On 30-06-2017 21:21, Jochen Topf wrote:
On Fri, Jun 30, 2017 at 08:16:40PM +0200, Frank Steggink wrote:
Maybe I'm not understanding it, but in the OSM inspector [1] I just see one
case of old style multipolygon, in Manitoba. Last week, when you posted your
original message, I just saw one case in New Brunswick. IIRC, it was a park,
not even from the Canvec import.
The types of problems I am talking about don't show up in the OSM
inspector. This is not old-style multipolygons (where tags are on the
outer ways and not on the relation), but multipolygons where the tags
are on the relation AND on the ways.
Ah, ok, now I understand. Since there was a lot of discussion about old
style multipolygon tagging, and since this type of problem hasn't been
added to OSM inspector, this wasn't immediately obvious.
In the OSM inspector other errors can be seen, but the most prevalent one is
"Touching rings". Maybe indeed a case of suboptimal mapping, but nothing
which seems urgent to me.
Here is an example of a forest multipolygon, imported by me
(canvec_fsteggink). It is still version 1, but it has tags on the relation,
not on the rings (except for the quarries): [2]
This is from Canvec v7.0. IIRC, we started at v6.0, and the last version I
know of is v10.0. Maybe v6.0 had wrong tagging, but I'm not seeing any such
cases in the OSM inspector.
So, I'd like to ask you to give a couple of examples where data imported
from Canvec is clearly wrong with regard to old style multipolygon tagging.
Here are all cases in Canada (not only those from the imports):
https://tmp.jochentopf.com/954226a3acab882d28d8500ddef8203d/same-tags-ca.pbf
Here is one example where you can clearly see the problem:
http://www.openstreetmap.org/relation/541821
How difficult would it be to add this to OSM inspector? Not everybody
has Postgres running, and is able to use osm2pgsql. Yes, there is
documentation, but it requires some technical skills. Also, it would be
very convenient to have this updated daily.
When we have clear examples, then it might be easier to come up with a plan
how to fix it. But so far, I see absolutely no reason why Canada stands out
in a negative way. Yes, we all acknowledge that Canvec data is suboptimal,
but as others already have pointed out, mapping everything by hand in
especially remote areas is nearly impossible.
Canada stands out in a negative way, because
a) there are so many problems. Nearly a third of the cases worldwide are in
Canada and
b) most of these problems are probably caused by one little program, the
program used to convert/import the CanVec data.
As you might have noticed, later imports, like the example I provided,
don't have that issue anymore. I'm mentioning this to express that not
_all_ Canvec data is at fault! Only the first couple of versions.
However, for some reason this was never noticed up until a point that
collaborative action was done to have it fixed. Probably because the
rendering pipeline of the slippy map was accepting this kind of tagging
up until recently.
Mapping Canada "by hand" might be difficult because it is such a huge
country and there aren't that many mappers. But the same arguments goes
for why you have to be extra careful importing data. If you break
something, there are not enough people to fix it manually. And, yes,
errors do happen. And if we find them, we fix them and move on. But
errors from imports can be so huge there aren't enough people there to
fix them manually.
The world is so huge that there aren't enough people to create and
maintain a global world map. However, OSM exists. Fixing errors can also
be crowdsourced. Martijn van Exel is really doing a great job with
MapRoulette, for instance. Although fixing errors (cleaning up the mess
left behind by others) is not nearly as rewarding as mapping, it might
be easier to do, especially since there is no need for a lot of
creativity when fixing the same kind of errors.
So I think it is the job of those who did the import
in the first place, to fix their work. If you add data to OSM you take
on a certain responsibility. If you add more data, you have a larger
responsibility.
The person who did most work initially on the Canvec import has already
left OSM about five years ago. This was during the license change. He
joined one of the forks, from which we hear nothing nowadays. So, don't
count on him, and possibly not on others who were working on the Canvec
import at that time. I'm sure he and others who were involved at that
time regret certain decisions being made and actions being done.
However, the import was supported by the majority of the community at
that time, and although there are people who have criticized the import
(and also of the Geobase roads) they still exist in OSM and are
gradually being improved by others.
But saying: We don't have the manpower, so we are taking
a shortcut and then, when it turns out the shortcut wasn't so short
after all, whining that you don't have the manpower to fix it. That
can't be the excuse.
I'm not using it as an excuse, but as a fact. I don't know how
"complete" the Canadian map is, but I'm sure that it will be way less
complete when imports wouldn't have been done. I recall that one day
I've driven about 800 kms, for about 12 hours in total, but the
resulting GPX file doesn't look that "impressive". It barely made a
dent, even at that time... Just a couple of main roads and some
adjustments in the database. The same applies to digitizing, or as it is
also called, "armchair mapping".
Personally, I think that, although things were far from perfect, they
were done with the best intentions and with the support of the majority
of the Canadian OSM community. We have to deal with this situation now.
A much more cooperative tone would have been very welcome, especially
since you would like to see us coming off our lazy butts and fix our mess.
There is really nothing to gain by threatening to contact the DWG in
order to have those imports removed. They already exist for about 7
years! And if the Canadian community at large wouldn't have welcomed it,
this would have come to the surface way sooner. So, why has this
suddenly become such a huge problem because of the way how the slippy
map is rendered?
We can much better focus on getting the job done, than criticizing each
other. If 150 people are fixing 100 multipolygons each, this is doable!
We could do it with the help of OSM inspector, and eventually a
MapRoulette task.
Jochen
Frank
p.s. Are you still wearing your t-shirt with Lake Manicouagan on it,
based on OSM data? I hope it doesn't contain wrong tagging or imported
data. ;)
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