[Qgis-user] New dialog when opening layer with a different CRS

[Saulteau Don]

That's so a user can apply datum transformations from one coordinate
system to another (ie, NAD27 <-> NAD83 <-> NAD83(CSRS)). They are
usually compiled into Proj4 through grid shift binary files (.gsb)
often available from federal or provincial and local agencies.

For example, in British Columbia, a lot of data comes in EPSG:26910
(UTM Zone 10N / NAD83) or EPSG:3005 (BC Albers / NAD83).

But converting either of those to EPSG:3153 (BC Albers / NAD83,CSRS)
which uses the Canadian Spatial Reference Standard/System requires a
custom "transformation" that can only be applied when using NTv2 grid
shift files. Or old NRCAN Atlas of Canada data can come in a Lambert
Conformal Conic projection in the NAD27 datum.

This is a long awaited feature and I'm very excited for it! This way I
don't have to drop back to command line to do my vector data
transformations.

http://webapp.geod.nrcan.gc.ca/geod/tools-outils/index.php
ftp://ftp.gdbc.gov.bc.ca/pub/world/NTv2.0
http://forums.arcgis.com/threads/4267-Custom-transformation-nad83-to-nad83-CSRS-for-British-Columbia




SaultDon



On Fri, Jan 3, 2014 at 2:38 AM, Lene Fischer <lfi at ign.ku.dk> wrote:
> Hi,
>
> Using QGIS weekly.
>
> When I open a new layer with a different CRS I get a dialog “Select datum
> transformations for layer ..”
>
> I´ve already set “Enable on the fly” –
>
> Just clicking OK it works- but I don´t understand this dialog – can anyone
> help for an explonation?
>
> Regards
>
>
>
>
>
>
>
> Lene Fischer
>
> Associate Professor
>
>
>
> Department of Geosciences and Natural Resource Management
>
> University of Copenhagen
>
>
>
> MOB +45 40115084
>
> lfi at ign.ku.dk
>
>
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>
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