[Talk-ca] Fwd: RIP CanVec

[Adam Martin]

Oops, meant to reply to the list, not an individual. :)


---------- Forwarded message ----------
From: Adam Martin <s.adam.martin at gmail.com>
Date: Mon, Nov 17, 2014 at 7:43 PM
Subject: Re: [Talk-ca] RIP CanVec
To: Alan Trick <alantrick at gmail.com>


I have had some experience regarding the use of Canvec data. I have not
tried to import this data myself nor would I try - it is complex enough
that I think it is better that I keep my fingers out of it. My experience
with Canvec has been limited to correcting the data in areas that I am
editing in.

I echo the statements of Ga Delep in part - the data, in some areas, has
been haphazardly imported with features out of alignment and possible
destruction of user contributed data. But on the balance, I think it has
been a good information source in the hands of experienced importers. Land
features, such as local hills, groves, open landscapes, reefs ... these are
excellent pieces of information for the map. It has it's issues - the tiled
nature of the data is one problem. Another is the enormous multipolygon
relations that result from imports of these areas - they are difficult to
modify and correct because of the large size. They might be inaccurate when
one compares them to the fine details, but they serve the purpose when
there is no other data available. Honestly, I destroy these polygons when I
encounter them AND I am in the process of correcting the data where they
exist

Ensuring the data remains available to these handful of skilled individuals
is a good idea, as is ensuring that the community is consulted with the
data is being imported.

On Mon, Nov 17, 2014 at 7:27 PM, Alan Trick <alantrick at gmail.com> wrote:

> I don't think the two of you are actually disagreeing at all. Ga Delap
> just said that the past importers of CanVec data were too haphazard and
> that there was not enough community consulting. It seems like the quality
> of the data in Quebec might have been worse than in other places too.
>
> (Désolé, je ne parle pas francais bien.) Je ne pense pas que vous
> differez. Ga Delap a dit seulment que les ancients importateurs de donne
> CanVec etiez trop négligé est ils n'agissent pas avec la communauté. Il me
> semble aussi que la qualite de donne quebequois est pire que les autres.
>
> On Mon, Nov 17, 2014 at 2:00 PM, Dan Charrois <dan at syz.com> wrote:
>
>>
>> > On 2014-Nov-17, at 1:53 PM, Ga Delap <gadelap at gmail.com> wrote:
>> >
>> > Il y a actuellement un peu de bruit sur talk.ca pour faire renaître les
>> > importations CanVec.
>> > Il ne faut pas.
>> >
>>
>> Unfortunately, though I can read French, I can only speak or write
>> English properly, but wanted to weigh in on this discussion.
>>
>> As someone who has imported a fair bit of Canvec data, I wanted to weigh
>> in on this.
>>
>> Though Canvec data has some issues involved in importing into OSM that
>> people should be aware of, I think that it does far more good than harm if
>> treated properly.  All data from Canvec (or any source for that matter)
>> should be inspected carefully before importing into OSM - using satellite
>> imagery for verification, for instance.  And in particular, any data from
>> Canvec that is replacing existing data in OSM should be considered very
>> carefully and with a high degree of suspicion, as in most cases (though not
>> all), our existing OSM data is superior.
>>
>> But with that said, there are a lot of pieces of data from Canvec that we
>> don't have in OSM and should be added - more streets, addresses, and forest
>> areas, as you mentioned - especially if they're verified by overlaying
>> satellite imagery.  I'd add to that list hydrography.  In particular,
>> smaller streams and lakes in my part of Canada tend not to exist at all in
>> OSM, and adding them from Canvec adds data where there otherwise was none.
>> It's usually best to leave the larger lakes and rivers that already exist
>> alone, though perhaps adding a bit more detail to their shorelines.
>>
>> In my experience, probably about 90% of the data in Canvec (particularly
>> non man-made features) that is not already in OSM may be worth importing.
>> And similarly, about 90% of the data that is common between the two is best
>> left alone.
>>
>> Some areas of the map in more remote areas don't have any data at all in
>> OSM - in those cases, importing Canvec data particularly adds a huge amount
>> of value.  In places like downtown Toronto, probably not so much.  I think
>> Canvec data is very valuable for OSM and very strongly support its
>> continued importation, under the condition that whomever is doing it knows
>> some of the issues as you pointed out to ensure they are always making
>> things better instead of worse.
>>
>> Dan
>> ---
>> Dan Charrois
>> President, Syzygy Research & Technology
>> Phone: 780-961-2213
>>
>>
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