On Tue, Aug 7, 2018 at 6:41 PM, Graeme Fitzpatrick <graemefi...@gmail.com> wrote:
> > > > On 7 August 2018 at 21:56, Daniel Koć <daniel@koć.pl> wrote: > >> >> For example nobody would say that a city is a point > > > I'm not disagreeing with you, but people do refer to them, & somehow even > measure them, as points! > > I'm sure that you have the same situation in your country but an e.g. is > my State capital, Brisbane: https://en.wikipedia.org/wiki/Brisbane, which > > covers an area of 15842 km2, but is still apparently found exactly at: > ... > > Quite so. To measure distances between towns/cities, some point is needed. While in theory someone wishing to do so could query for the Admin level outline and compute the centroid, when a government entity has declared a named point to match the Admin level boundary, it's convenient if everyone uses the same one. The old Boston Milestones measured distance from the entrance to town at Boston Neck; but modern distances usually measure to the center of the Statehouse Dome. The US Geodetic Survey includes City, Town, and settlements among their point data for annotating maps -- this is where the label goes when a USGS GIS system makes a draft map, until a cartographer moves it for aesthetics. (I rather suspect the town names on OSM.org renderings come the same way and not from Admin level boundary ways.) I don't know if those were imported with Tiger or imported separately, but i think they're in OSM already. Should we delete the USGS named town points because they don't match a verifiable marker on the ground at that location? No. Let's not take ourselves so seriously that we reject open-licensed data freely given. The mapping ground truth dictum was a reaction to the UKOS's refusing to open-license their taxpayer owned data; some have made a virtue of a necessity of ground-truth field-mapping, GPS-on-bicycle, but let us rejoice that some governments have learned the folly of the closed shop. It's not that we Yanks are lazy arm-chair mappers, it's our US Gov did something right for a change. (We did have a decade when the new weather radar data was only available via private contracts, which helped offset the radar hardware and software upgrades, but with the rapid growth of the WWW they sensibly chose not to renew that contract; and likewise the National Library of Medicine collection of Abstracts -- which i was trying to profiteer on when VP Gore freed it. I'm glad; our marketing dept was made of fail anyway.) If there are countries which for which open-licensed town centers aren't available, the local mapping communities can decide what is right for them. Postoffice, Town Hall, Centroid, Flagpole, whatever. -- Bill Ricker bill.n1...@gmail.com https://www.linkedin.com/in/n1vux
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