def get_camera_locations(observations, all_camera_locations, exclude=False):
    """Return dict of all camera locations that appear in observations.
    
    observations: dict of observations. Probably all observations from one day.
    all_camera_locations: dict containing all camera locations across all days
    exclude: if True, exclude observations as marked in obs dict
    """
    camera_locations = {}
    for camera, obs in observations.items():
        if exclude:
            if 'exclude' in obs.keys():
                if obs['exclude']:
                    continue
        camera_locations[obs['camera']] = all_camera_locations[obs['camera']]
    return camera_locations