On Fri, Jan 1, 2010 at 6:49 PM, John Smith <span dir="ltr"><<a href="mailto:deltafoxtrot256@gmail.com">deltafoxtrot256@gmail.com</a>></span> wrote:<br><div class="gmail_quote"><blockquote class="gmail_quote" style="border-left: 1px solid rgb(204, 204, 204); margin: 0pt 0pt 0pt 0.8ex; padding-left: 1ex;">
2010/1/2 Aun Johnsen <<a href="mailto:lists@gimnechiske.org">lists@gimnechiske.org</a>>:<br>
<div class="im">> Even if you have access to good arial photography, remember that it might be<br>
> out of alignment, it can be a good advise to gather some good fixes to check<br>
> the alignment of your photos, this can be several GPS tracks along your<br>
> trail.<br>
<br>
</div>I'm pretty sure the imagery he's refering to is <a href="http://nearmap.com" target="_blank">nearmap.com</a>, which I'm<br>
not sure how they manage it exactly but they seem to be about<br>
sub-metre accuracy...<br></blockquote><div><br>Where are you getting that "sub-metre accuracy" claim from? This thread (<a href="http://www.mail-archive.com/talk-au@openstreetmap.org/msg03414.html">http://www.mail-archive.com/talk-au@openstreetmap.org/msg03414.html</a>), which you contributed to, throws out "3-5 meters", "1-4 meters", and "5 meters or so".<br>
<br>This seems like somewhere that the wisdom of crowds actually applies. I think I'd trust the average of a bunch of independent GPS traces to a single orthorectified aerial - especially in an area which isn't extremely flat. But I guess I might be convinced otherwise, if I'm actually shown the "sub-metre accuracy" claim, which presumably outlines the methods utilized to ensure such accuracy.<br>
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