[Tagging] [OSM-talk-be] cadastral plan now open data

[Lionel Giard]

André, i don't really see your point with the argument you made about
cadastre data. i don't know of anybody looking to use this data to add
building into OSM. It is outdated data regarding buildings and roads in a
lot of different place in Belgium. And as, the people at cadastre are not
the source for these data, they don't need to update it anymore !  Most
people are only using the default imagery (they often don't know about
anything else).

When tracing buildings, we should always base our self on the PICC for
Wallonia or Urbis for Brussels or GRB for Flanders and the relevant best
imagery in each case (comparing them keeping in mind that vectorial data
are not up to date everywhere at the same time).

To quote a report from the last PICC meeting in June, wallonia have the
following idea on official source :

> Wallonia is planning a “*georeferentiel*” (base of layers that are high
> accuracy and authentic source) within the application of INSPIRE.There are
> 4 major datasets that will be made as accurate as possible and with one
> authentic source for each:
>
>    - *buildings* (in PICC),
>
>
>    - *admin limits* (in cadastre),
>
>
>    - *addresses* (in ICAR) and
>
>
>    - *Roads* (in PICC/”direction des routes” collaboration with
>    attributes (like primary, secondary, highway, bridge,…) on road, not only
>    geometry).
>
> from:
https://wiki.openstreetmap.org/wiki/WikiProject_Belgium/Contacts_with_local_autorities/Wallonia/Compte_rendu_Rencontre_des_utilisateurs_du_PICC_Juin_2018

So cadastre is really about admin. limits and parcels :
- For admin. limits i already talked about it before (as quoted, it is even
the authentic source for all Belgium apparently),
- and for parcels, there is an open debate about adding this information to
OSM (mainly because it is huge amount of work to maintain it) -> as
discussed on the wiki page https://wiki.openstreetmap.org/wiki/Parcel

So there is no ambiguity in what official data exist, the only problem is
that ICAR for the addresses is not yet finished for all municipalities (and
not complete in the PICC as far as i know ?! but i may be wrong about that)
and more importantly, it is not open nor viewable except for special
customers. So we still need to rely on tracing from the imagery and the
PICC WMS at the moment (for buildings, roads and addresses) and now, the
Cadastre data (or wms) to maybe update admin limits.
Note that these official data are considerably improving over time ! They
are still outdated or imprecise in some place, but even then it is still
the official source at the moment (so we should NOT copy blindly as you
said, but compare with recent imagery and survey !!!). The plan is to make
an update cycle closer to 1-2 years (for every municipalities) for the
PICC, but they are still far from it (6.5 years of average update time).

Is there something i'm missing out in your explication ? If so tell me, i
may not understand all your point !


Le ven. 21 sept. 2018 à 23:23, Martin Koppenhoefer <dieterdreist at gmail.com>
a écrit :

>
>
> sent from a phone
>
> On 21. Sep 2018, at 21:32, André Pirard <A.Pirard.Papou at gmail.com> wrote:
>
> The whole cadastral map is offset by that 7m.
> ...
>
> *Picture 3:* So, I dragged his parcel right onto the wall.
> And now it's correctly located, aligned with the fencing all around.
>
>
>
> how did you know which source was off, the cadastral map or the orthophoto?
>
>
> ...
>
> The Belgian cadastre is not the only one with an error shift.
> With JOSM, I have similarly proved that Google Map has a 120m NE shift in
> Beijing.
> Nobody noticed it.
>
>
>
> it is well known that the chinese government requires all imagery and map
> providers to use chinese algorithms which distort the map coordinates
> systematically, in a way that they remain usable as long as your navigation
> system uses the same algorithms.
>
> Ciao, Martin
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