[Talk-us] dubious church node
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:
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
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  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  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 , 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.
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