Knowledge

Earth's circumference

Source 📝

697:, whose job was to precisely measure the extent of the territory of Egypt for agricultural and taxation-related purposes. Furthermore, the fact that Eratosthenes' measure corresponds precisely to 252,000 stadia (according to Pliny) might be intentional, since it is a number that can be divided by all natural numbers from 1 to 10: some historians believe that Eratosthenes changed from the 250,000 value written by Cleomedes to this new value to simplify calculations; other historians of science, on the other side, believe that Eratosthenes introduced a new length unit based on the length of the meridian, as stated by Pliny, who writes about the stadion "according to Eratosthenes' ratio". 667: 663:. Depending on whether he used the "Olympic stade" (176.4 m) or the Italian stade (184.8 m), this would imply a circumference of 44,100 km (an error of 10%) or 46,100 km, an error of 15%. A value for the stadion of 157.7 metres has even been posited by L.V. Firsov, which would give an even better precision, but is plagued by calculation errors and false assumptions. In 2012, Anthony Abreu Mora repeated Eratosthenes's calculation with more accurate data; the result was 40,074 km, which is 66 km different (0.16%) from the currently accepted polar circumference. 848: 39: 655:, Egypt), the Sun was directly overhead, as the gnomon cast no shadow. Additionally, the shadow of someone looking down a deep well at that time in Syene blocked the reflection of the Sun on the water. Eratosthenes then measured the Sun's angle of elevation at noon in Alexandria by measuring the length of another gnomon's shadow on the ground. Using the length of the rod, and the length of the shadow, as the legs of a triangle, he calculated the angle of the sun's rays. This angle was about 7°, or 1/50th the circumference of a 540: 844:. They calculated the Earth's circumference to be within 15% of the modern value, and possibly much closer. How accurate it actually was is not known because of uncertainty in the conversion between the medieval Arabic units and modern units, but in any case, technical limitations of the methods and tools would not permit an accuracy better than about 5%. 752:
due north of Alexandria, and the difference in the star's elevation indicated the distance between the two locales was 1/48 of the circle, he multiplied 5,000 by 48 to arrive at a figure of 240,000 stadia for the circumference of the earth. It is generally thought that the stadion used by Posidonius
1056:
of the Earth, making the prototype about 0.02% shorter than the original proposed definition of the metre. Regardless, this length became the French standard and was progressively adopted by other countries in Europe. This is why the polar circumference of the Earth is actually 40,008 kilometres,
887:
formula. This was the earliest known use of dip angle and the earliest practical use of the law of sines. However, the method could not provide more accurate results than previous methods, due to technical limitations, and so al-Biruni accepted the value calculated the previous century by the
543:
Illustration showing a portion of the globe showing a part of the African continent. The sun beams shown as two rays hitting earth at Syene and Alexandria. Angle of sun beam and the gnomons (vertical sticks) is shown at Alexandria which allowed Eratosthenes' estimate of the circumference of
808:
intended by Aryabhata is in dispute. One careful reading gives an equivalent of 14,200 kilometres (8,800 mi), too large by 11%. Another gives 15,360 km (9,540 mi), too large by 20%. Yet another gives 13,440 km (8,350 mi), too large by 5%.
685:
Eratosthenes' method was actually more complicated, as stated by the same Cleomedes, whose purpose was to present a simplified version of the one described in Eratosthenes' book. Pliny, for example, has quoted a value of 252,000 stadia.
1594: 504:). The accuracy of measuring the circumference has improved since then, but the physical length of each unit of measure had remained close to what it was determined to be at the time, so the Earth's circumference is no longer a 1012:
of a circle – such that the polar circumference of the Earth would be exactly 21,600 miles. Gunter used Snellius's circumference to define a nautical mile as 6,080 feet, the length of one minute of arc at 48 degrees latitude.
753:
was almost exactly 1/10 of a modern statute mile. Thus Posidonius's measure of 240,000 stadia translates to 24,000 mi (39,000 km), not much short of the actual circumference of 24,901 mi (40,074 km).
