[Qgis-user] Using CRS to convert from Lat Long to Irish National Grid

[Carson Farmer]

Hi Kurt,

Unfortunately, I think you may have misinterpreted what 'on the fly
projection' and 'set layer CRS' are for. Your layer's CRS should be
set to whatever the coordinates are actually measured in, and if your
layers are indeed in lat/long (probably WGS84), then this should stay
that way. If you change the project CRS to Irish National Grid (are
you sure you want IRENET95/Irish Transverse Mercator? When I work with
Irish data I usually use TM75 /Irish Grid [EPSG code: 29903]), then
turn on 'on the fly projection', things should just line up (assuming
you have the layer CRSs defined correctly). If you're concerned about
it, you can also right click on a layer and select save as... to
export to a new projection (but again, this assumes you have the
initial CRS correctly defined. Do the layers that you are using have
.prj files associated with them, if yes, then QGIS *should*
automatically pick up the correct CRS, so no need to 'set layer CRS'
at all.

HTH,

Carson

On Tue, Mar 27, 2012 at 7:14 PM, Kurt Springs <ferret_bard at mac.com> wrote:
> Hi Folks,
>
> I'm in a bit of a pickle.  I am preparing some maps for a grant proposal and wanted to add some good vector maps for lakes and oceans.  The problem is these vector maps are in latitude/longitude and I need to convert them to Irish National Grid.  I tried using v.proj in GRASS but ran into problmes (and that is a different list group anyway).  After searching the internet I discovered CRS.
>
> I made sure properties was set to IRENET95/Irish Transverse Mercator and checked Enable 'on the fly' CRS transformation.  Then I right clicked the vector layer and selected "Set Layer CRS" and set it, again, for IRENET95/Irish Transverse Mercator.  If I accept what is there already as right, all the lakes wound up in South America.  It looks like the lat/long numbers didn't convert over.  Is there a way to manually move them into position and make it away that this is it's right and proper position under IRENET95/Irish Transverse Mercator?
>
> Thanks for any help.
>
> Kurt D. Springs
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-- 
Dr. Carson J. Q. Farmer
Centre for GeoInformatics (CGI)
School of Geography and Geosciences
Irvine Building, University of St Andrews
St Andrews, Fife, KY16 9AL
Scotland, UK