hector_slam | hector_slam contains ROS packages related to performing SLAM | Robotics library

I have a relatively simple issue with the initialization of the robot pose in navigation stack. After doing a SLAM in the environment and saving the static map from map_server with desired resolution and size, and after finally making it available from static map server, I can not properly initialize my robot pose. Although, the initialization is possible with RVIZ (2D pose estimation option), it is inaccurate obviously since I am doing it by hand. This has a second draw back namely, when I am using a position (/move_base_trajectory topic) tracking instead of velocity tracking (/cmd_vel topic), there is an offset of the current position which I should manually compensate in my low-level controller. Is there any other proper (automatic) pose initialization approach?
PS: I am using Lidar /scan topic to feed costmap functionalities. I have also tested the initilization of the robot with hector_slam stack which pretty accurate however, with that I am getting a second map which interferes with the first one and pose association does not work. There should be a more proper approach I guess. I am loading my static map within the launch file: