[Talk-ca] CanVec data to OSM

[James Ewen]

> On 1/24/11, Dan Charrois <dan at syz.com> wrote:

>> I did a little test import in my area (083H13), which seemed to work well.

Howdy neighbor! (I'm in 083H11)


>> To be sure I wasn't adding duplicate features, I only added the categories
>> for features which didn't already exist in the area (waterway=stream,
>> natural=wood, etc.).  We already had good road network data for the area,
>> which has been available for some time, and has been tweaked since, so I
>> definitely didn't want the Canvec data to override that.

Actually, keep your eyes open for issues there. Before GeoBase data
was available, there were a number of ways that roads got into the
database. The initial work was very crude, with major highways just
being lines in somewhat the right area. A few of us drove around
gathering GPS traces, and brought some of those roads closer to
reality. Some of the secondary highways, along with the backroads were
traced off low resolution imagery. They can be a little bit out of
alignment.

When User:GeoBaseStevens did the mass import of road data for Alberta,
the routines he used tried to keep from overwriting existing user
contributions. As such, there are some roads out there that can be
quite a bit out from reality, and even more that are closer, but still
not quite right. A few, like a section of highway 43 from Onoway to
Whitecourt has been peeled up, and not replaced. If you are playing in
the area, and notice things missing or out of alignment, feel free to
peel and replace.

During a mass import, it was felt that it was important to not blindly
erase all user input, and replace with GeoBase data. However, if you
are manually looking at the data, and making an informed decision to
replace one set with another, that should be acceptable. Check the
existing ways for tags that might not be in the CanVec data.

Also be aware that there are a lot of errors that were introduced by a
User:vreimer. There are highway label tags on roads that aren't
highways, duplicate label tags, and other errors such as that. Clean
those us as you find them please.


>>  A few situations
>> like natural=water took much more effort since we already had data available
>> for the large lakes, but not smaller ones.  Not wanting to remove the OSM
>> data already in place, and wanting to avoid duplications with the Canvec
>> data, I went through and did a fair bit of manual editing to make sure I was
>> only adding data for new features, not changing existing ones.

Again, the major lakes were probably traced out by a script called
LakeWalker. It used aerial imagery to try and find the edge of lakes.
Due to the quality of imagery available, some lakes weren't quite
accurate. I have poked at some to fix the obvious errors, but most of
that is done using the same low resolution imagery. I've done a bit of
water import (see around Bonnyville), and would use the same criteria
as for replacing roads. If the existing water is less accurate than
what you have, peel and replace.

Most of what was done previously was done with low quality source
data, and it was inserted into the database to simply get "something"
onto the blank screen.

I did some forest imports around Bonnyville, but find that the roads
dissappear into the trees because the grey for roads is not much
different in contrast to the green for the trees. I also ran into an
issue with OSM not liking the number of points I was trying to import
at once as well...


>> Thanks for your help!  I look forward to getting more involved in continuing
>> to add to the OSM resource!

Thanks for joining the OSM community... we need more hands and eyes on
Alberta... there aren't a lot of us poking around the map up here,
especially outside of the big cities.


>> Syzygy Research & Technology
>> Box 83, Legal, AB  T0G 1L0 Canada
>> Phone: 780-961-2213

Hey, aren't you a Pfranc distributor? I've been to your house!

James
VE6SRV