At the time of photographing this spider at Bitter Springs in the Northern Territory of Australia I was told it was a Saint Andrew's Cross Spider Argiope keyserlingi. That would make it a relative of the Wasp Spider A. bruennichi that I get in the orchard here in France.
I'd appreciate it if any reader can confirm its identity. I'm not totally convinced it's not a Golden Silk Orb-weaver Nephila edulis or something similar. The red palps, black abdomen tip and otherwise lack of obvious pattern on the abdomen have me puzzled.