On 1 September 2012 11:35, Russell Edwards <russell...@gmail.com> wrote:
> > I am still curious to know what the positional accuracy of survey markers > is meant to be, if anyone can enlighten. > > First question you have to ask is how old the survey is? Australia as a whole moves north about 7-8 cm a year (from memory), so a 12-13 year old survey has moved about a metre from the start spot. It's a moving target. Survey markers stay pretty accurate in relation to everything around them, but not necessarily in relation to some outside measuring source like GPS. But an even bigger error can be caused by using different projections. I forget which one OSM uses, but using different projections can move a given point 20m quite easily, and a survey marker may well be on a different one. Stephen
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