# Map Projection
Map projection is divided into GeoProjection (geometric projection) and LnglatProjection (longitude-latitude projection) depending on the map basemap.
Projection is mainly used to convert graphic geometry coordinates to longitude-latitude coordinates for rendering.
# Geometric Projection with CAD as Basemap
// Get map metadata
let metadata = await svc.metadata(mapid, "v1");
// Create a bounds object from the map bounds string
let mapBounds = vjmap.GeoBounds.fromString(metadata.bounds);
// Establish geometric projection coordinate system based on map bounds
let prj = new vjmap.GeoProjection(mapBounds);
// Get the center point geometry coordinates of the CAD map bounds
let center = mapBounds.center();
// Use the projection object to convert CAD geometry coordinates to longitude-latitude coordinates for rendering
let lngLat = prj.toLngLat(center);
// Create a marker based on these longitude-latitude coordinates and add it to the map
new vjmap.Marker().setLngLat(lngLat).addTo(map);
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# Longitude-Latitude Projection with Internet Map as Basemap
For longitude-latitude projection with internet maps as the basemap, since internet maps already use longitude-latitude coordinates, the longitude-latitude coordinates in the graphics are consistent with the longitude-latitude coordinates for rendering.
let prj = new vjmap.LnglatProjection();
let mapPoint = [106.31, 26.87];
let lngLat = prj.toLngLat(lngLat);
// lngLat output value is also [106.31, 26.87]
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