Here is a list of all namespaces with brief descriptions:

NEigen
Nfreeglut_minimal
Ng2o
Nbal
Nceres
Ninternal
Ncholmod
Ncsparse
Ncsparse_extension
Ng2o
Nlogging
Ninternal
Ng2o
Ninternal
Nlogging
Nopengl
Ntutorial
Ntypes_icp
Ninternal
NSlamParser
Nstd