[OSM-talk] [HOT] Why the HOT obsession with low quality buildings in Africa ?

[Jean-Marc Liotier]

On Tue, July 3, 2018 7:20 pm, john whelan wrote:
> I think my concern is more about the 'then a miracle occurs' in the
> project plan to clean up the buildings.

Yes because, among other reasons:
- For most people, verifying is not as gratifying as creating
- Correcting entirely incorrect geometries is many ways more work than
re-creating them from scratch

I am not concerned about the most egregious cases: cars & trucks modelled
as buildings, duplicates & superposed, rubbish heaps and vague shadows as
building=yes, buildings found in old imagery... Those I delete with no
hesitation.

I am not concerned either about minor simplifications or errors such as
the shape being traced on the roof of the building rather than its base -
those I let them be and correcting them capitalizes on a good foundation.

I am concerned about the cases where a building does exist in reality, the
shape is less than ten meters from its position, some of the shape
overlaps the building's position on the imagery and some of the shape
resembles some of the building. In those cases, there is some value in the
record: approximate position and area of the building. But there is also
the liability of having introduced a low-quality object in the database.

I am convinced that the immense majority of those buildings will never be
corrected. In ten years, we can expect massive campaigns of automated
image recognition to produce new building layers - but even then the
extensive conflation will be an horribly tedious job.

Meanwhile, for areas with reliable imagery, I can imagine Maproulette
jobs: something in the spirit of "Does this building at least partially
overlap one in the imagery and does it approximately resemble the one in
the imagery ?". Those jobs could be designed at national or regional
levels - under control of the local communities. They could be a way of
systematic quality control. But maybe I'm horribly deluded about how many
people would volunteer for such a mind-numbing task. Also, looking at
buildings one at a time is very inefficient compared to panning through an
area on JOSM - but then again, JOSM-enabled contributors that might be
motivated for this are not exactly in plentiful supply either.

And that does not even answer the question: what to do with the
"low-quality  shape but actually exists" cases ? I am at a loss to answer
that.