Problem of convert from global coordinate to lat/lon coordinate

smallbot · August 6, 2024, 2:48am

Hi,

I have some questions about the conversion from global coordinates to latitude and longitude coordinates.

I want to convert the nuscenes map from the global coordinate system to the latitude and longitude coordinate system, and then align it with the openstreetmap map.

I found a function related to coordinate conversion from the code of nuscenes-devkit:

github.com

nutonomy/nuscenes-devkit/blob/master/python-sdk/nuscenes/scripts/export_poses.py#L76


        math.sin(lat) * math.cos(angular_distance) + 
        math.cos(lat) * math.sin(angular_distance) * math.cos(bearing)
    )
    target_lon = lon + math.atan2(
        math.sin(bearing) * math.sin(angular_distance) * math.cos(lat),
        math.cos(angular_distance) - math.sin(lat) * math.sin(target_lat)
    )
    return math.degrees(target_lat), math.degrees(target_lon)




def derive_latlon(location: str, poses: List[Dict[str, float]]) -> List[Dict[str, float]]:
    """
    For each pose value, extract its respective lat/lon coordinate and timestamp.
    
    This makes the following two assumptions in order to work:
        1. The reference coordinate for each map is in the south-western corner.
        2. The origin of the global poses is also in the south-western corner (and identical to 1).


    :param location: The name of the map the poses correspond to, ie: 'boston-seaport'.
    :param poses: All nuScenes egopose dictionaries of a scene.
    :return: A list of dicts (lat/lon coordinates and timestamps) for each pose.

I used this code to extract the lane polygons from the nuscenes map and visualized them in qgis.
At first glance, the lane polygons of the nuscenes map and the google satellite image are aligned well, but when I tried to display the nuplan map in qgis, I found that there was a mismatch between the nuplan map and the nuscenes map.
Because the nuplan map is in gpkg format, which comes with the definition of the coordinate system, I guess the nuplan map is correct. If my guess is correct, then the function that converts the nuscenes map from global coordinates to latitude and longitude coordinates is wrong?

Below is the map of the Singapore-OneNorth and Boston-Seaport.
The green one is from Nuscenes and the red one is from Nuplan.
The top row is Singapore-OneNorth, the bottom row is Boston-Seaport.
The left column is a global view, and the middle and right columns are local enlargements.
It seems that the map of Nuscenes is smaller than that of Nuplan.

Thank you very much for reading, looking forward to your reply.