Re: [Talk-GB] Finally a RTK / NTRIP Broadcaster in London

[Adrian via Talk-GB]

@ Grant Slater
Thank you for spotting this and making it known.

One thing you need to know when using an RTK base station, is what is the 
reference (datum). Unfortunately there is no convention for how this 
information is given, and it is often not given at all. The stations listed by 
Grant are on the Eurasian tectonic plate so the reference will be either ETRS 
or ITRS ("WGS 84"). WGS 84 is the datum used in OSM.

I have previously connected to several of the stations on the list: DARE, HERS, 
HERT and SHOE. All of these are on ETRS although HERS has a small position 
error. I tried connecting to LICC and it is on ITRS. (I estimate there is a 
position error, relative to ITRS, around 12cm too far north, 8cm too far west 
and 31cm too high.) I think a mistake has been made in configuring the LICC 
station. Incidentally, LICC is at Imperial College in South Kensington. There 
is a site information page at 
http://epncb.oma.be/_networkdata/siteinfo4onestation.php?station=LICC00GBR If 
you click on Data Provided you can see any warnings that have been logged. It 
was the warning here about a position error that prompted me to check it out. 
The website I just referred to evidently expects the reference to be ETRS.

The stations on Grant's list are of a type known as Continuously Operating 
Reference Stations (CORS). Stations of that type would be expected to produce 
results consistent to the millimetre. The ITRS position of LICC shifts by a 
millimetre every two weeks, so I hope they have an automated system, or at 
least a simple system, for updating the position it is broadcasting.

If you have a consumer SatNav you probably can't tell the difference between 
ETRS and ITRS. But if you are using RTK you certainly can tell the difference. 
In south-east England, at the time of writing, ITRS gives a position 52.0cm 
further north and 53.5cm further east than ETRS. This gives a horizontal 
distance of 74.6cm. The horizontal distance increases by 2.4cm per year. The 
altitude difference is less than 0.2cm.

If you record a tracklog using RTK from seven of the eight stations in the 
list, the tracklog will be in ETRS. You will need to convert it to ITRS for use 
in OSM. If the tracklog covers a small area, you can just apply a fixed offset 
to the latitudes and longitudes. Unfortunately I don't know of any tool which 
makes this simple to do.

Someone in France has organised funding for an independent network of open RTK 
base stations. (The availability of free RTK base stations was even worse in 
France than in the UK.) See https://centipede.fr/ They have produced detailed 
instructions for setting up a base station, including a shopping list, how to 
assemble the equipment, preconfigured software, and how to obtain the position 
of the base station to within a couple of centimetres. It also covers setting 
up a receiver for RTK. They have set up a server to broadcast all the streams 
and there are already several dozen stations in operation. They will soon be 
prevented from setting up a VRS, only by the cost of the software for doing 
that. The documentation is all at https://jancelin.github.io/docs-centipedeRTK/ 
It is in French, but for those who don't speak French, I expect a well-known 
online service would produce an adequate translation. There is a subscription 
RTK stream service covering many countries, which professionals use. They no 
longer quote prices on their web site, but when they did, the entry-level 
subscription for real-time access was around £4000 per year. IIRC, that gave 
the subscriber access to a maximum of five simultaneous VRS streams and 
included access to a two-way satellite link, for areas where there was no 
mobile phone signal.

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Re: [Talk-GB] Solar update Q3 2020

[Dan S]

Hi all,

Thanks Jerry for this very good analysis. 250,000 is a fantastic
milestone - thanks to everyone.

I don't have very much to add to Jerry's report. The change in the
imagery has made a massive difference to aerial mapping - I can
certainly say that for my patch of London, where I'm quite pleased to
discover we exceeded 100% :) In my experience the imagery made it much
more feasible to draw solar panels as polygons (ways) rather than
nodes, so I'm generally doing that. (I'm not able to do as high
quantities as others can.)

