Question

我正在寻找一种方法（javascript）（ol3的外部或内部部分），它可以将投影WKT解析为其proj4文本并创建投影。

 <SRS>PROJCS["GDA94 / MGA zone 53",GEOGCS["GDA94",DATUM["Geocentric_Datum_of_Australia_1994",SPHEROID["GRS 1980",6378137,298.2572221010002,AUTHORITY["EPSG","7019"]],AUTHORITY["EPSG","6283"]],PRIMEM["Greenwich",0],UNIT["degree",0.0174532925199433],AUTHORITY["EPSG","4283"]],PROJECTION["Transverse_Mercator"],PARAMETER["latitude_of_origin",0],PARAMETER["central_meridian",135],PARAMETER["scale_factor",0.9996],PARAMETER["false_easting",500000],PARAMETER["false_northing",10000000],UNIT["metre",1,AUTHORITY["EPSG","9001"]],AUTHORITY["EPSG","28353"]]</SRS>

上面显示了包含SRS的XML元素的示例。

我发现如果我可以将其转换为proj4文本。然后我可以这样添加它作为投影：

proj4.defs("EPSG:28353", "+proj=utm +zone=53 +south +ellps=GRS80 +towgs84=0,0,0,0,0,0,0 +units=m +no_defs");

var def = proj4.defs(grid.srs);
var units = def.units;
        var proj = new ol.proj.Projection({
            code: grid.srs,
            units: units,
            axisOrientation: def.axis
        });
        proj.setExtent(/*...*/);
        ol.proj.addProjection(proj);
        var proj4Transform1 = proj4('EPSG:3857', grid.srs);
        ol.proj.addCoordinateTransforms(ol.proj.get('EPSG:3857'), proj,
            proj4Transform1.forward, proj4Transform1.inverse);
        var proj4Transform2 = proj4('EPSG:4326', grid.srs);
        ol.proj.addCoordinateTransforms(ol.proj.get('EPSG:4326'), proj,
            proj4Transform2.forward, proj4Transform2.inverse);

是否有可能在WKT中找到投影的延伸，还是应该在外部查看？

Answer 1

proj4js也支持WKT字符串。您可以使用相同的语法直接在proj4js中抛出您拥有的内容（不包括<SRS>标记）：

proj4.defs("EPSG:28353", "PROJCS["GDA94 / MGA zone 53",GEOGCS["GDA94",DATUM["Geocentric_Datum_of_Australia_1994",SPHEROID["GRS 1980",6378137,298.2572221010002,AUTHORITY["EPSG","7019"]],AUTHORITY["EPSG","6283"]],PRIMEM["Greenwich",0],UNIT["degree",0.0174532925199433],AUTHORITY["EPSG","4283"]],PROJECTION["Transverse_Mercator"],PARAMETER["latitude_of_origin",0],PARAMETER["central_meridian",135],PARAMETER["scale_factor",0.9996],PARAMETER["false_easting",500000],PARAMETER["false_northing",10000000],UNIT["metre",1,AUTHORITY["EPSG","9001"]],AUTHORITY["EPSG","28353"]]");

使用proj4.defs()定义投影后，它将立即在OpenLayers 3中可用，并且所有转换都将被注册。因此除非您想设置其他选项，例如您的情况下的投影范围，否则proj4.defs()行就是您所需要的。有两种选择：1）全局：

ol.proj.get('EPSG:28353').setExtent(*/ ... */);

或2）仅适用于您用于的一个ol.proj.Projection实例配置您的ol.View：

var projection = new ol.proj.Projection({
  code: 'EPSG:28353',
  extent: /* ... */
});

在OpenLayers中解析投影WKT 3

1 个答案: