- From: Peter Parslow <Peter.Parslow@os.uk>
- Date: Thu, 16 Mar 2017 16:48:04 +0000
- To: "public-sdw-comments@w3.org" <public-sdw-comments@w3.org>
Hi all, This is becoming a really useful resource - as an introduction to the subject area, as well as a set of best practices. Sorry to have not been more involved. I've been reading it again (along with other related articles), prior to attending next week's meeting, and a few things come to mind which could become improvements. 1. URI for Eddystone Lighthouse. It is of course fine to use a URI from Deutsche Nationalbibliothek, and a URL from Wikidata, if only to demonstrate that many URIs can identify the same spatial thing. But I think it would be good to honour the actual owners/operators of the lighthouse by using their reference: https://www.trinityhouse.co.uk/lighthouses-and-lightvessels/eddystone-lighthouse 2. in section 8 about CRS, it says that lat & long "can express a location to within a few metres". In fact there's nothing to stop a lat/long being as precise as you like, and I often find ones which are more precise than their accuracy should support. By which I mean that quite a lot of software defaults to serialising real numbers as decimals with six digits after the decimal place - which is something like 1cm on the ground. That accuracy can only be achieved with professional equipment, but a discussion of accuracy & precision may be out of place in this document (at least, at this section). But perhaps dropping the 'within a few metres' bit would be appropriate.. And in fact, example 3 gives lat/long with seven and 12 decimal places: seven is millimetre accuracy; I'd have to Google the name for a unit small enough for 12 decimal places of a degree - probably smaller than an atom! See http://gis.stackexchange.com/questions/8650/measuring-accuracy-of-latitude-and-longitude/8674#8674 Can I recommend reducing the number of digits in the examples. 3. Further on in section 8, I'm not sure that EPSG:4277 is "the UK National Grid"; my reading of the EPSG register is that this is the code for OSGB36, which is the geodetic reference system on which the project British National Grid is based. The code for the British National Grid is 27700. We don't call it "UK" national grid, because Ireland generally uses a different one. That's all for today; I may get time to read a bit more tomorrow. Peter Peter Parslow Principal Geographic Information Architect Products & Innovation, Ordnance Survey Adanac Drive, SOUTHAMPTON, United Kingdom, SO16 0AS Linked data / map: http://data.os.uk/id/postcodeunit/SO160AS Phone: +44 23 8005 5341 | Mobile: +44 7796 610020 www.os.uk | Peter.Parslow@os.uk Please consider your environmental responsibility before printing this email. This email is only intended for the person to whom it is addressed and may contain confidential information. If you have received this email in error, please notify the sender and delete this email which must not be copied, distributed or disclosed to any other person. Unless stated otherwise, the contents of this email are personal to the writer and do not represent the official view of Ordnance Survey. Nor can any contract be formed on Ordnance Survey's behalf via email. We reserve the right to monitor emails and attachments without prior notice. Thank you for your cooperation. Ordnance Survey Limited (Company Registration number 09121572) Registered Office: Explorer House Adanac Drive Southampton SO16 0AS Tel: 03456 050505 http://www.os.uk
Received on Thursday, 16 March 2017 16:53:57 UTC