[Talk-us] Proposed import of IBC data (was RE: [Talk-ca] NAD83-SCRS vs WGS84 Reference systems)

Paul Norman penorman at mac.com
Sun Mar 27 19:06:41 BST 2011

Adding talk-us@ and imports@ to the cc list since this touches the border.

The IBC data matches decently with the NAIP and Bing imagery on the border,
and very well with my 10cm Surrey imagery. The existing border data in OSM
is about 20m away in parts (near monument 32 for example)

The proposed tagging is
source=CA-US International Boundary Commission

I don't think it's worth the effort to worry about any NAD83-CSRS vs. WGS84

I've uploaded a sample at http://maps.paulnorman.ca/49th.osm

> -----Original Message-----
> From: Richard Weait [mailto:richard at weait.com]
> Sent: Sunday, March 27, 2011 6:22 AM
> To: Daniel Begin
> Cc: talk-ca at openstreetmap.org
> Subject: Re: [Talk-ca] NAD83-SCRS vs WGS84 Reference systems
> On Sat, Mar 26, 2011 at 3:55 PM, Daniel Begin <jfd553 at hotmail.com>
> wrote:
> > Hi all,
> >
> > I need someone to confirm the following about reference system...
> >
> > Context: Paul and I are uploading US-Canada boundary monuments/turning
> > points to get a stable and verifiable information. The data is
> > available from their web site and I got the confirmation that the data
> > can be used without any restriction.  The data can be found here...
> > http://www.internationalboundarycommission.org/products.html
> >
> > and it is available for NAD27 and NAD83-SCRS reference system.
> >
> > Context: For what I understand, The difference between NAD83-SCRS and
> > WGS84 is 0-2 meters.  To get a rigorous transformation from NAD83-SCRS
> > to WGS84 we need to use shift grids describing the shift between NAD83
> and NAD83-SCRS.
> > These grids should be available through provincial agencies but I have
> > been told that not all provinces have them available.
> >
> > Question1: Do I understand it properly?
> >
> > Question2: Considering that provided coordinates value/reference
> > numbers can be read directly from their web site, it make sense for me
> > to use NAD83-SCRS directly even if there is a 0-2 meter offset.  Does
> > it make sense for everyone?
> Bonjour Daniel!
> We do have others on this list with experience in re-projection.  I hope
> they'll join in.
> I've asked about the shift grids on #osm-dev.
> If I remember correctly, the current Can-US border came from IBC data.
>  How does the current border line match the monument data that you are
> considering?  Should they be identical and are they?  Could we pop this
> data into a tile overlay layer so we can look at it on existing OSM data
> (without the import)?
> Best regards,
> Richard
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