The meaning of the dots is not entirely known, and there are various theories. What seems to be true is that this style of ‘dot painting’ appeared in the 1960’s in the Central and Western Desert areas, principally amongst the Papunya and Yuendumu communities. The dots are thought primarily to have been used to obscure sacred details that the ‘uninitiated’ were not allowed to view. So they are a type of masking.
And yes, the various shapes do have specific meaning. In this art example you can see water holes and rivers, but specific meaning is often dependent on the region and group who created the art.
Ps. I have a goose-neck (hook) boomerang made for me in the early 70’s by a Yuendumu elder using traditional techniques and covered in red ochre (wilgi). A prized childhood possession that I will post some photos of at some point.
I'm not familiar with Aborinal art and would be interested in comparing the two types.
Thanks for sharing,