Art Historical Question -- Albert Namatjira

Can someone help me "term" the art of the Australian painter Albert Namatjira? Four postage stamps of his paintings have been issued.
http://w1.1429.telia.com/~u142900356/frame_AustraliaNamatjira.htm

At first I thought of Naivism, but this is not the correct choice. Neither is Realism, because most artists will claim to paint "what he sees", so any painting could be termed Realism ...

The closest I can come is Indigenous Art, but in some way this sounds "derogative" to me.

I have searched Google (keywords: paintings albert namatjira) and a lot of links pop up, but none of them
"categorize" him. His paintings are charming and well done, so they have come to stay on my site -- I just need to know a bit more about him in an arthistorical context. Any lead would be appreciated

Thanks Rich. I was just browsing Australian art links when your answer rolled in, and you are correct. In fact, both terms, Aboriginal and Indigenous, are used. So I can go on with my site ...

The closest I can come is Indigenous Art, but in some way this sounds "derogative" to me.

Quite correct, and appropriate Mette,
I have some postal material , souvenir sheets etc on this marvelous artist, if you offer a suitable email address
I'll email 350dpi scans for you.