765:
had added some 26,000 stadia to Eratosthenes's estimate. The smaller value offered by Strabo and the different lengths of Greek and Roman stadia have created a persistent confusion around Posidonius's result.
659:; assuming the Earth to be perfectly spherical, he concluded that its circumference was 50 times the known distance from Alexandria to Syene (5,000 stadia, a figure that was checked yearly), i.e. 250,000 908:, he chose to believe that the Earth's circumference was 25% smaller. If, instead, Columbus had accepted Eratosthenes's larger value, he would have known that the place where he made landfall was not 1453:) stated that if the distance is measured by some other number the result will be different, and using 3,750 instead of 5,000 produces this estimation: 3,750 x 48 = 180,000; see Fischer I., (1975), 556:, with an error on the real value between −2.4% and +0.8% (assuming a value for the stadion between 155 and 160 metres; the exact value of the stadion remains a subject of debate to this day; see 757:
noted that the distance between Rhodes and Alexandria is 3,750 stadia, and reported Posidonius's estimate of the Earth's circumference to be 180,000 stadia or 18,000 mi (29,000 km).
617:
He assumes the simplified (but inaccurate) hypothesis that Syene and Alexandria are on the same meridian. Syene was actually about 3 degrees of longitude east of Alexandria.
469:, by comparing altitudes of the mid-day sun at two places a known north–south distance apart. He achieved a great degree of precision in his computation. Treating the Earth as a 1398:"The Eratosthenes-Strabo Nile Map. Is It the Earliest Surviving Instance of Spherical Cartography? Did It Supply the 5000 Stades Arc for Eratosthenes' Experiment?" 496:), which is 21,600 partitions of the polar circumference (that is 60 minutes × 360 degrees). The polar circumference is also close to 40,000 kilometres because 1016:
In 1793, France defined the metre so as to make the polar circumference of the Earth 40,000 kilometres. In order to measure this distance accurately, the
1331: 761:
mentions Posidonius among his sources and—without naming him—reported his method for estimating the Earth's circumference. He noted, however, that
1052:
was based on these measurements, but it was later determined that its length was short by about 0.2 millimetres because of miscalculation of the
851:
Diagram showing how al-Biruni was able to calculate the Earth's circumference by measuring the dip of the horizon from a point at a known height.
398: 488:
in the eighteenth. Earth's polar circumference is very near to 21,600 nautical miles because the nautical mile was intended to express one
879:
top, which made it possible for it to be measured by a single person from a single location. From the top of the mountain, he sighted the
220: 863:(1037). In contrast to his predecessors, who measured the Earth's circumference by sighting the Sun simultaneously from two locations, 388: 356: 1029: 939: 473:, its circumference would be its single most important measurement. Earth deviates from spherical by about 0.3%, as characterized by 366: 956:
to determine latitude at sea. He reasoned that the lines of latitude could be used as the basis for a unit of measurement for
1730: 1709: 1688: 1665: 1632: 1270: 1204: 1144: 948:
assessed the circumference of the Earth at 24,630 Roman miles (24,024 statute miles). Around that time British mathematician
346: 1109: 1506: 1314: 326: 1520: 127: 1548: 626: 426: 1286: 925: 829: 480:
In modern times, Earth's circumference has been used to define fundamental units of measurement of length: the
212: 1747:
Carl Sagan demonstrates how Eratosthenes determined that the Earth was round and the approximate circumference
1609: 1037: 1564:
Behnaz Savizi (2007), "Applicable Problems in History of Mathematics: Practical Examples for the Classroom",
1021: 748:
between the latitude of the two locales is actually 5 degrees 14 minutes). Since he thought Rhodes was 5,000
670:
Measure of Earth's circumference according to Cleomedes' simplified version, based on the approximation that
228: 1332:"Eratosthenes and the Mystery of the Stades – How Long Is a Stade? – Mathematical Association of America" 770:
used Posidonius's lower value of 180,000 stades (about 33% too low) for the earth's circumference in his
1017: 614:
the Sun was directly overhead. Syene was actually north of the tropic by something less than a degree.
