I can't say I am familiar with his camping set up. The Northern part of Australia has pretty mild to warm temps (even in winter), so it makes sense to me that he would use a tarp (much cooler with better airflow than a tent).
Again it makes sense to me that he is protecting himself from Mozies with some form of netting. For it to be effective, he would need to ensure that the netting was secured at ground level (otherwise the little blood suckers will find their way in). As PJ has already pointed out, the netting would need to be large enough to ensure space between himself & the netting, otherwise the mini Draculas will be able to reach you through the netting

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So in effect, whilst using a tarp, he is for all practical purposes sleeping inside the inner of a tent
BTW, funnell web spiders are not found in the Nth of Australia.