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

[Kurt Springs]

Hi Carson,

Interesting.  I switched to TM75.  Then I imported the lakes and ocean from the shape files and they just snapped in place.  I was trying to do it from GRASS.  When I tried to set them to the rest of the GIS they vanished until I returned them to their original CRS.  That was almost too easy.

Next question.  I am putting my vectors into a spatialite database through qspatialite.  Will the lakes and oceans behave themselves if I use them in a different project or shift the project to a different computer?  Like as not it will still be TM75.  BTW, thanks for the info.  IRENET95/ Transverse Mercator seemed to be the only logical candidate.

Again, Thanks.

Kurt
On Mar 27, 2012, at 3:39 PM, Carson Farmer wrote:

> 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