Change Gazebo origin coordinate

Hi, I need to integrate 2 robots in gazebo. The first one is an IRIS quadcopter with px4 in SITL. It works ok. It provide a topic (through mavros) called /mavros/global_position/local. It is the UTM coordinate of the robot. I have X=465710, Y=5249470 Then I have a second robot, a custom made model and controller and it does not have global coordinate available. But I have a /odom topic that provide position in gazebo coordinates (X=240, Y=100) I can insert both model in the same place using gazebo coordinates. How can I change gazebo origin to a certain UTM coordinate? I would like to gazebo think that it origin is X=465710, Y=5249470. The other option is to add a GPS to the second robot, but I think it could be harder. Thank