191: 1766: 1179: 904:
studied what Eratosthenes had written about the size of the Earth. Nevertheless, based on a map by
749: 500:
to be one ten millionth (i.e., a kilometre is one ten thousandth) of the arc from pole to equator (
489: 158: 931: 1573: 706: 296: 256: 1049: 567:, which has not been preserved; what has been preserved is the simplified version described by 276: 1194: 666: 1720: 1653: 1624:
The Measure of All Things: The Seven-Year Odyssey and Hidden Error That Transformed the World
953: 419: 336: 86: 1171: 883:
which, along with the mountain's height (which he determined beforehand), he applied to the
557: 901: 777: 571:
to popularise the discovery. Cleomedes invites his reader to consider two Egyptian cities,
497: 236: 186: 112: 1438: 8: 1455:
Another Look at Eratosthenes' and Posidonius' Determinations of the Earth's Circumference
1172: 945: 771: 521: 148: 96: 847: 465:
since ancient times. The first known scientific measurement and calculation was done by
1658:
Groundbreaking Scientific Experiments, Inventions, and Discoveries of the Ancient World
1486: 1417: 1397: 825: 517: 68: 38: 602:
He assumes the simplified (but inaccurate) hypothesis that Syene was precisely on the
548:
The measure of Earth's circumference is the most famous among the results obtained by
1726: 1705: 1684: 1661: 1628: 1544: 1421: 1266: 1200: 1140: 1081: 636: 455: 168: 153: 1450: 1025: 1771: 1577: 1409: 1360: 935: 675: 603: 529: 525: 501: 412: 163: 1699: 1677: 1622: 1470: 1113: 1071: 758: 1761: 977: 715: 660: 588: 553: 376: 143: 117: 1746: 880: 714:
calculated the Earth's circumference by reference to the position of the star
454:, it is 40,075.017 km (24,901.461 mi). Measured passing through the 1755: 1539:
Mercier, Raymond (1992). "Geodesy". In Harley, J.B.; Woodward, David (eds.).
1076: 949: 481: 443: 1581: 1066: 1045: 919: 889: 884: 868: 821: 745: 632: 587:
Cleomedes assumes that the distance between Syene and Alexandria was 5,000
549: 505: 493: 466: 101: 19: 1466: 1167: 1086: 794: 58: 1413: 1053: 905: 762: 727: 711: 679: 607: 572: 474: 462: 1679:
Circumference: Eratosthenes and the Ancient Quest to Measure the Globe
1349: 644: 1041: 913: 864: 856: 789: 719: 690: 622: 568: 137: 63: 1263:
Measuring the Universe: Cosmic Dimensions from Aristarchus to Halley
1507:"Journal of the Royal Asiatic Society of Great Britain and Ireland" 1364: 957: 876: 694: 611: 592: 316: 133: 122: 1491: 1032:
to attempt to accurately measure the distance between a belfry in
780:
in order to underestimate the distance to India as 70,000 stades.
1033: 833: 800: 767: 451: 196: 53: 30: 1287:"Astronomy 101 Specials: Eratosthenes and the Size of the Earth" 722:, Posidonius observed Canopus on but never above the horizon at 458:, the circumference is 40,007.863 km (24,859.734 mi). 818: 754: 723: 656: 640: 539: 470: 306: 266: 204: 1472:
Before Galileo: The Birth of Modern Science in Medieval Europe
1315:"How did Eratosthenes measure the circumference of the earth?" 960:
and proposed the nautical mile as one minute or one-sixtieth (
798:, in which he calculated the diameter of earth to be of 1,050 872: 841: 837: 671: 652: 648: 580: 576: 485: 447: 91: 1701:
Measuring the Earth: Eratosthenes and His Celestial Geometry
1596:
Measuring the Earth: Eratosthenes and His Celestial Geometry
1199:. Springer Science & Business Media. pp. 638–640. 909: 461:
Measurement of Earth's circumference has been important to
393: 286: 552:, who estimated that the meridian has a length of 252,000 920:
Historical use in the definition of units of measurement
563:
Eratosthenes described his technique in a book entitled
1192: 788:
Around AD 525, the Indian mathematician and astronomer
1610:
Why Nautical Mile and Knot Are The Units Used at Sea?
1543:. The University of Chicago Press. pp. 175–188. 643:
and under the previous assumptions, he knew that at
1457:, Ql. J. of the Royal Astron. Soc., Vol. 16, p.152. 1676: 855:A more convenient way to estimate was provided in 591:(a figure that was checked yearly by professional 926:History of the metre § Meridional definition 1753: 1485:Kak, Subhash (2010). "Aryabhata's Mathematics". 1433: 1431: 1186: 628:On the Circular Motions of the Celestial Bodies 1193:Shashi Shekhar; Hui Xiong (12 December 2007). 1563: 1265:. University of Chicago Press. pp. 4–5. 1162: 1160: 1158: 1156: 631:, around 240 BC, Eratosthenes calculated the 420: 18:For modern definitions and measurements, see 1652:Krebs, Robert E.; Krebs, Carolyn A. (2003). 1599:, p. 6 (Berkeley Heights, NJ: Enslow, 2010). 1541:The History of Cartography, Volume 2, Book 1 1428: 1139:. New York, NY: Watson-Guptill. p. 31. 1137:The Illustrated Encyclopedia of the Universe 952:improved navigational tools including a new 1048:through Dunkerque. The length of the first 871:calculations, based on the angle between a 1660:. Greenwood Publishing Group. p. 52. 1651: 1260: 1153: 932:Meridian arc § History of measurement 427: 413: 394:Spatial Reference System Identifier (SRID) 389:International Terrestrial Reference System 1614: 1566:Teaching Mathematics and Its Applications 1534: 1532: 1530: 1521:"The_Aryabhatiya_of_Aryabhata_Clark_1930" 1490: 1107: 1674: 1378: 1376: 1326: 1324: 900:1,700 years after Eratosthenes's death, 846: 665: 538: 1675:Nicastro, Nicholas (25 November 2008). 1654:"Calculating the Earth's Circumference" 1538: 1395: 1134: 940:Arc measurement of Delambre and Méchain 707:Posidonius § Earth's circumference 1754: 1718: 1557: 1527: 1342: 1719:Lowrie, William (20 September 2007). 1620: 1402:Archive for History of Exact Sciences 1373: 1321: 1309: 1307: 1166: 1108:Humerfelt, Sigurd (26 October 2010). 832:to measure the distance from Tadmur ( 812: 1697: 1484: 895: 484:in the seventeenth century and the 399:Universal Transverse Mercator (UTM) 361:European Terrestrial Ref. Sys. 1989 13: 1304: 1249:De nuptiis Philologiae et Mercurii 996:of a circle, one minute of arc is 639:. Using a vertical rod known as a 271:Ordnance Survey Great Britain 1936 237:Discrete Global Grid and Geocoding 128:Horizontal position representation 14: 1783: 1740: 1350:The Length of Eratosthenes' Stade 1219: 867:developed a new method of using 693:trips conducted by professional 689:The method was based on several 498:the metre was originally defined 187:Global Nav. Sat. Systems (GNSSs) 37: 1645: 1602: 1587: 1513: 1499: 1478: 1460: 1443: 1389: 744:degrees above the horizon (the 534: 351:N. American Vertical Datum 1988 1725:. Cambridge University Press. 