I like this! The only thing I might change is the bit mentioning the satellite imagery. I think it also has roots in air photos from the NTS work.
Cheers! --G On Wed, Aug 31, 2016 at 10:24 PM, Sam Dyck <samueld...@gmail.com> wrote: > Here's my suggestion for a sort of FAQ (in wiki markup), incorporating > what James already wrote. I'm posting it here for comment because I have a > tendency to get unhelpfully passive aggressive. > > The squared off sections of forest in Canada are the result of unfinished > CanVec data import. CanVec tiles are broken up into squares called the NTS > grid to better manage the data. If you see a forest that's squared off with > a empty section beside it, it's most likely that that grid has not been > imported yet. > > ''What is Canvec?'' > > [[Canvec]] is a digital product produced by the federal government that is > a combination of various federal geodata databases into 1:50000 tiles. > These tiles were converted by Natural Resources Canada into OSM XML and put > on a government FTP server for importation into OSM. After several years of > licensing discussion. > > ''Some of the data in a Canvec import changeset has something weird going > on (forests overlapping in lakes, islands where there don't appear to > islands, wetlands where there sohuld be lakes). Why are you importing this > garbage?'' > > Canvec is generally accurate, it was collected from high quality satellite > imagery collected for the federal government, and has generally withstood > our attempts to ground truth it. However there are errors and apparent > errors. Some of these can be explained by natural changes: lakeshores shift > with the years and seasons, lakes become wetlands, forests burn or are cut > down and regrow. > > The simple reason we have to do this import is because Canada is enormous > and has very few people, consequently there are large areas that have a > very light human presence. For example the territory of Nunavut, the > largest subnational division in Canada, is larger than of France, Ukraine, > Sweden and the United Kingdom combined and has less than 40,000 people. > Most people in Canada live in a handful of cities a short distance from the > US border. There is a lot of blank area to fill, and so we make an effort > to import quality data, but there is a lot of area to cover, so after long > discussions we arrived at the consensus that importing Canvec data was the > best solution, providing we followed a set of practices. > > ''Don't you have local mappers in these communities who could check the > data?'' > > Most likely no. See the note about population density above. Also much of > non-urban Canada, especially Northern communities, have to rely on > satellite internet, which is both extremely expensive and has both > effective download speeds measured in kbps and small data caps of 5 or 10 > GB. > > ''I see some issues with Canvec data, what should I do?'' > > If you think the data itself is in error, try and check to see if it could > not possibly be an accurate reflection of what might be at some point. > Canvec importers have been criticized for importing data, that while it > looks suspicious, accurately reflects what is on the ground. If it's an > obvious error that's easy to fix, go ahead and correct it. If there's > something bigger, talk to the mapper or post on the talk-ca mailing list. > > ''I see something wrong with the actual structure of the data (overly > complex ways, duplicate ways).'' > > These should have been fixed in the import, but sometimes things get > missed. Please go ahead and fix them. > > ''I found a Canvec import that didn't comply with the import policy!'' > > Please don't revert it, despite the appearance of wholesale importing, a > proper Canvec import takes a lot of time and effort on the part of the > importer. Canvec imports began before the current import policy, and so > some importers continued what they had already been doing unaware of the > policy. Hopefully everyone is in compliance now, but if you do see > importing incorrectly please assume good faith. > > _______________________________________________ > Talk-ca mailing list > Talk-ca@openstreetmap.org > https://lists.openstreetmap.org/listinfo/talk-ca > >
_______________________________________________ Talk-ca mailing list Talk-ca@openstreetmap.org https://lists.openstreetmap.org/listinfo/talk-ca