[Qgis-developer] Shapefile: prj vs qpj (CRS info)

[Luiz Motta]

Hi Benoit,

I created a new shapefile by QGIS with same CRS of Town (EPSG 32630).

The QGIS created two files of projections: PRJ and  QPJ.

The PRJ have the same value of yours (Town.prj) but the QPJ don´t have
same value (see below):

1) Default -PRJ :

PROJCS["WGS_1984_UTM_Zone_30N",GEOGCS["GCS_WGS_1984",DATUM["D_WGS_1984",SPHEROID["WGS_1984",6378137,298.257223563]],PRIMEM["Greenwich",0],UNIT["Degree",0.017453292519943295]],PROJECTION["Transverse_Mercator"],PARAMETER["latitude_of_origin",0],PARAMETER["central_meridian",-3],PARAMETER["scale_factor",0.9996],PARAMETER["false_easting",500000],PARAMETER["false_northing",0],UNIT["Meter",1]]

2) Create by QGIS - QPJ :

PROJCS["UTM Zone 30, Northern Hemisphere",GEOGCS["WGS
84",DATUM["WGS_1984",SPHEROID["WGS
84",6378137,298.257223563,AUTHORITY["EPSG","7030"]],TOWGS84[0,0,0,0,0,0,0],AUTHORITY["EPSG","6326"]],PRIMEM["Greenwich",0,AUTHORITY["EPSG","8901"]],UNIT["degree",0.0174532925199433,AUTHORITY["EPSG","9108"]],AUTHORITY["EPSG","4326"]],PROJECTION["Transverse_Mercator"],PARAMETER["latitude_of_origin",0],PARAMETER["central_meridian",-3],PARAMETER["scale_factor",0.9996],PARAMETER["false_easting",500000],PARAMETER["false_northing",0],UNIT["Meter",1]]

The QGIS read CRS only by QPJ value.

You can put this value(QPJ) inside in PRJ file for work with QGIS.


The questions is:
Why, QGIS have two different values for "WKT CSR"  for same EPSG 32630 ?
One for PRJ other for QPJ



2011/3/1  <benoit-3 at bc-consult.com>:
> Hi Paolo,
>
> Please see attached zip file (small 2KB file)
>
> It contains:
> - A point shapefile with its CRS set to WGS84 UTM30N (prj file only) and a
> single point (located over the town of Kumasi in Ghana)
> - A QGIS project in Google Mercator CRS.
>
> When you load the shapefile into the project and then use the google plugin
> to display the satellite image around the point you could note that the
> satellite image is not what you expect (if you know the area).
> Also, double click the shapefile layer and go to the General tab. The CRS is
> set to Google Mercator, not UTM30N.
>
> Quit QGIS, rename the prj to qpj and do the above process again, and all is
> correct now.
>
> I hope you can reproduce this behaviour.
>
> Regards,
> Benoit
>
>
>
> On Tue, 01 Mar 2011 12:13:03 +0100, Paolo Cavallini <cavallini at faunalia.it>
> wrote:
>>
>> Il giorno mar, 01/03/2011 alle 12.59 +0200, Tim Sutton ha scritto:
>>
>>> I tested with a shp that I use in training courses I give. For me if I
>>> rename the qpj, the prj is still recognised correctly.
>>
>> Just checked: a shp with a prj, no qpj is recognized and reprojected
>> correctly.
>> Could you please share the shp that gives you trouble?
>> All the best.
>
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