[Talk-ca] NAD83-SCRS vs WGS84 Reference systems

[Richard Weait]

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