Mavros move drone, no gps

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Here am I again...

I have been trying and trying but I can't seem to get the hang of it... I'm trying to move a drone to a certain location. I have the distances, which get updated whit a frequency of 30Hz, to the certain location in m in the x- and y-axis. With PID-controllers I convert the distances to velocities. Those velocities are not to move the drone in North, East direction but in forward, left, right direction. I'm trying to send those velocities to my drone using the mavros/setpoint_velocity/cmd_vel topic. But I'm not really sure if this is the correct one. Something extra: I can't use a gps.

Does someone can help me with this?

Thanks!