<div dir="ltr">Hi Warin and all, <div><br></div><div>I am not sure what you dislike in "accuracy". Accuracy is how far the measured mean value is from the actual value (<a href="http://en.wikipedia.org/wiki/Accuracy_and_precision" target="_blank">http://en.wikipedia.org/wiki/Accuracy_and_precision</a>). However we can start calling it a "trueness", to follow the ISO definition. If you mean something else, please explain, and I believe it would deserve a page in OSM wiki.</div><div><br></div><div>Now, I am talking about the absolute trueness. That is, how far a POI is according to the map from its actual position on the planet. No, I don't forget that the planet surface is moving relative to the GPS coordinates. Even more so, there are local surface movements, especially if the survey marker is located, say, on a bridge or close to an excavation site. It should be considered when defining this "non-movable" POIs.</div><div><br></div><div>Taking into account the inherent precision of the survey marker position (they are designed to have a well-defined position), it does make sense to have OSM data for them defined better than for all usual elements.</div><div><br></div><div>At the same time, if you are talking about common use, these POIs are of little interest to "normal" users. So their specific properties will not disturb anyone.</div><div>However, some mappers may be in possession of the surveying tools allowing them to have better trueness than possible with a GPS, provided that they have some good reference points. Survey markers are designed just for that. For these mappers, the absolute location of the survey markers is important, and I see no reason to prevent them from having it in OSM. </div><div><br></div><div>> OSM renders distort road widths according to their classification .. that is normal mapping for road navigation. If you wanted air navigation then the actual road width would be better to render, with runways having more emphasis. </div><div><br></div><div>True. However the underlying data is independent from how a specific renderer represents each element. A street is usually just a line, thus having no width.</div><div><br></div><div>Cheers,</div><div>Kotya </div><div><br></div><div><br></div></div><div class="gmail_extra"><br><div class="gmail_quote">On Tue, Dec 30, 2014 at 12:50 AM, Warin <span dir="ltr"><<a href="mailto:61sundowner@gmail.com" target="_blank">61sundowner@gmail.com</a>></span> wrote:<br><blockquote class="gmail_quote" style="margin:0 0 0 .8ex;border-left:1px #ccc solid;padding-left:1ex">
<div text="#000000" bgcolor="#FFFFFF">
<div>On 30/12/2014 6:41 AM,
<a href="mailto:tagging-request@openstreetmap.org" target="_blank">tagging-request@openstreetmap.org</a> wrote:<br>
</div>
<blockquote type="cite">
<pre>Date: Mon, 29 Dec 2014 15:27:23 +0100
From: Kotya Karapetyan <a href="mailto:kotya.lists@gmail.com" target="_blank"><kotya.lists@gmail.com></a>
To: Rainer Fügenstein <a href="mailto:rfu@oudeis.org" target="_blank"><rfu@oudeis.org></a>, "Tag discussion, strategy and
related tools" <a href="mailto:tagging@openstreetmap.org" target="_blank"><tagging@openstreetmap.org></a>
Subject: Re: [Tagging] Accuracy of survey
Message-ID:
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Since such reference points are quite common, I would support the idea of
creating a special tag for them, requiring that they are not moved. However
we need a clear consensus on how we define the "sufficient" accuracy and
how the data for such points will be updated.</pre>
</blockquote>
<big>Ultimate 'accuracy'? You do realise that the tectonic plates
are moving? So your reference points need to include a date so
they can be corrected for the drift. You'll find that data is
available for those survey reference points .. together with their
precision. Do you want to update these points to maintain their
'accuracy'? How often? </big><br>
<big>Survey reference points are 'quite common' in built up areas
... but not in remote locations. And depending an the age and how
precise the survey was will have some effect on their 'accuracy'.
One surveor in Australia forget to allow for the temperature
effect on this measurement chain .... back when chains were used.
</big><br><span class="">
<blockquote type="cite">
<pre>
I disagree with the point of view that an accuracy sufficient for consumer
GPS devices is sufficient for OSM and therefore there is no problem here.
Nobody ever declared that OSM is for smartphone users. We are trying to map
the world, and accuracy should be of primary interest for this project.
</pre>
</blockquote>
<br>
</span><big>Again the word 'accuracy'. <br>
<br>
Context 1.<br>
I have advised one mapper in their diary that most, if not all,
users will be using their data entry with similar equipment to
what they have .. so any 'inaccuracy' will also be present for the
other users. Thus what they map should represent what is there and
should be usable as a map .. considering that the GPS information
may be very vague under the tree cover present and the local
cliffs etc. <br>
<br>
Context 2<br>
I will be mapping a track that is covered in a few places .. by
an over hanging cliff. As such it is not visible by satellite ..
nor will the GPS track be that 'accurate'. So I'll be mapping it
from the available information that I have then - a few photos, my
track and the satellite image. It will take me about a week to
traverse the area. No shops etc. <br>
<br>
I would rather have the less 'accurate' representation of what is
there compared to a blank area. I've plotted one track that goes
from one place to another (personal knowledge).. where it is not
visible on the satellite view I've plotted it as a straight line..
I know it is not a straight line but it is the best I can do and
conveys the information that the track is connected, and being
straight in that hilly area also conveys that the information is a
guide. I know there is a similar tack a bit north of this track ..
but cannot reliably get the entry and exit points .. so have left
that off as I view it as unreliable for use. I have come across
similar in other areas of the world .. but I found the satellite
image had better information - so '</big><big>improved' the
information. </big><br>
<big><br>
--------------------------<br>
OSM primary interest? <br>
1) to be USEFULL. <br>
meaning to have information desired by the user <br>
sufficient representation and detail to be able to navigate to a
desired place. <br>
<br>
Many usefull maps have distortion - to include more details on
particular objects or to simply emphasise to those objects.<br>
<br>
OSM renders distort road widths according to their classification
.. that is normal mapping for road navigation. If you wanted air
navigation then the actual road width would be better to render,
with runways having more emphasis. </big><br>
</div>
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<br></blockquote></div><br></div>