This example demonstrates the use of GeoJSON over Bing tiles. The
GeoJSON vector data is in geographic coordinates (EPSG:4326). The Bing
tiles are in a spherical mercator projection (EPSG:900913). By setting
projection property of the GeoJSON layer to the source
projection (EPSG:4326), the features are properly displayed over the
base layer. In general, the map projection determines how raster or
vector data is displayed. The layer projection corresponds to the
projection of the data source.
See the geojson-reprojected.js source for details on how this is done.