$ sudo apt-get remove gnat-gps 

Uninstall gnat-gps including dependent package

If you would like to remove gnat-gps and it's dependent packages which are no longer needed from Ubuntu,

$ sudo apt-get remove --auto-remove gnat-gps 

Use Purging gnat-gps

If you use with purge options to gnat-gps package all the configuration and dependent packages will be removed.

$ sudo apt-get purge gnat-gps 

If you use purge options along with auto remove, will be removed everything regarding the package, It's really useful when you want to reinstall again.

$ sudo apt-get purge --auto-remove gnat-gps 

See Also,