POSC Specifications
Version 3.0
Epicentre Standard Values
ellipsoid

ellipsoid

Standard Instance Values

Alias values exist. Go to the alias file.

identifier description naming _system inverse _flattening semimajor _axis semiminor _axis source _reference source _content source version status
    naming _system .identifier             ref _version .identifier  
Airy 1830 Original definition is a=20923713 and b=20853810 feet of 1796. For the 1936 retriangulation OSGB defines the relationship of feet of 1796 to the International metre through log(1.48401603) exactly [=0.3048007491...]. 1/f is given to 7 decimal places. EPSG name 299.3249646 6377563.396 m   Ordnance Survey of Great Britain. EPSG POSC epicentre 2.1 current
Airy Modified 1849 OSGB Airy 1830 figure rescaled by 1.000035 to best fit the primary triangulation of Ireland. EPSG name 299.3249646 6377340.189 m     EPSG POSC epicentre 2.1 current
Australian National Spheroid Based on the GRS 1967 figure but with 1/f taken to 2 decimal places exactly. EPSG name 298.25 6378160 m   Australian Map Grid Technical Manual; National Mapping Council of Australia Special Publication #7; 1972 EPSG POSC epicentre 2.1 current
Bessel 1841 Original Bessel definition is a=3272077.14 and b=3261139.33 toise. This used a weighted mean of values from several authors but did not account for differences in the length of the various toise: the Bessel toise is therefore of uncertain length. EPSG name 299.1528128 6377397.155 m   US Army Map Service Technical Manual; 1943. EPSG POSC epicentre 2.1 current
Bessel Modified Used in Norway and also in Sweden with a 1mm increase in semi-major axis. EPSG name 299.1528128 6377492.018 m     EPSG POSC epicentre 2.1 current
Bessel Namibia a = 6377397.155 German legal metres. This is the same value as the Bessel 1841 figure (code 7004) but in different units. Used in Namibia. EPSG name 299.1528128 6377483.865 m     EPSG POSC epicentre 2.1 current
Clarke 1858 Clarke's 1858/II solution. Derived parameters: a = 6378293.645m using his 1865 ratio of 0.304797265 feet per metre; 1/f = 294.26068. In historic usage in Australia 1/f taken to two decimal places (294.26 exactly); elsewhere a and b used to derive 1/f. EPSG name   20926348 ftCla 20855233 ftCla Ellipsoidisch Parameter der Erdfigur (1800-1950) by Georg Strasser. EPSG POSC epicentre 2.1 current
Clarke 1866 Original definition a=20926062 and b=20855121 (British) feet. Uses Clarke's 1865 inch-metre ratio of 39.370432 to obtain metres. (Metric value then converted to US survey feet for use in the United States using 39.37 exactly giving a=20925832.16 ft US). EPSG name   6378206.4 m 6356583.8 m US Army Map Service Technical Manual No. 7; 1943. EPSG POSC epicentre 2.1 current
Clarke 1866 Michigan Used for Michigan NAD27 State Plane zones. Radius = ellipsoid radius + 800 feet; this approximates the average elevation of the state. Derived parameter: 1/f = 294.97870 EPSG name   20926631.53 ftUS 20855688.67 ftUS USGS Professional Paper #1395. EPSG POSC epicentre 2.1 current
Clarke 1880 (Benoit) Adopts Clarke's values for a and b. Uses Benoit's 1895 ratio of 0.9143992 metres per yard to convert to metres. EPSG name   6378300.789 m 6356566.435 m   EPSG POSC epicentre 2.1 current
Clarke 1880 (IGN) Adopts Clarke's values for a and b using his 1865 ratio of 39.370432 inches per metre to convert axes to metres. EPSG name   6378249.2 m 6356515 m   EPSG POSC epicentre 2.2.2 current
Clarke 1880 (RGS) Adopts Clarke's values for a and 1/f. Adopts his 1865 ratio of 39.370432 inches per metre to convert semi-major axis to metres. Also known as Clarke Modified 1880. EPSG name 293.465 6378249.145 m   Empire Survey Review #32; 1939. EPSG POSC epicentre 2.1 current
Clarke 1880 (Arc) Adopts Clarke's value for a with derived 1/f. Uses his 1865 ratio of 39.370432 inch per metre to convert semi-major axis to metres. EPSG name 293.4663077 6378249.145 m     EPSG POSC epicentre 2.1 current
Clarke 1880 (SGA 1922) Used in Old French Triangulation (ATF). Uses Clarke's 1865 inch-metre ratio of 39.370432 to convert axes to metres. EPSG name 293.46598 6378249.2 m     EPSG POSC epicentre 2.1 current
Everest 1830 (1937 Adjustment) Used for the 1937 readjustment of Indian triangulation. Clarke's 1865 Indian-British foot ratio (0.99999566) and Benoit's 1898 British inch-metre ratio (39.370113) rounded as 0.30479841 exactly and applied to Everest's 1830 definition taken as a and 1/f EPSG name 300.8017 6377276.345 m   Survey of India professional paper #28; 1939 EPSG POSC epicentre 2.1 current
Everest 1830 (1967 Definition) Adopted 1967 for use in East Malaysia. Applies Sears 1922 inch-metre ratio of 39.370147 to Everest 1830 original definition of a and 1/f but with a taken to be in British rather than Indian feet. EPSG name 300.8017 6377298.556 m     EPSG POSC epicentre 2.1 current
Everest 1830 Modified Adopted 1967 for use in West Malaysia. Applies Benoit 1898 inch-metre ratio of 39.370113 to Everest 1830 original definition of a and 1/f but with a taken to be in British rather than Indian feet. EPSG name 300.8017 6377304.063 m     EPSG POSC epicentre 2.1 current
GRS 1980 Adopted by IUGG 1979 Canberra. Inverse flattening is derived from geocentric gravitational constant GM = 3986005e8 m*m*m/s/s; dynamic form factor J2 = 108263e8 and Earth's angular velocity = 7292115e-11 rad/s. EPSG name 298.2572221 6378137 m   Geodetic Reference System 1980 by H. Moritz; Bulletin Geodesique EPSG POSC epicentre 2.1 current

