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<div class="moz-cite-prefix">On 30/01/2015 14:12, St Niklaas wrote:<br>
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<blockquote cite="mid:DUB123-W328ECBE7EBA4C481A3A6AB9A310@phx.gbl"
type="cite">
<div dir="ltr">> From: François Lacombe
<a class="moz-txt-link-rfc2396E" href="mailto:fl.infosreseaux@gmail.com"><fl.infosreseaux@gmail.com></a><br>
> <br>
> Since OSM editing tools aren't AutoCAD you can't be 100%
precise on the<br>
> geometry.<br>
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</blockquote>
<br>
Exactly so.<br>
<br>
<blockquote cite="mid:DUB123-W328ECBE7EBA4C481A3A6AB9A310@phx.gbl"
type="cite">
<div dir="ltr"><br>
<p class="MsoNormal" style="margin: 0cm 0cm 10pt;"><span
style="font-family:
"Calibri","sans-serif";
mso-ansi-language: EN-US;" lang="EN-US">Francois if you’re
using JOSM you’re be able to work
up till 0,06 - 0,04 =0,02 m accuracy </span></p>
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</blockquote>
<br>
No. Unless you can measure accuracy on the ground to that level of
precision, you simply can't*. The imagery sources availble to OSM
aren't that accurate, and even the aggregated traces of many, many
consumer GPS units won't hit that accuracy. 0.06m is a tiny amount
compared to the amount that natural processes can cause a particular
"location" to move**.<br>
<br>
A good rule of thumb for OSM is "don't try and map more accurately
than your sources". If you only have aerial imagery, or only have a
few GPS traces, don't try and map every last hedgerow, since you
simply don't know how accurate the sources that you're working from
are. Instead, go out and collect more data. For example, once you
know how aerial imagery compares to lots of GPS traces (and
vice-versa - GPS traces can have a systematic offset due to terrain
and even "what side of a road people are allowed to walk down")
you're in a much better position to contribute.<br>
<br>
Cheers,<br>
<br>
Andy<br>
<br>
PS: Please don't reply to digest posts largely unedited. The very
first line in your reply mail was, quoted, "When replying, please
edit your Subject line so it is more specific". Even if you do edit
a digest post down it'll still destroy the threading of the mailing
list. Many, many people rely on this to make the process of reading
lists such as "tagging" less of a chore (it's much easier to "mark a
thread as read" than it is to go through every post about
semicolons, patron saints or pipelines one by one). If you don't
have a mail reader than can handle non-digest mail, you probably
need to change the way that you read mail.<br>
<br>
* The exception is where you're triangulating from points measured
with an accuracy beyond what consumer kit can provide. I'm looking
forward to seeing "triangulation via theodolite from X" in an OSM
source tag :)<br>
<br>
** <a class="moz-txt-link-freetext" href="http://www.bbc.co.uk/news/science-environment-12732335">http://www.bbc.co.uk/news/science-environment-12732335</a><br>
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