I've followed these two tutorials to import heightmaps into Gazebo (9.12.0):

http://gazebosim.org/tutorials/?tut=dem

https://github.com/as4sr/general_info/wiki/Creating-heightmaps-for-gazebo

I am able to complete the tutorials, but when I try to use my own .tif files instead of a .png or .dem file to create my own heightmap I either get no response from Gazebo or a crash with the following error:

gzclient: /usr/include/boost/smart_ptr/shared_ptr.hpp:734: typename boost::detail::sp_member_access<T>::type boost::shared_ptr<T>::operator->() const [with T = gazebo::msgs::Response; typename boost::detail::sp_member_access<T>::type = gazebo::msgs::Response*]: Assertion 'px != 0' failed.