Gregrs has provided converted data for trig points, with the data obtained from a FOI request. They created a page to explain the process, and made available the converted data as a gpx file https://wiki.openstreetmap.org/wiki/Ordnance_Survey_triangulation_stations .
Jass On Sun, 23 Aug 2020 at 15:13, Nick <[email protected]> wrote: > My thinking was that most people surveying would not use accurate and > precise systems such as differential GPS and/or RTK. So if these systems > were used to accurately and precisely locate distinct local markers (i.e. > trig points, benchmarks etc.) then local surveys could potentially use > these to refine/check their own surveys. This approach would still be based > on community input but could be used as an approach to education (e.g. > local schools involved) as to how surveying works in practice. > On 23/08/2020 12:27, SK53 wrote: > > This approach has been advocated in other European countries, and the > Spanish community imported all the points of the national geodesic network > (e.g., for Extremadura > <https://www.openstreetmap.org/changeset/6041229#map=7/39.254/-6.124>). > They more or less violate the idea of OSM as something which is community > contributed (IIRC each point has "DO NOT MOVE") and often interfere with > objects which do need mapping (churches are a particular point). It's not > clear that this import has assisted improved accuracy of mapping in Spain. > > Many trig pillars are now way out of alignment and mainly of interest as > an artefact. Even benchmarks might not have much relevance as OS surveying > mainly uses differential GPS with reference to their own base network (OS > Net > <https://www.ordnancesurvey.co.uk/business-government/tools-support/os-net/positioning>). > (From the OS website "Ordnance Survey (OS) benchmarks and their heights > haven't been regularly maintained for over 40 years."). > > OS Net is effectively proprietary, there are a limited number of open base > stations for differential GPS in the UK. I do believe differential GPS > (RTK) has a role to play in OSM surveying, although for specific purposes > rather than generic improvement of feature alignment. > > Regards, > > Jerry > > On Sun, 23 Aug 2020 at 10:05, Nick <[email protected]> wrote: > >> I have been looking at what is recorded under this tag in my area. I see >> that there aren't that many and those that are on OSM refer to trig >> points (see also http://trigpointing.uk/). My thinking is that if these >> are accurate and precisely marked on OSM then perhaps they could be used >> for resolving issue such as aerial imagery offsets. >> >> I therefore wondered if it was worth using other data under this tag - >> specifically benchmarks (https://www.ordnancesurvey.co.uk/benchmarks/) >> as there are huge numbers in the UK. If these were marked on OSM and >> their accuracy and precision verified (OS open data is to the nearest >> 10m square and transforming that adds errors), they could be helpful in >> local surveys where they are less than accurate but also for ensuring >> that moving all nodes in an area is valid (not just to match aerial >> imagery). A possible linked organisation with data is >> https://www.bench-marks.org.uk/ >> >> Incidentally, the benchmarks can be helpful if you need to align >> historical maps which have benchmarks shown. >> >> Any thoughts? >> >> >> _______________________________________________ >> Talk-GB mailing list >> [email protected] >> https://lists.openstreetmap.org/listinfo/talk-gb >> > _______________________________________________ > Talk-GB mailing list > [email protected] > https://lists.openstreetmap.org/listinfo/talk-gb >
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