Spherical coordinates

The SphericalCoords ROS plugin provides services for the world's geographic origin and transformations between local Cartesian positions and latitude/longitude/altitude.

Start a configured world

ros2 launch posim_demos posim_world.launch.py \
  world_name:=posim_bimanual_example headless:=true

In a second sourced terminal:

ros2 service list -t
ros2 service call /gz/get_origin_spherical_coordinates \
  posim_interfaces/srv/GetOriginSphericalCoord '{}'

The example SDF sets latitude 35.074823° and longitude 129.084798°. Read the response for the actual running origin.

Service reference

Service suffix under `/gz/`	POSIM service type	Request
`get_origin_spherical_coordinates`	`GetOriginSphericalCoord`	Empty
`set_origin_spherical_coordinates`	`SetOriginSphericalCoord`	`latitude_deg`, `longitude_deg`, `altitude`
`transform_to_spherical_coordinates`	`TransformToSphericalCoord`	`input: {x, y, z}`
`transform_from_spherical_coordinates`	`TransformFromSphericalCoord`	`latitude_deg`, `longitude_deg`, `altitude`

Types live in posim_interfaces/srv. Angles are degrees; local coordinates and altitude are meters.

Convert a local position

ros2 service call /gz/transform_to_spherical_coordinates \
  posim_interfaces/srv/TransformToSphericalCoord \
  '{input: {x: 100.0, y: 200.0, z: 3.0}}'

The response contains latitude, longitude and altitude. Use those returned values with the inverse service and compare the resulting output to the original vector. This checks your configured origin and frame convention.

Change the origin

ros2 service call /gz/set_origin_spherical_coordinates \
  posim_interfaces/srv/SetOriginSphericalCoord \
  '{latitude_deg: 35.074823, longitude_deg: 129.084798, altitude: 0.0}'

Changing the origin updates how local positions map to latitude/longitude. Align terrain, world orientation, altitude reference and controllers with that coordinate system.

Gazebo's spherical-coordinate transformations are used internally. Keep the SDF's heading/orientation in mind rather than assuming every world has the same local axes.