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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