Cesium 加载 GeoJson 报错 RuntimeError message: “Unknown crs name: urn:ogc:def:crs:EPSG::3857

 加入以下代码拓展一下Cesium.GeoJsonDataSource.crsNames即可

 来源：https://github.com/hslayers/hslayers-ng/blob/efa5df4ddaf0860cef106b8383cd7f18d8ec5c30/components/hscesium/hscesium-layers.service.ts

// 解决"RuntimeError", message: "Unknown crs name: urn:ogc:def:crs:EPSG::3857"
import {default as proj4} from 'proj4';


              Cesium.GeoJsonDataSource.crsNames[
                "urn:ogc:def:crs:EPSG::3857"
              ] = Cesium.GeoJsonDataSource.crsNames["EPSG:3857"] = function(
                coordinates
              ) {
                const firstProjection =
                  'PROJCS["WGS 84 / Pseudo-Mercator",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["Mercator_1SP"],PARAMETER["central_meridian",0],PARAMETER["scale_factor",1],PARAMETER["false_easting",0],PARAMETER["false_northing",0],UNIT["metre",1,AUTHORITY["EPSG","9001"]],AXIS["X",EAST],AXIS["Y",NORTH],EXTENSION["PROJ4","+proj=merc +a=6378137 +b=6378137 +lat_ts=0.0 +lon_0=0.0 +x_0=0.0 +y_0=0 +k=1.0 +units=m [email protected] +wktext  +no_defs"],AUTHORITY["EPSG","3857"]]';
                const secondProjection =
                  '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"]]';

                const xa = coordinates[0];
                const ya = coordinates[1];

                const newCoordinates = proj4(
                  firstProjection,
                  secondProjection,
                  [xa, ya]
                );
                return Cesium.Cartesian3.fromDegrees(
                  newCoordinates[0],
                  newCoordinates[1],
                  0
                );
              };