On 13 September 2013 19:59, ael <law_ence....@ntlworld.com> wrote: > No one has mentioned the OS gps (passive) stations: for example > http://www.openstreetmap.org/browse/node/472420260 > http://www.ordnancesurvey.co.uk/business-and-government/help-and-support/navigation-technology/os-net/surveying.html > > Can we not use them at least for some reference points? >
Interesting. Unfortunately it looks as though OS Net slipped past their commercial people as they use the term "freely available" on their web site without giving a precise legal definition of what that means. Given the intended use (all high accuracy surveys in the UK) there seems to be an implication that they aren't claiming a database copyright, but OSM will probably need a clearer legal statement. OSTN02 seems to have the same licensing uncertainty. I would note that even if a relatively restrictive licence were to apply, OS allow checking of accuracy, as long as you don't use the measured error to correct the inaccurate data. Depending on exactly which ground feature represents the station, BIng datum), Bing and the consumer grade GPS survey differ by between 5.2 and 6.2m. Bing and StreetView agree quite well at that point, but diverge towards the West. The BIng error in the typical range, at this point. Are the ETRS89 coordinates given on the monument itself, as they would be individual statements of fact, much like an individual address with postcode? (OS Net allows for movement, so the highest accuracy values will not be fixed.) Without survey quality GNSS receivers, these points are probably mainly of use for calibrating imagery. It's a pity they aren't all clearly visible on the aerial view, my local one, which appears to be within centimetres of Bing, is only identifiable because OS have measured the distance from the local trees. When the rain stops, I'll have a look at what is on the ground, and try for a long average GPS reading. I'll also try and get on the ground measurements from the trees in case the station coordinates are considered fair game, but the sketch map details aren't (looks like a surveyor's tape is on the shopping list - I guess class III, at about 0.05% is good enough, compared with GPS). I note that a lot of them are on private land and require permission from the landowner to gain physical access. PS. The OSTN02 conversion tool, which presumably contains the table, has a BSD Licence, according to <http://www.ordnancesurvey.co.uk/business-and-government/help-and-support/navigation-technology/os-net/grid-inquest.html>. If that is correct, I can see no reason why the os.openstreetmap tiles should not be rectified based on OSTN02. The data also seems to be available in lat/long to lat/long forrmat, also with a BSD licence. _______________________________________________ Talk-GB mailing list Talk-GB@openstreetmap.org https://lists.openstreetmap.org/listinfo/talk-gb