[Talk-us] dubious church node

ethnicfoodisgreat ethnicfoodisgreat at gmail.com
Sun Oct 1 10:56:47 UTC 2017

Usually when I find a POI for a church that no longer exists, the USGS topo maps also show a church at that location.  Comparing the aerials and the maps confirms the church POI should be deleted (or marked as historic).

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-------- Original message --------From: Carl Anderson <carl.anderson at vadose.org> Date: 9/30/17  11:21 AM  (GMT-05:00) To: Brian May <bmay at mapwise.com> Cc: Kevin Kenny <kevin.b.kenny+osm at gmail.com>, Mark Bradley <ethnicfoodisgreat at gmail.com>, talk-us at openstreetmap.org Subject: Re: [Talk-us] dubious church node 
​A little history on GNIS data, and the Board of Geographic Names.

The US Board of Geographic Names manages names for places and features shown on US govt maps.  They have been using a database to manage the names across maps and map scales. That database is the GNIS.

The ​original GNIS data was populated from all text labels shown on USGS maps.  The most common source was 1:24,000 scale topo quarter quads.  Text from 1:100,000, 1:250,000 and 1:1,000,000 scale maps and larger were included.

The stated map accuracy of these scales  ( https://nationalmap.gov/standards/nmas.html ) is approximately

1:24:000        40 feet1:250,000     416 feet
1:500,000     833 feet
1:1,000,000   1666 feet

The GNIS dataset includes the most precise location for text, when the text appears on maps of different scales.

An example of the kinds of text on the maps is attached.

On Sat, Sep 30, 2017 at 10:46 AM, Brian May <bmay at mapwise.com> wrote:

    On 9/29/2017 11:06 PM, Kevin Kenny

          On Fri, Sep 29, 2017 at 9:33 PM, Mark
            Bradley <ethnicfoodisgreat at gmail.com>


              In the course of my mapping in the American Midwest, I
              have come across several small country churches of GNIS
              origin that no longer exist.  Often there will be a nearby
              cemetery, but the church facility is gone.  I simply
              delete the node.  In one case I know of, the church
              building was converted into a home, so I remapped it


            Of course, if the cemetery is there on the ground, then
              it should be mapped. But deleting the node for a
              demolished church is entirely appropriate. For a church
              converted to a private home, consider:

            building=detached historic:amenity=place_of_worship
              historic:name=* etc.

            if the building still resembles a church. 


    For any arm-chair mappers out there, you cannot assume the location
    of the original GNIS point is accurate at all, unless you have up to
    date evidence it is. So if you see a church point sitting on what
    looks like a house in a residential neighborhood on the aerial, then
    either delete it,  mark it as a FIXME or leave it alone. The person
    working for the Feds who originally mapped the point may have been
    miles off.


    A few thoughts:


    Churches from GNIS seem to be one of the biggest "map noise"
    features for areas I look at. Sometimes the locational accuracy is
    spot on, church is still there and everything is great. Sometimes
    the church is a mile and half down the road on a different block.
    Sometimes its in the middle of the highway. Sometimes in the water,
    etc. When I am quickly reviewing an area and I see a church point in
    the water or on a road, I usually just move it to a halfway
    plausible location without doing more research. It would be nice to
    have a fairly solid process for reviewing these with external data
    that is of known high quality.


    I did a little playing around with the new USGS Map VIewer [1] and
    it has a Structures layer.  This appears to be part of the volunteer
    corps thing w/ USGS, which was (is?) a national program to provide
    higher accuracy points focused on buildings and structures.  I found
    this [2] from 2012 that provides an overview. Looks like they
    intended to contribute back to OSM - but no word on that in the doc.
    Found this site as well [3], but out of time to dig into it for now.
    Anyone know more about this Structures layer? 


    In the USGS Map Viewer, you can click on a structure and see details
    about it. Some say source=centroid - to me this means parcel
    centroid. Many have addresses as well. The map viewer allows you to
    switch the base map to OSM. So then you get a nice QA tool to check
    OSM features in an area. The structures layer doesn't include
    churches, but cemeteries are included. Other features include Post
    Offices, State Capitol Buildings, Hospitals / Medical Centers,
    Police Stations, Prisons, Colleges, Technical Schools, Schools,
    Campgrounds, Trailheads and Visitor Information Centers.


    I have a statewide parcels layer that just shows church polygons and
    labels that I use sometimes use as well for checking churches -
    others are welcome to use it if interested.


    [1] https://viewer.nationalmap.gov/advanced-viewer/

    [2] https://pubs.usgs.gov/of/2012/1209/pdf/ofr2012-1209.pdf

    [3] https://nationalmap.gov/TheNationalMapCorps/#





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