[Talk-GB] Accuracy of cadastral parcel alignment

[Michal Vinarek]

Hey Tom,
looks like an interesting claim with the perfect alignment, although I 
am myself a bit skeptical.
For example, importing raw cadastral shapefile for Glasgow (from 
https://ros.locationcentre.co.uk/inspire/) and comparing it to the 
cadastral overlay shows some misalignment. Not sure if it's just my JOSM 
mucking up the import/overlay though.

(hopefully the image works - blue lines are the overlay from JOSM; you 
can see there is some misalignment in between these two sources)
Btw, the source is mentioned in OSMUK presentation here: 
https://osmuk.org/wp-content/uploads/2020/07/UK_open_data-20200704.pdf 
(you could try your local area to see if you have similar misalignment 
issues?)

Maybe there is someone from OSMUK on this mailing list that could 
perhaps explain whether the overlay is good to be used as a sort-of 
point of truth for other imagery alignment? It would be awesome to have 
a single point of truth in that regards for UK; for example mappers in 
Czech Republic can use a fairly detailed cadastral map (CUZK RUIAN) to 
align imagery for quite some time now.

Regards,
Michal


On 03/03/2021 13:04, Tom Crocker wrote:
> I spotted the new land registry imagery in JOSM - thank to those who 
> have made this available - and the claim of perfect alignment in the 
> info box. I assume this means perfectly aligned with Land Registry's 
> data and therefore some default legal position on ownership (although 
> my memory from buying a house was that boundaries aren't just about 
> what is marked on a map). Anyway, looking at the layer it seemed 
> closer than the Bing alignment to what I have been mapping to based on 
> quite a lot of GPS tracks, but still offset by about 1 (metre?) in 
> either direction. Although there are going to be boundaries that have 
> shifted and presumably inaccuracies in the surveying, would it be fair 
> to assume that the majority of their data is likely more accurately 
> placed than I can estimate with multiple tracks from my phone GPS, 
> particularly around new estates where I guess OS have done a recent 
> survey with far better equipment than me?
>
> In short, should I just switch to using their typical alignment as 
> it's probably better?
>
> Thanks
>
> Tom
>
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