ellipsoid

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identifier description naming _system inverse _flattening semimajor _axis semiminor _axis source _reference source _content source version status
Helmert 1906 Helmert 1906/III solution. EPSG name 298.3 6378200 m   Ellipsoidisch Parameter der Erdfigur (1800-1950) by Georg Strasser EPSG POSC epicentre 2.1 current
Indonesian National Spheroid Based on the GRS 1967 figure but with 1/f taken to 3 decimal places exactly. EPSG name 298.247 6378160 m   Rais paper. EPSG POSC epicentre 2.1 current
International 1924 Adopted by IUGG 1924 in Madrid. Based on Hayford 1909/1910 figures. EPSG name 297 6378388 m     EPSG POSC epicentre 2.1 current
Krassowsky 1940   EPSG name 298.3 6378245 m     EPSG POSC epicentre 2.1 current
NWL 9D Used by Transit Precise Ephemeris between October 1971 and January 1987. EPSG name 298.25 6378145 m     EPSG POSC epicentre 2.1 current
Plessis 1817 Rescaling of Delambre 1810 figure (a=6376985 m) to make meridional arc from equator to pole equal to 10000000 metres exactly. (Ref: Strasser). EPSG name 308.64 6376523 m   IGN Paris Constants d'Ellipsoides February 1972. EPSG POSC epicentre 2.1 current
Struve 1860 Original definition of semi-major axis given as 3272539 toise. In Ellipsoidisch Parameter der Erdfigur (1800-1950) , Strasser suggests a conversion factor of 1.94903631 which gives a=6378297.337 metres. EPSG name 294.73 6378298.3 m   Geodesia y Cartografia Matematica by Fernando Martin Asin; ISBN 84-398-0248-X. EPSG POSC epicentre 2.1 current
War Office   EPSG name 296 6378300.583 m     EPSG POSC epicentre 2.1 current
WGS 84 Inverse flattening derived from four defining parameters (semi-major axis; C20 = -484.16685*10e-6; earth's angular velocity w = 7292115e11 rad/sec; gravitational constant GM = 3986005e8 m*m*m/s/s). EPSG name 298.2572236 6378137 m   DMA Technical Manual 8350.2-B EPSG POSC epicentre 2.1 current
GEM 10C Used for GEM 10C Gravity Potential Model. EPSG name 298.2572236 6378137 m     EPSG POSC epicentre 2.1 current
OSU86F Used for OSU86 gravity potential (geoidal) model. EPSG name 298.2572236 6378136.2 m     EPSG POSC epicentre 2.1 current
OSU91A Used for OSU91 gravity potential (geoidal) model. EPSG name 298.2572236 6378136.3 m     EPSG POSC epicentre 2.1 current
Clarke 1880 Clarke gave a and b and also 1/f=293.465 (to 3 decimal places). 1/f derived from a and b = 293.4663077. EPSG name 293.465 20926202 ftCla 20854895 ftCla Ellipsoidisch Parameter der Erdfigur (1800-1950) by Georg Strasser. EPSG POSC epicentre 2.1 current
Sphere Authalic sphere. 1/f is infinite. EPSG name   6371000 m 6371000 m   EPSG POSC epicentre 2.1 current
GRS 1967 Adopted by IUGG 1967 Lucerne. Inverse flattening given is derived from geocentric gravitational constant (GM)= 398603e9 m*m*m/s/s; dynamic form factor (J2) = 0.0010827 and Earth's angular velocity w = 7.2921151467e-5 rad/s. EPSG name 298.2471674 6378160 m   Geodetic Reference System 1967; International Association of Geodesy special publication number 3; August 1971. EPSG POSC epicentre 3.0 current
Average Terrestrial System 1977   EPSG name 298.257 6378135 m   New Brunswick Geographic Information Corporation land and water information standards manual EPSG POSC epicentre 2.1 current
Everest (1830 Definition) Everest gave a and b to 2 decimal places and also 1/f=300.8017 (to 4 decimal places). EPSG name 300.8017 20922931.8 ftInd 20853374.58 ftInd Ellipsoidisch Parameter der Erdfigur (1800-1950) by Georg Strasser EPSG POSC epicentre 3.0 current
WGS 72   EPSG name 298.26 6378135 m     EPSG POSC epicentre 3.0 current
Everest 1830 (1962 Definition) Used by Pakistan since metrication. Clarke's 1865 Indian foot-British foot ratio (0.99999566) and his 1865 British inch-metre ratio (39.369971) rounded with slight error as 1 Ind ft = 0.3047995m exactly and applied to Everest's 1830 definition of a & b. EPSG name 300.8017255 6377301.243 m     EPSG POSC epicentre 3.0 current
Everest 1830 (1975 Definition) Used by India since metrication. Clarke's 1865 Indian foot-British foot ratio (0.99999566) and his 1865 British inch-metre ratio (39.369971) rounded as 1 Ind ft = 0.3047995m exactly applied to Everest's 1830 original definition taken as a and b. EPSG name 300.8017255 6377299.151 m     EPSG POSC epicentre 2.1 current

ellipsoid

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identifier description naming _system inverse _flattening semimajor _axis semiminor _axis source _reference source _content source version status
Unknown Use this if the ellipsoid is unknown. The values for the semi-major axis and the semi-minor axis are meaningless. POSC basic   1.0 m 1.0 m   EPSG POSC epicentre 2.1 current

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