The early attempts at measuring the ellipsoid used small amounts of data and did not represent the true shape of the Earth. In 1880, the Clarke ellipsoid was adopted as a basis for its triangulation computations. The first geodetic datum adopted for the United States was based on the Clarke ellipsoid with its starting point in Kansas known as Meades Ranch.

    Since 1986, geodesists have made several updates to NAD83. Actually, because of these changes, there are more than one version of NAD83. For example, the National Geodetic Survey has adjusted the NAD83 datum four times since the original geodetic datum estimation in 1986.

    The coordinates for benchmark datum points are typically different between geodetic datums. For example, the latitude and longitude location in a NAD27 datum differs from that same benchmark in NAD83 or WGS84. This difference is known as a datum shift.

    Depending on where you are in North America, NAD27 and NAD83 may differ in tens of meters for horizontal accuracy. The average correction between NAD27 and NAD83 is an average of 0.349 northward and 1.822 eastward.