They are a good source of information about landscape history, and are used by local government and developers to help assess the impact of development proposals on the historic landscape.
Maent yn ffynhonnell dda o wybodaeth am hanes y dirwedd ac fe'u defnyddir gan lywodraeth leol a datblygwyr i helpu i asesu effaith cynigion datblygu ar y dirwedd hanesyddol.