1279: 1254: 1241: 1228: 1213: 1128: 1101: 1044:to estimate the length of the 980:of latitude. As one degree is 776:. This was the number used by 522:Spherical Earth § History 381:Internet link to a point 2010 311:Geodetic Reference System 1980 229:Quasi-Zenith Sat. Sys. (QZSS) 1: 1354:American Journal of Philology 1094: 1022:Jean Baptiste Joseph Delambre 700: 508:in metres or nautical miles. 371:Chinese obfuscated datum 2002 1178:. Berlin: Springer. p.  944:In 1617 the Dutch scientist 783: 678:and on the same meridian as 321:Geographic point coord. 1983 7: 1621:Alder, Ken (October 2003). 1261:Van Helden, Albert (1985). 1060: 936:Earth radius § History 730:he saw it ascend as far as 565:On the measure of the Earth 530:Meridian arc § History 526:Earth radius § History 281:Systema Koordinat 1942 goda 10: 1788: 1722:Fundamentals of Geophysics 1704:. Enslow Publishing, LLC. 1110:"How WGS 84 defines Earth" 1018:French Academy of Sciences 929: 923: 704: 647:on the summer solstice in 633:circumference of the Earth 515: 511: 341:World Geodetic System 1984 17: 1698:Gow, Mary (1 July 2009). 331:North American Datum 1983 301:South American Datum 1969 1396:Rawlins, Dennis (1983). 1222:The Forgotten Revolution 1174:The Forgotten Revolution 824:commissioned a group of 192:Global Pos. System (GPS) 159:Spatial reference system 1574:Oxford University Press 1368:(subscription required) 1683:. St. Martin's Press. 1627:. Simon and Schuster. 1386:, Book 2, Chapter 112. 1348:Donald Engels (1985). 852: 682: 545: 450:. Measured around the 1582:10.1093/teamat/hrl009 1135:Ridpath, Ian (2001). 930:Further information: 850: 669: 542: 440:Earth's circumference 87:Geographical distance 902:Christopher Columbus 804:. The length of the 778:Christopher Columbus 261:Sea Level Datum 1929 113:Geodetic coordinates 1291:www.eg.bucknell.edu 1247:Martianus Capella, 1196:Encyclopedia of GIS 1057:instead of 40,000. 1050:prototype metre bar 946:Willebrord Snellius 291:European Datum 1950 249:Standards (history) 149:Reference ellipsoid 97:Figure of the Earth 1414:10.1007/BF00348500 1384:Naturalis Historia 853: 826:Muslim astronomers 813:Islamic Golden Age 718:. As explained by 683: 546: 518:History of geodesy 169:Vertical positions 1732:978-1-139-46595-3 1711:978-0-7660-3120-3 1690:978-1-4299-5819-6 1667:978-0-313-31342-4 1634:978-0-7432-1676-0 1272:978-0-226-84882-2 1206:978-0-387-30858-6 1146:978-0-8230-2512-1 1082:Geographical mile 606:, saying that at 492:of latitude (see 437: 436: 385: 384: 164:Spatial relations 154:Satellite geodesy 109: 1779: 1736: 1715: 1694: 1682: 1671: 1639: 1638: 1618: 1612: 1608:Marine Insight, 1606: 1600: 1591: 1585: 1584: 1561: 1555: 1554: 1536: 1525: 1524: 1517: 1511: 1510: 1503: 1497: 1496: 1494: 1482: 1476: 1464: 1458: 1447: 1441: 1435: 1426: 1425: 1393: 1387: 1380: 1371: 1369: 1346: 1340: 1339: 1328: 1319: 1318: 1311: 1302: 1301: 1299: 1297: 1283: 1277: 1276: 1258: 1252: 1245: 1239: 1232: 1226: 1225: 1217: 1211: 1210: 1190: 1184: 1183: 1177: 1164: 1151: 1150: 1132: 1126: 1125: 1123: 1121: 1116:on 24 April 2011 1112:. Archived from 1105: 1011: 1009: 1008: 1005: 