[Qgis-user] vector shp from NAD83 (CSRS98) to UTM WGS84

[Neumann, Andreas]

Hi Nicolas and André, 

To be honest I don't know much how you setup QGIS properly to use the
grid shift files. I just wanted to say that the support is there, but
probably needs some improvements or better explanation/documentation. 

For my own country's date shifts, "it just works", probably because the
configuration is already built into QGIS because the grid-shift support
was developed for a Swiss customer. The only thing I had to do is to
download the grid shift file and place it in share\proj. 

It may well be that to make it easier to use grid shift files for the
average user, there should be improvements in the way the grid shift
files are organized and used in QGIS. Having to create a custom
projection is not very user friendly. 

Maybe it would also be more user friendly, if QGIS would already deliver
the grid shift files for most countries. But that would bloat QGIS quite
a bit. The grid shift file for Switzerland (one of the smallest
countries in the world) is already 3 MB. Maybe a grid shift file manager
and repository would help for downloading, installing and deleting the
files and for setting it up properly for easy usage. 

So if you have proposals how to improve, please bring them up. 

Andreas 

On 2016-04-01 08:48, Andre Joost wrote:

> Am 01.04.2016 um 08:12 schrieb Andre Joost: Am 31.03.2016 um 16:55 schrieb Nicolas Cadieux: Hi Andreas,
> That is very interesting. I would like to know more about these grids
> and how QGIS deals with it.  Do you have any additional links to
> share?
> All I can see is that the proj4 parameters for many of the CRS in
> North America are identical and lead to no actual changes in the
> coordinate unless you are going from nad27 to nad 83 or Wgs84 which is
> more drastic.
> That is why I use the nrcan tool that can do transformation based
> on  ITRF and WGS84 CRS.
> I would be nice to do that strait in QGIS. I will look into your
> method and report back. 
> QGIS already uses a grid shift file internally for the conversion from
> NAD27 to WGS84. But there is not yet any grid shift file that reflects
> newer tectonic moves, like NAD83(CSRS98) would need.

Update: You might find some grid file resources in the following
document:

<http://downloads2.esri.com/support/TechArticles/Grid-based_Transformation_Methods_for_Canada3.pdf>

HTH,
André Joost

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