Orientation - very interesting, I guess I'll start using the
"direction" tag too instead of the one we were previously using.
Mapping the orientation (the compass direction) of solar panels is
very useful for data consumers - it really helps in predicting the
power they'll be generating. So yes, I'd really encourage people to
put the direction=* tag on there.

Cheers
Dan

Op do 1 okt. 2020 om 14:18 schreef SK53 :
>
> I'd meant to provide an update at the end of August, just after the peak of a 
> frenzy of adding solar power from the new higher quality Bing imagery. As I 
> didn't, now is a good time to summarise recent progress: September has seen 
> more modest gains.
>
> Some headline figures:
>
> We passed 250k OSM elements on 31st August and 30% completion (measured 
> against FIT, which does not cover the totality of solar installations) a few 
> days later
> 2 additional LA areas joined the, anomalous, Isles of Scilly, in passing 100% 
> of the FIT target: Torridge and Tower Hamlets.
> 7 more LAs have reached >90% of FIT. Joining Nottingham and Plymouth, these 
> are Canterbury, North Devon, Exeter, Torbay, Derby and Chesterfield
> 30 LAs are now between 80 & 90% of the FIT numbers
> in total around 100 LAs have over half of the FIT totals mapped, including 4 
> in Greater London
> Devon, Derbyshire & Nottinghamshire have all LAs over 80%
> Leicestershire, Lincolnshire and Warwickshire are around 60% complete
> Much of the rest of the West Midlands is around 30%
> Edinburgh was the first Scottish LA to pass 50% (thanks Donald)
> Visibility of solar in Greater London has changed dramatically. Russ, Dan & 
> Yvonne have been the most active mappers.
>
> From my own mapping, it's now clear that in most parts of the country the 
> imagery is probably good enough to find at least 90% of installations. This 
> raises the bar compared with previous imagery where for most LAs finding much 
> more than 50% of solar was too hard to be practical. It perhaps also changes 
> what our focus should be. The following paragraphs touch on some of these.
>
> The other significant aspect of better imagery is that it is now feasible to 
> provide module counts and orientations for the vast majority of panels. At 
> present only 8.5% of the panels already mapped have these tags (although this 
> represents 20k panels, valuable in its own right). I've therefore moved to 
> improving the percentages in the counties I focussed on recently (Devon, 
> Derbys and Notts). It's slightly tedious work, but I think it's now important 
> to avoid building up 'tagging debt' in this area. For LAs with a lower 
> percentage of mapping (upto 60%) it's often possible to combine adding these 
> tags with looking for unmapped solar power, which is rather more engaging, as 
> can be seen by totals for places like Gedling, Rushcliffe & Derbyshire Dales. 
> This latter type of activity can combine well with general updating of an 
> area, refinement of existing elements and correction of errors. If half the 
> new panels added as we advance to 300k have these tags we'll double this 
> percentage. I've moved to generally using direction rather than 
> generator:orientation because this is visualised in iD and I can't see any 
> ambiguity in the use of direction on solar elements (the exception is where 
> solar tags have been added to a building). This overpass-turbo query can be 
> used to visualise the status of solar within any LA: green has both tags, 
> purple is a large installation with "lots" of modules, red lacks orientation 
> & module count, yellow & orange lack one or other.
>
> Frederik mentioned a while back about solar elements in places where little 
> else is mapped. Solar is slightly unusual for OSM in that the utility of the 
> data in most cases needs fairly comprehensive coverage, whereas a single 
> address is useful if I want to route to it. Use of nodes for much of the 
> mapping does allow local mappers adding more detail to correct position and 
> so on, and there is a small, but steady, flow of edits of this type.
>
> Adding buildings themselves comes up against the imagery alignment issues 
> which have been discussed here recently, and therefore, in general, needs 
> more care. In many places there were already substantial numbers of buildings 
> mapped, but a particular problem is that these can appear misaligned with 
> modern imagery (in some places as much as a 5 m discrepancy). In