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

[Daniel Begin]

Thank Paul, a really good idea to include others as they are concerned :-)

About tagging, I would agree with minor adjustments ...
man_made=survey_point - agreed

ref=xxxx - agreed to reference a monument id
However, I would add a prefix for turning points, helping differentiate them
from monuments. I propose the prefix "tp ": ref=tp 123 

source=CA-US International Boundary Commission - Make sense but...
I think we could replace the source tag for the website tag. It would then
point directly to the file, and the source, from witch the coordinates were
retrieved...

Example:
website=http://www.internationalboundarycommission.org/coordinates/HallsStre
am.htm

website=http://www.internationalboundarycommission.org/coordinates/Highlands
.htm

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

What do you think about that?

Best regards,
Daniel


-----Original Message-----
From: Paul Norman [mailto:penorman at mac.com] 
Sent: March-27-11 14:07
To: 'Richard Weait'; 'Daniel Begin'
Cc: talk-ca at openstreetmap.org; talk-us at openstreetmap.org;
imports at openstreetmap.org
Subject: Proposed import of IBC data (was RE: [Talk-ca] NAD83-SCRS vs WGS84
Reference systems)

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
man_made=survey_point
ref=32
source=CA-US International Boundary Commission

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

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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