[OSM-talk-be] WMS (aerial) imagery covering Belgium, now conveniently packaged for adding it to JOSM

Tue Jan 6 10:47:57 UTC 2015

Well, up to today, all the work is being done by AGIV. The municipalities can report issues with the database, it still is AGIV that sends out a contractor to do the mapping. And we always check 10% of the work our contractors bring in. Hence, the quality should be pretty much equal all over Flanders.

Now in the future, the municipalities will be able to do their own mapping. They can send in as-built plans after construction works (public domain, not houses), those plans will be integrated in the GRB.

Indeed, new houses are not yet fully mapped. A surveyor can of course not enter private terrain to map the back side of houses. So they map the front and add 5 meters to create the shape. We are currently updating those houses based on aerial mapping. In the future we will no longer release those half-mapped houses (people call them “garageboxen”). We have new aerial images every year, the houses will be released only when fully mapped.

And indeed, mapping houses is a lot easier in rural areas than in urban areas. Building layouts can be complicated and the only indications our mappers have is what’s visible form the air (of course in combination with what was visible to the surveyor in the street). Perhaps a guesstimation sometimes looks better, but still what you see on the GRB is what is seen on aerial images. It could be that reality is more complex than a guesstimation. I’m not saying it all is perfect, but things like projection distortion should be rather exceptional, since they’re mapped with a stereo photo mapping technique.

Cheers,
jan

From: Stijn Rombauts [mailto:stijnrombauts at yahoo.com]
Sent: maandag 5 januari 2015 21:29
To: OpenStreetMap Belgium
Subject: Re: [OSM-talk-be] WMS (aerial) imagery covering Belgium, now conveniently packaged for adding it to JOSM

Even in het Nederlands als ik mag.

De gemeentes zijn verantwoordelijk voor 'hun' GRB. Ik vermoed dat alle gemeentes de opbouw van hun GRB uitbesteed hebben aan landmeters. Misschien dat updates (zie bv. https://www.agiv.be/news/2014/december/update-grootschalig-referentiebestand-20-12-2014) door de gemeentes zelf aan het GRB worden toegevoegd. Maar het is dus perfect mogelijk dat de kwaliteit in de ene gemeente minder is dan in een andere gemeente. Maar ze zouden eigenlijk toch allemaal moeten voldoen aan de eisen die door AGIV zijn opgelegd.
De gebouwen in het GRB zijn gebaseerd op topografische opmetingen op terrein en op luchtfoto's. Waar mogelijk zijn de voorgevels opgemeten: die zouden dus behoorlijk correct moeten zijn. De rest is gebaseerd op de luchtfoto's. Zo krijg je soms vreemde toestanden van recente gebouwen waarvan de voorgevel is opgemeten, maar het achterliggende stuk grotendeels ontbreekt omdat ze niet op de luchtfoto's staan/stonden. De huizen in Beekstraat 55-61 zijn waarschijnlijk zo'n geval.

Groetje,

StijnRR

________________________________
From: Marc Gemis <marc.gemis at gmail.com<mailto:marc.gemis at gmail.com>>
To: OpenStreetMap Belgium <talk-be at openstreetmap.org<mailto:talk-be at openstreetmap.org>>
Sent: Monday, January 5, 2015 8:23 PM
Subject: Re: [OSM-talk-be] WMS (aerial) imagery covering Belgium, now conveniently packaged for adding it to JOSM

I assume the quality depends on the GIS person adding the data. If he/she is less motivated/less capable/... the quality will be less.

The example that you give seems like the classic case where the building was not yet finished when it was traced. Then they always draw a small rectangle along the front side.

regards

m

On Mon, Jan 5, 2015 at 7:56 PM, Sander Deryckere <sanderd17 at gmail.com<mailto:sanderd17 at gmail.com>> wrote:

I think Pablo also helped in some pieces of the GRB: http://www.geopunt.be/kaart?viewer_url=http%3A%2F%2Fmaps.geopunt.be%2Fresources%2Fapps%2FGeopunt-kaart_app%2Findex.html%3Fid%3Dff8080814a6e1332014abb6b94c80023
Is it normal that quality differs from municipality to municipality? In Staden, I haven't seen any problem with GRB. But in Roeselare, I often bump into problems like these. Buildings with a completely clear form (however, they're often quite new, so perhaps drawn without aerial pics), but drawn completely wrong in GRB.
Up until now, I've avoided the old centre of the town, because the building layouts are way too complicated there. It might get easier when we have access to the GRB.

So yes, an automated import won't work, but being able to use it opens up a lot of perspectives, so thanks to anyone involved.
Regards,
Sander

2015-01-05 15:35 GMT+01:00 Gilbert Hersschens <ghersschens at gmail.com<mailto:ghersschens at gmail.com>>:

In comparison to Bing even Picasso wins ;-)

On 5 January 2015 at 15:30, Glenn Plas <glenn at byte-consult.be<mailto:glenn at byte-consult.be>> wrote:

In my experience, the outlines and building shapes I've seen in GRB are
like 10 times better than all the work that exists using bing and other
sources.

A one on one copy would be silly, but if you bring it all together,
agiv/grb and osm data, it helps to make sense of what you are looking
at. Also it is conclusive usually when new buildings replace older.
It's the best source, I don't really care if the house isn't exactly as-is.

The housenumber inports will take years, but it's fine as it is as tons
of intelligent choices and conclusions, mistakes and other uglynes needs
to be fixed too. And it all helps, if you overlay them with some
transparacy adding GRB would be an awesome tool.

I've been doing housenumer entries for weeks now, grb layer would
defenitely be of good help.  But never a dumb copy.

Glenn

On 05-01-15 15:05, Gilbert Hersschens wrote:
> Guys,
>
> Don't get overly exited about the building shapes. The quality of those
> shapes is quite variable. For free standing houses they are OK - in some
> cases even excellent, but for urban areas they are not very useful,
> certainly not as a source for import. I have been using those shapes for
> quite a while for comparison in cases where severe projection distortion
> and strong shadows gave me a hard time to figure out the shape of a
> particular building and in many cases the shapes in GRB were not better
> or even worse than my own "guesstimation".
> They're OK for "second opinions" but I would never use a tool to import
> those shapes.
> Just my 2 cents.
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