proj4js：Proj4js is a JavaScript library to transform point coordinates from one coordinate system to another. 

openlayers是用proj4js做投影转换的吗？是用它来加载UTM切片的吗？

>>Supermap iClient for OpenLayers(using proj4js)：https://blog.csdn.net/supermapsupport/article/details/89306219

                                                            https://blog.csdn.net/supermapsupport/article/details/78952736