Well-Known Text (WKT) Representation of Spatial Reference Systems：顾名思义用众所周知的文字形式来描述看见坐标参照系统，它与EPSG（2005年已经换名）的坐标文字表述模型一致。
基础知识：坐标参照系有三种最常见的子类：地心坐标系(geocentric cs、GEOCCS)，地理坐标系(geographic cs、GEOGCS)，和投影坐标系(projected cs、PROJCS)
地理坐标系的格式：<geographic cs> = GEOGCS["<name>", <datum>, <prime meridian>, <angular unit>]
WGS1984的地理坐标系WKT形式：
GEOGCS["WGS 84",
DATUM["WGS_1984",
SPHEROID["WGS 84", 6378137, 298.257223563, AUTHORITY["EPSG", "7030"]],
AUTHORITY["EPSG", "6326"]],
PRIMEM["Greenwich", 0, AUTHORITY["EPSG", "8901"]],
UNIT["degree", 0.0174532925199433, AUTHORITY["EPSG", "9122"]],
AUTHORITY["EPSG", "4326"]]
投影坐标系的格式：<projected cs> = PROJCS["<name>", <geographic cs>, <projection>, {<parameter>,}* <linear unit>]
WGS1984地理坐标，统一横轴墨卡托(UTM)投影，中央经线117E的投影坐标系WKT形式：
PROJCS["WGS 84 / UTM zone 50N",
GEOGCS["WGS 84", DATUM["WGS_1984", SPHEROID["WGS 84", 6378137, 298.257223563, AUTHORITY["EPSG", "7030"]], AUTHORITY["EPSG", "6326"]], PRIMEM["Greenwich", 0, AUTHORITY["EPSG", "8901"]], UNIT["degree", 0.0174532925199433, AUTHORITY["EPSG", "9122"]], AUTHORITY["EPSG", "4326"]],
PROJECTION["Transverse_Mercator"],
PARAMETER["latitude_of_origin", 0],
PARAMETER["central_meridian", 117],
PARAMETER["scale_factor", 0.9996],
PARAMETER["false_easting", 500000],
PARAMETER["false_northing", 0],
UNIT["metre", 1, AUTHORITY["EPSG", "9001"]],
AUTHORITY["EPSG", "32650"]]
地心坐标系格式相似于地理坐标系：<geocentric cs> = GEOCCS["<name>", <datum>, <prime meridian>, <linear unit>]
