[Tagging] Feature Proposal - RFC - Survey Markers

[Michael Patrick]

 > My rationale for suggesting this, is that OSM shouldn’t be used to map
historical, non-existent things according to:... I was just proposing that
if neither the survey point nor the structure exists anymore, then it
should be removed from OSM. This would only happen if a natural disaster or
man_made earthworks removed all traces of it...

If one is going to invoke the term 'Survey', the conventions attached to
that word become important. And those have been in existence for thousands
of years and codified into society and manifest themselves on the landscape
in ways even visible from space.

Any survey point is not a singular 'thing'. It is only part of a large
network system of things, and it's definition both abstract and as some
sort of physical object like a monument are defined by it's relationships
to the other points ( and their objects ). If those other objects exist,
and are observable in some manner, the individual survey point still exists
- 'witnessing'.

Because there is a couple thousand years of history there are well
established lexicons and terminology regarding both the abstract and
practical objects as they are in the real world, including the state (
status ) of any sort of marker. And there are easily available data schemas
and registries of that information, at the global, national,
state/province, county, and city levels - and some domain specific like
public utilities and transportation:
https://earth-info.nga.mil/index.php?dir=surveys&action=surveys ,
https://geodesy.noaa.gov/datasheets/ ,
https://www.wsdot.wa.gov/monument/info.aspx ,
https://maps.rentonwa.gov/Html5viewer/Index.html?viewer=SurveyControl ,
https://seattlecitygis.maps.arcgis.com/apps/webappviewer/index.html?id=32c7608f6ed145feaf27f18bb12ef200
( note that 'destroyed' monuments are still tracked ).

The British Ordnance Survey would provide many more examples, since they
mapped most of the world and established the basis of many country's
current systems.
Most of the US PLSS monuments are not visible to the casual observer,
because roads were built on the main section boundaries, along with many
other reasons markers may have been deliberately concealed (
https://www.berntsen.com/Surveying/Specialty-Markers/DEEP1-Magnets-for-Surveys
or a small levels, a buried length of rebar ). So not necessarily, without
consulting records, possible to determine the status or current 'existence'
of a marker, i.e. if it is 'historical' ( obsolete ).
There are 'historical' designated monuments that are visible ( The most
notable of these is the Prime Meridian itself:
https://theconversation.com/heres-why-the-greenwich-prime-meridian-is-actually-in-the-wrong-place-46302
and  'Four Corners'
https://www.outtherecolorado.com/adventures/did-you-actually-visit-the-four-corners-when-you-visited-four-corners-national-monument/article_71952e84-0933-551d-a74a-250759a5ecaf.html
... " it is 1,807 feet east of where it should be, according to a U.S.
National Geodetic Survey spokesperson" )

In terms of OSM utility, many times I've used benchmarks which are
'invisible' to the ordinary ground observer to assess the quality of OSM
road alignments, boundaries and other features and to determine the
qualities ( orthorectification ) of aerial and satellite imagery (
especially in mountainous terrain - especially important with GIS imports
of public data of questionable lineage.

'Destroyed' is perfectly valid as a status - but it doesn't mean
'non-existent', it is a temporary condition in the network, until
'recovered'. The presence of a marker / monument doesn't make it a 'survey
point'. Many markers aren't 'visible', sometimes by design or circumstance,
but verifiable with proper equipment and inferring their existence from an
official database isn't any different than masses of other imported data in
OSM - notably address points. 'Historical' markers ( but obsolete for
survey' are visible, and even misplaced ), but actual invisible or
temporarily 'not present' survey markers appear OSM-ishly 'historical' ).

Michael Patrick



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