1002: 995: 993: 992: 989: 986: 975: 973: 972: 969: 966: 896:Columbus's error 743: 742: 738: 735: 676:Tropic of Cancer 604:Tropic of Cancer 502:quarter meridian 429: 422: 415: 253: 252: 232: 224: 216: 208: 200: 140: 99: 41: 27: 26: 1787: 1786: 1782: 1781: 1780: 1778: 1777: 1776: 1767:Units of length 1752: 1751: 1743: 1733: 1712: 1691: 1668: 1648: 1643: 1642: 1635: 1619: 1615: 1607: 1603: 1592: 1588: 1562: 1558: 1551: 1537: 1528: 1519: 1518: 1514: 1505: 1504: 1500: 1483: 1479: 1465: 1461: 1451:in Fragment 202 1448: 1444: 1436: 1429: 1394: 1390: 1381: 1374: 1367: 1347: 1343: 1330: 1329: 1322: 1313: 1312: 1305: 1295: 1293: 1285: 1284: 1280: 1273: 1259: 1255: 1246: 1242: 1233: 1229: 1218: 1214: 1207: 1191: 1187: 1165: 1154: 1147: 1133: 1129: 1119: 1117: 1106: 1102: 1097: 1072:Spherical Earth 1063: 1038:Montjuïc castle 1006: 1003: 1000: 999: 997: 990: 987: 984: 983: 981: 970: 967: 964: 963: 961: 942: 928: 922: 912:, but rather a 898: 861:Codex Masudicus 817:Around AD 830, 815: 786: 759:Pliny the Elder 740: 736: 733: 731: 709: 703: 637:Ptolemaic Egypt 537: 532: 514: 433: 404: 403: 250: 242: 241: 230: 222: 214: 206: 198: 182: 174: 173: 132: 82: 74: 73: 49: 23: 12: 11: 5: 1785: 1775: 1774: 1769: 1764: 1750: 1749: 1742: 1741:External links 1739: 1738: 1737: 1731: 1716: 1710: 1695: 1689: 1672: 1666: 1647: 1644: 1641: 1640: 1633: 1613: 1601: 1586: 1556: 1549: 1526: 1512: 1498: 1477: 1459: 1442: 1427: 1408:(3): 211–219. 1388: 1372: 1365:10.2307/295030 1359:(3): 298–311. 1341: 1320: 1317:. 3 July 2012. 1303: 1278: 1271: 1253: 1240: 1227: 1220:Russo, Lucio. 1212: 1205: 1185: 1152: 1145: 1127: 1099: 1098: 1096: 1093: 1092: 1091: 1090: 1089: 1084: 1074: 1069: 1062: 1059: 1026:Pierre Méchain 924:Main article: 921: 918: 897: 894: 814: 811: 785: 782: 705:Main article: 702: 699: 619: 618: 615: 610:on the summer 600: 597:mensores regii 536: 533: 513: 510: 435: 434: 432: 431: 424: 417: 409: 406: 405: 402: 401: 396: 391: 383: 382: 379: 373: 372: 369: 363: 362: 359: 353: 352: 349: 343: 342: 339: 333: 332: 329: 323: 322: 319: 313: 312: 309: 303: 302: 299: 293: 292: 289: 283: 282: 279: 273: 272: 269: 263: 262: 259: 251: 248: 247: 244: 243: 240: 239: 234: 226: 218: 210: 202: 194: 189: 183: 180: 179: 176: 175: 172: 171: 166: 161: 156: 151: 146: 144:Map projection 141: 130: 125: 120: 118:Geodetic datum 115: 110: 94: 89: 83: 80: 79: 76: 75: 72: 71: 66: 61: 56: 50: 47: 46: 43: 42: 34: 33: 9: 6: 4: 3: 2: 1784: 1773: 1770: 1768: 1765: 1763: 1760: 1759: 1757: 1748: 1745: 1744: 1734: 1728: 1724: 1723: 1717: 1713: 1707: 1703: 1702: 1696: 1692: 1686: 1681: 1680: 1673: 1669: 1663: 1659: 1655: 1650: 1649: 1636: 1630: 1626: 1625: 1617: 1611: 1605: 1598: 1597: 1590: 1583: 1579: 1575: 1571: 1567: 1560: 1552: 1550:9780226316352 1546: 1542: 1535: 1533: 1531: 1522: 1516: 1508: 1502: 1493: 1488: 1481: 1474: 1473: 1468: 1463: 1456: 1452: 1446: 1440: 1434: 1432: 1423: 1419: 1415: 1411: 1407: 1403: 1399: 1392: 1385: 1379: 1377: 1366: 1362: 1358: 1355: 1351: 1345: 1337: 1333: 1327: 1325: 1316: 1310: 1308: 1292: 1288: 1282: 1274: 1268: 1264: 1257: 1250: 1244: 1237: 1231: 1224:. p. 68. 1223: 1216: 1208: 1202: 1198: 1197: 1189: 1181: 1176: 1175: 1169: 1163: 1161: 1159: 1157: 1148: 1142: 1138: 1131: 1115: 1111: 1104: 1100: 1088: 1085: 1083: 1080: 1079: 1078: 1077:Nautical mile 1075: 1073: 1070: 1068: 1065: 1064: 1058: 1055: 1051: 1047: 1043: 1039: 1035: 1031: 1030:an expedition 1027: 1023: 1020:commissioned 1019: 1014: 979: 959: 955: 951: 950:Edmund Gunter 947: 941: 937: 933: 927: 917: 915: 911: 907: 903: 893: 891: 886: 882: 878: 874: 870: 869:trigonometric 866: 862: 858: 849: 845: 843: 839: 835: 831: 827: 823: 820: 810: 807: 803: 802: 797: 796: 791: 781: 779: 775: 774: 769: 764: 760: 756: 751: 747: 729: 725: 721: 717: 713: 708: 698: 696: 692: 687: 681: 677: 673: 668: 664: 662: 658: 654: 650: 646: 642: 638: 634: 630: 629: 624: 621:According to 616: 613: 609: 605: 601: 598: 594: 590: 586: 585: 584: 582: 578: 574: 570: 566: 561: 559: 555: 551: 541: 531: 527: 523: 519: 509: 507: 503: 499: 495: 491: 487: 483: 482:nautical mile 478: 476: 472: 468: 464: 459: 457: 453: 449: 445: 441: 430: 425: 423: 418: 416: 411: 410: 408: 407: 400: 397: 395: 392: 390: 387: 386: 380: 378: 375: 374: 370: 368: 365: 364: 360: 358: 355: 354: 350: 348: 345: 344: 340: 338: 335: 334: 330: 328: 325: 324: 320: 318: 315: 314: 310: 308: 305: 304: 300: 298: 295: 294: 290: 288: 285: 284: 280: 278: 275: 274: 270: 268: 265: 264: 260: 258: 255: 254: 246: 245: 238: 235: 233: 227: 225: 219: 217: 211: 209: 205:BeiDou (BDS) 203: 201: 195: 193: 190: 188: 185: 184: 178: 177: 170: 167: 165: 162: 160: 157: 155: 152: 150: 147: 145: 142: 139: 135: 131: 129: 126: 124: 121: 119: 116: 114: 111: 107: 106:circumference 103: 98: 95: 93: 90: 88: 85: 84: 78: 77: 70: 67: 65: 62: 60: 57: 55: 52: 51: 45: 44: 40: 36: 35: 32: 29: 28: 25: 21: 16: 1721: 1700: 1678: 1657: 1646:Bibliography 1623: 1616: 1604: 1595: 1589: 1569: 1565: 1559: 1540: 1515: 1501: 1480: 1471: 1462: 1454: 1445: 1439:fragment 202 1437:Posidonius, 1405: 1401: 1391: 1383: 1356: 1353: 1344: 1335: 1294:. Retrieved 1290: 1281: 1262: 1256: 1248: 1243: 1238:, i.7.49–52. 1235: 1230: 1221: 1215: 1195: 1188: 1173: 1168:Russo, Lucio 1136: 1130: 1118:. Retrieved 1114:the original 1103: 1067:Earth radius 1046:meridian arc 1015: 943: 899: 892:expedition. 885:law of sines 860: 854: 840:, in modern 830:Al-Khwarizmi 816: 805: 799: 793: 787: 772: 746:meridian arc 710: 688: 684: 627: 620: 596: 564: 562: 550:Eratosthenes 547: 535:Eratosthenes 506:round number 494:meridian arc 479: 467:Eratosthenes 460: 439: 438: 181:Technologies 136: / 105: 48:Fundamentals 24: 20:Earth radius 15: 1593:Gow, Mary. 1467:John Freely 1449:Cleomedes ( 1336:www.maa.org 1296:19 December 1234:Cleomedes, 1087:Arabic mile 795:Aryabhatiya 726:, while at 59:Geodynamics 1756:Categories 1095:References 1054:flattening 906:Toscanelli 763:Hipparchus 728:Alexandria 712:Posidonius 701:Posidonius 680:Alexandria 674:is on the 645:local noon 608:local noon 573:Alexandria 516:See also: 475:flattening 463:navigation 1576:: 45–50, 1492:1002.3409 1422:118004246 1251:, VI.598. 