//import { Projection, addProjection } from 'ol/proj'
import proj4 from 'proj4';
import epsg from 'epsg';
import { register } from 'ol/proj/proj4';

function add_epsg() {
    var srsName = SRS;
    proj4.defs(srsName, epsg[srsName]);
    register(proj4);
}
add_epsg();

see

https://blog.csdn.net/qq_42248939/article/details/102687311
https://blog.csdn.net/freeland1/article/details/78579813

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