[Qgis-user] problems with georeferencing results

Tue Oct 25 15:42:43 PDT 2011

Ok, i got it.
The reason it doesn't work is probably easily explained: the source X/Y are
considered as raster space coordinates, while I thought that having the
raster a CRS assigned this was kept into account during the warping.
Probably manual re-georeferencing is conceptually unuseful, outside my
exercise. Even if reprojection wasn't enough, the best way would be to
remove any CRS reference from it.
Tomorrow I will do more tests, but I'm pretty sure that I was simply trying
a wrong procedure...

giovanni

2011/10/26 G. Allegri <giohappy at gmail.com>

> Sure Baren, this was just an exercise ;)
> I wanted to test regeoreferencing a raster and compare manual
> georeferencing against reprojection.
> I'm wondering if manually regeoreferencing an already georeferenced raster
> can break things...
>
> Inviato da dispositivo mobile
> Il giorno 25/ott/2011 22.43, "Barend Köbben" <kobben at itc.nl> ha scritto:
>
> Hi Giovanni,
>>
>> I don't understand: you want to change a projected raster (in CRS 3003) to
>> another projection (23023), so why do you need the georeferencing plugin?
>> The data is already referenced, so it sounds to me you just want to
>> re-project it, using the Raster > Warp menu.
>>
>> Or am I missing something...?
>>
>> Yours,
>>
>> --
>> Barend Köbben (Senior Lecturer)
>> ITC - University of Twente, Faculty of Geo-Information
>> Science and Earth Observation
>> PO Box 217, 7500AE Enschede (The Netherlands)
>> +31-(0)53 4874 253
>>
>>
>>
>> On 25-10-11 21:23, "G. Allegri" <giohappy at gmail.com> wrote:
>>
>> >Thanks for the reply.My raster infos are:
>> >
>> >PROJCS["Monte Mario / Italy zone 1",
>> >    GEOGCS["Monte Mario",
>> >        DATUM["Monte_Mario",
>> >            SPHEROID["International 1924",6378388,297.0000000000014,
>> >                AUTHORITY["EPSG","7022"]],
>> >            AUTHORITY["EPSG","6265"]],
>> >        PRIMEM["Greenwich",0],
>> >        UNIT["degree",0.0174532925199433],
>> >        AUTHORITY["EPSG","4265"]],
>> >    PROJECTION["Transverse_Mercator"],
>> >    PARAMETER["latitude_of_origin",0],
>> >    PARAMETER["central_meridian",9],
>> >    PARAMETER["scale_factor",0.9996],
>> >    PARAMETER["false_easting",1500000],
>> >    PARAMETER["false_northing",0],
>> >    UNIT["metre",1,
>> >        AUTHORITY["EPSG","9001"]],
>> >    AUTHORITY["EPSG","3003"]]
>> >Origin = (1554747.231034494200000,4924790.769999999600000)
>> >Pixel Size = (100.000000000000000,-100.000000000000000)
>> >Metadata:
>> >  AREA_OR_POINT=Area
>> >Image Structure Metadata:
>> >  INTERLEAVE=BAND
>> >Corner Coordinates:
>> >Upper Left  ( 1554747.231, 4924790.770) (  9d41'17.95"E, 44d28'24.73"N)
>> >Lower Left  ( 1554747.231, 4678290.770) (  9d39'49.22"E, 42d15'14.92"N)
>> >Upper Right ( 1771747.231, 4924790.770) ( 12d24'49.32"E, 44d25'28.44"N)
>> >Lower Right ( 1771747.231, 4678290.770) ( 12d17'30.22"E, 42d12'31.70"N)
>> >Center      ( 1663247.231, 4801540.770) ( 11d 0'50.84"E, 43d20'53.55"N)
>> >Band 1 Block=2170x1 Type=Float32, ColorInterp=Gray
>> >  Min=-3.876 Max=2051.503
>> >  Minimum=-3.876, Maximum=2051.503, Mean=152.789, StdDev=265.873
>> >  NoData Value=0
>> >  Metadata:
>> >    STATISTICS_MINIMUM=-3.8761155605316
>> >    STATISTICS_MAXIMUM=2051.5034179688
>> >    STATISTICS_MEAN=152.78946158147
>> >    STATISTICS_STDDEV=265.87340110007
>> >
>> >
>> >As you can see the CRS is correctly defined, and the other metadata are
>> >correct.
>> >OTFR works fine, the raster is correctly reprojected on the 23032
>> >reference.
>> >No tfw or aux files in the same folder....
>> >
>> >It's making me crazy!
>> >giovanni
>> >
>> >
>> >2011/10/25 Richard Duivenvoorde <rdmailings at duif.net>
>> >
>> >On 2011-10-25 19:04, G. Allegri wrote:
>> >> Here it is the GCP list picture: http://bit.ly/suh5UL
>> >> (I wonder why ths srcY coordinates are shown as negative values)
>> >
>> >
>> >What is projection of your raster, is it really epsg:3003 (to be tested
>> >with 'gdalinfo yourraster'.)
>> >
>> >Is there maybe a tfw file hanging around which determines another extent
>> >four your source raster? If seen this behaviour recently while using the
>> >plugin.
>> >
>> >Try to set your tiff aside from other files, create a fresh epsg:23032
>> >project with 'on the fly' and try again?
>> >
>> >Hope this helps.
>> >
>> >Regards,
>> >
>> >Richard Duivenvoorde
>> >
>> >
>> >
>> >
>> >
>>
>>
>> Faculty of Geo-Information Science and Earth Observation (ITC)
>> University of Twente
>> Chamber of Commerce: 501305360000
>>
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