1236:Caelestia 1042:Barcelona 1034:Dunkerque 976:) of one 914:New World 890:al-Ma'mun 881:dip angle 865:al-Biruni 857:Al-Biruni 822:Al-Ma'mun 790:Aryabhata 784:Aryabhata 773:Geography 720:Cleomedes 695:bematists 691:surveying 623:Cleomedes 593:bematists 569:Cleomedes 138:Longitude 64:Geomatics 1170:(2004). 1120:29 April 1061:See also 1028:to lead 958:distance 954:quadrant 877:mountain 651:(modern 612:solstice 579:(modern 444:distance 317:ISO 6709 215:(Europe) 213:Galileo 199:(Russia) 197:GLONASS 134:Latitude 123:Geodesic 81:Concepts 1772:Geodesy 1509:. 1907. 1382:Pliny, 1010:⁠ 998:⁠ 994:⁠ 982:⁠ 974:⁠ 962:⁠ 834:Palmyra 828:led by 801:yojanas 768:Ptolemy 739:⁄ 716:Canopus 558:stadion 512:History 452:equator 446:around 442:is the 377:Geo URI 347:NAVD 88 257:NGVD 29 231:(Japan) 223:(India) 207:(China) 69:History 54:Geodesy 31:Geodesy 1729:  1708:  1687:  1664:  1631:  1547:  1475:(2012) 1420:  1269:  1203:  1143:  978:degree 938:, and 819:Caliph 806:yojana 792:wrote 755:Strabo 750:stadia 724:Rhodes 661:stadia 657:circle 641:gnomon 589:stadia 581:Assuan 554:stadia 544:Earth. 528:, and 490:minute 471:sphere 367:GCJ-02 357:ETRS89 337:WGS 84 327:NAD 83 307:GRS 80 267:OSGB36 221:NAVIC 102:radius 1762:Earth 1572:(1), 1487:arXiv 1418:S2CID 1182:–277. 1007:21600 873:plain 842:Syria 838:Raqqa 836:) to 672:Syene 653:Aswan 649:Syene 577:Syene 486:metre 456:poles 448:Earth 297:SAD69 277:SK-42 92:Geoid 1727:ISBN 1706:ISBN 1685:ISBN 1662:ISBN 1629:ISBN 1545:ISBN 1298:2017 1267:ISBN 1201:ISBN 1141:ISBN 1122:2011 1036:and 1024:and 910:Asia 875:and 575:and 287:ED50 104:and 1578:doi 1410:doi 1361:doi 1357:106 1180:273 1040:in 991:360 859:'s 635:in 583:): 560:). 1758:: 1656:. 1570:26 1568:, 1529:^ 1469:, 1430:^ 1416:. 1406:26 1404:. 1400:. 1375:^ 1352:. 1334:. 1323:^ 1306:^ 1289:. 1155:^ 971:60 934:, 916:. 625:' 599:). 595:, 524:, 520:, 477:. 1735:. 1714:. 1693:. 1670:. 1637:. 1580:: 1553:. 1523:. 1495:. 1489:: 1424:. 1412:: 1370:. 1363:: 1338:. 1300:. 1275:. 1209:. 1149:. 1124:. 1004:/ 1001:1 988:/ 985:1 968:/ 965:1 741:2 737:1 734:+ 732:7 428:e 421:t 414:v 108:) 100:( 22:.

Index

Earth radius
Geodesy

Geodesy
Geodynamics
Geomatics
History
Geographical distance
Geoid
Figure of the Earth
radius
circumference
Geodetic coordinates
Geodetic datum
Geodesic
Horizontal position representation
Latitude
Longitude
Map projection
Reference ellipsoid
Satellite geodesy
Spatial reference system
Spatial relations
Vertical positions
Global Nav. Sat. Systems (GNSSs)
Global Pos. System (GPS)
GLONASS (Russia)
BeiDou (BDS) (China)
Galileo (Europe)
NAVIC (India)

Text is available under the Creative Commons Attribution-ShareAlike License. Additional terms may apply.