Updated tutorial

Signed-off-by: Aditya <aditya050995@gmail.com>

tutorials/spherical_coordinates.md

@@ -3,11 +3,13 @@
 Gazebo supports the use of real world latitude and longitude coordinates in its
 simulations using the
 [WGS84](https://en.wikipedia.org/wiki/World_Geodetic_System#1984_version)
-geodetic system.
+geodetic system for Earth,
+[MOON_SCS](https://en.wikipedia.org/wiki/Selenographic_coordinate_system)
+for the Moon, and analogous latitues and longitudes for custom surfaces.
 
 Gazebo Sim's simulation is always performed in Cartesian coordinates (good old XYZ).
 Therefore, in order to use spherical coordinates, it's necessary to project
-coordinates expressed in the `WGS84` frame to Cartesian and back.
+coordinates expressed in the appropriate surface frame to Cartesian and back.
 
 This tutorial will go over how to:
 
@@ -53,8 +55,11 @@ For example:
 </spherical_coordinates>
 ```
 
-At the moment, the only surface model supported is WGS84 and the only world
-frame orientation is ENU.
+Gazebo currently supports 3 surfaces models: ``WGS84``, ``MOON_SCS``, and
+``CUSTOM_SURFACE``. Custom sufaces require additional ``<surface_axis_polar>``
+and ``<surface_axis_equatorial>`` tags to fully specify the model.
+
+The only world frame currently supported is ENU.
 
 Try out an example world that ships with Gazebo and has the coordinates above
 as follows: