<html>
<head>
<meta http-equiv="Content-Type" content="text/html; charset=utf-8">
</head>
<body text="#000000" bgcolor="#FFFFFF">
<div class="moz-cite-prefix">On 21-Nov-17 12:07 PM, Andrew Harvey
wrote:<br>
</div>
<blockquote type="cite"
cite="mid:CAD5Vjsv0kpR7MrXD+0LzzSDMWrrFmhkp1KPSukT1A1FEb029fg@mail.gmail.com">
<div dir="ltr">
<div>Being able to distinguish different types of survey marks
and points is very much needed in OSM, it would be great to
see this formalised on the wiki.</div>
<div><br>
</div>
<div>I like the idea of modelling it after <a
href="https://wiki.openstreetmap.org/wiki/Seamarks/Categories_of_Objects#Control_Points_.28CATCTR.29"
target="_blank" moz-do-not-send="true">https://wiki.<wbr>openstreetmap.org/wiki/<wbr>Seamarks/Categories_of_<wbr>Objects#Control_Points_.<wbr>28CATCTR.29</a>
as that seems well thought out.</div>
<div><br>
</div>
<div>I like the idea of using configuration as a sub key to
survey_point, rather than the undocumented by suggested tags
of "triangulation_point=yes and benchmark=yes".</div>
<div><br>
</div>
<div>My only question is the wiki page currently says "Since
multiple survey points are possible on one object (eg. a
benchmark on a triangulation point/pillar) then in order to
avoid multiple values within one key, such as a
semicolon-delimited list in survey_point=*, it may be
advisable to use something like triangulation_point=yes and
benchmark=yes to allow clean coexistence of tags on one
node.".</div>
</div>
</blockquote>
<br>
I think that triangulation points are not normally used this way?
Where required the placement of the equipment on the exact centre of
the point may mean that the structure needs to be disassembled. <br>
I'd think any triangulation point could be used this way as a bench
mark and they may all be equipped for it? <br>
Might have this from one of Len <span class="st">Beadell</span>s'
books? Or from talks with a past neighbour - a professional
surveyor. <br>
<br>
<blockquote type="cite"
cite="mid:CAD5Vjsv0kpR7MrXD+0LzzSDMWrrFmhkp1KPSukT1A1FEb029fg@mail.gmail.com">
<div dir="ltr">
<div><br>
</div>
<div>How would your proposal work with multiple survey points on
the one object? I've never come across this so not sure
myself.</div>
</div>
</blockquote>
<br>
Any professional knowledge on this would be welcome. <br>
<br>
<blockquote type="cite"
cite="mid:CAD5Vjsv0kpR7MrXD+0LzzSDMWrrFmhkp1KPSukT1A1FEb029fg@mail.gmail.com">
<div dir="ltr">
<div><br>
</div>
<div>I think observation is a valid configuration, as I've seen
observatories used as the datum on old maps.</div>
</div>
</blockquote>
<br>
Any place can be used as an 'observation point' .. so I don't see
any reason to map something that has no ground presence? <br>
Or is there some artefact left behind? And then would not that be a
form of benchmark? <br>
<br>
<blockquote type="cite"
cite="mid:CAD5Vjsv0kpR7MrXD+0LzzSDMWrrFmhkp1KPSukT1A1FEb029fg@mail.gmail.com">
<div dir="ltr">
<div class="gmail_extra"><br>
<div class="gmail_quote">On 21 November 2017 at 10:47, Warin <span
dir="ltr"><<a href="mailto:61sundowner@gmail.com"
target="_blank" moz-do-not-send="true">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">Hi,<br>
<br>
There have been attempts in the past to add sub tags to
man_made=survey_point <a
href="https://wiki.openstreetmap.org/wiki/Tag:man_made%3Dsurvey_point"
rel="noreferrer" target="_blank" moz-do-not-send="true">https://wiki.openstreetmap.org<wbr>/wiki/Tag:man_made%3Dsurvey_po<wbr>int</a><br>
<br>
To me there are 2 'types'. they are quite different;<br>
<br>
Triangulation (or 'trig point') that are visible over
quite some distance (say over 2 km),<br>
used to triangulate a position without having to go to the
mark. Usually a pole standing on top of a rise/hill.<br>
<br>
Benchmarks that are visible on the surface but cannot be
sighted at any distance. They can be small brass plaques
fastened to the ground or engraved into stone.<br>
These are used by surveyors by placing a tripod over the
mark, thus have to be locally approached.<br>
<br>
If consideration is given to <a
href="https://wiki.openstreetmap.org/wiki/Seamarks/Categories_of_Objects#Control_Points_.28CATCTR.29"
rel="noreferrer" target="_blank" moz-do-not-send="true">https://wiki.openstreetmap.org<wbr>/wiki/Seamarks/Categories_of_O<wbr>bjects#Control_Points_.28CATCT<wbr>R.29</a><br>
<br>
then expanding survey_point in a similar manner could be<br>
<br>
survey_point:configuration=tri<wbr>angulation/benchmark<br>
<br>
I use 'configuration' rather then 'type' or 'category' as
it is more specific as to what is meant.<br>
<br>
Any thoughts?<br>
Are there any other configurations?<br>
<br>
<br>
</blockquote>
</div>
</div>
</div>
</blockquote>
<p><br>
</p>
</body>
</html>