最新版的PROJ4已經把 TWD67，TWD97相關的 epsg 加入了。
下面把台灣常用的幾個epsg定義紀錄起來，很多時候會用到。
Google Map自訂的投影參數也順便記錄一下。
# WGS 84
<4326> +proj=longlat +ellps=WGS84 +datum=WGS84 +no_defs <>
# Spherical Mercator for Web GIS
<900913> +proj=merc +lon_0=0 +k=1 +x_0=0 +y_0=0 +ellps=WGS84 +datum=WGS84 +units=m +no_defs <>
# TWD97 / TM2 zone 119
<3825> +proj=tmerc +lat_0=0 +lon_0=119 +k=0.9999 +x_0=250000 +y_0=0 +ellps=GRS80 +towgs84=0,0,0,0,0,0,0 +units=m +no_defs <>
# TWD97 / TM2 zone 121
<3826> +proj=tmerc +lat_0=0 +lon_0=121 +k=0.9999 +x_0=250000 +y_0=0 +ellps=GRS80 +towgs84=0,0,0,0,0,0,0 +units=m +no_defs <>
# TWD67 / TM2 zone 119
<3827> +proj=tmerc +lat_0=0 +lon_0=119 +k=0.9999 +x_0=250000 +y_0=0 +ellps=aust_SA +units=m +towgs84=-752,-358,-179,-0.0000011698,0.0000018398,0.0000009822,0.00002329 +no_defs <>
# TWD67 / TM2 zone 121
<3828> +proj=tmerc +lat_0=0 +lon_0=121 +k=0.9999 +x_0=250000 +y_0=0 +ellps=aust_SA +units=m +towgs84=-752,-358,-179,-0.0000011698,0.0000018398,0.0000009822,0.00002329 +no_defs <>
2010/04/09 更新：
TWD67的坐標因為與WGS84使用不同的大地基準，所以補上towgs84的7參數轉換。
EPSG雖然納入TWD97,TWD67，但是TWD67若欠缺towgs84參數，坐標轉換的結果會差很多。
同時附上WKT格式的修正版：（官方網站能找到的都有缺漏）
3827=PROJCS["TWD67 / TM2 zone 119", GEOGCS["TWD67", DATUM["Taiwan Datum 1967", SPHEROID["GRS 1967 Modified", 6378160.0, 298.25, AUTHORITY["EPSG","7050"]], AUTHORITY["EPSG","1025"], TOWGS84[-752, -358, -179, -0.0000011698, 0.0000018398, 0.0000009822, 0.00002329]], PRIMEM["Greenwich", 0.0, AUTHORITY["EPSG","8901"]], UNIT["degree", 0.017453292519943295], AXIS["Geodetic longitude", EAST], AXIS["Geodetic latitude", NORTH], AUTHORITY["EPSG","3821"]], PROJECTION["Transverse Mercator", AUTHORITY["EPSG","9807"]], PARAMETER["central_meridian", 119.0], PARAMETER["latitude_of_origin", 0.0], PARAMETER["scale_factor", 0.9999], PARAMETER["false_easting", 250000.0], PARAMETER["false_northing", 0.0], UNIT["m", 1.0], AXIS["Easting", EAST], AXIS["Northing", NORTH], AUTHORITY["EPSG","3827"]]
3828=PROJCS["TWD67 / TM2 zone 121", GEOGCS["TWD67", DATUM["Taiwan Datum 1967", SPHEROID["GRS 1967 Modified", 6378160.0, 298.25, AUTHORITY["EPSG","7050"]], AUTHORITY["EPSG","1025"], TOWGS84[-752, -358, -179, -0.0000011698, 0.0000018398, 0.0000009822, 0.00002329]], PRIMEM["Greenwich", 0.0, AUTHORITY["EPSG","8901"]], UNIT["degree", 0.017453292519943295], AXIS["Geodetic longitude", EAST], AXIS["Geodetic latitude", NORTH], AUTHORITY["EPSG","3821"]], PROJECTION["Transverse Mercator", AUTHORITY["EPSG","9807"]], PARAMETER["central_meridian", 121.0], PARAMETER["latitude_of_origin", 0.0], PARAMETER["scale_factor", 0.9999], PARAMETER["false_easting", 250000.0], PARAMETER["false_northing", 0.0], UNIT["m", 1.0], AXIS["Easting", EAST], AXIS["Northing", NORTH], AUTHORITY["EPSG","3828"]]
