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I georeferenced a .tif image (image 1) using QGIS software following the Irish Grid System [EPSG:29903]. After I georeferenced. I see that the image shape is changed (image 2).

Image 1 enter image description here

Image 2 enter image description here

Then I checked the georeferenced image with gdalinfo command and obtained the following output.

Driver: GTiff/GeoTIFF
Files: 3_thin.tif
Size is 10786, 11223
Coordinate System is:
PROJCS["unnamed",
    GEOGCS["Modified Airy",
        DATUM["unknown",
            SPHEROID["mod_airy",6377340.189,299.3249373654824],
            TOWGS84[482.5,-130.6,564.6,-1.042,-0.214,-0.631,8.15]],
        PRIMEM["Greenwich",0],
        UNIT["degree",0.0174532925199433]],
    PROJECTION["Transverse_Mercator"],
    PARAMETER["latitude_of_origin",53.5],
    PARAMETER["central_meridian",-8],
    PARAMETER["scale_factor",1.000035],
    PARAMETER["false_easting",200000],
    PARAMETER["false_northing",250000],
    UNIT["metre",1,
        AUTHORITY["EPSG","9001"]]]
Origin = (315183.331350925960578,233504.650853214989183)
Pixel Size = (0.034052782164520,-0.034052782164520)
Metadata:
  AREA_OR_POINT=Area
Image Structure Metadata:
  INTERLEAVE=PIXEL
Corner Coordinates:
Upper Left  (  315183.331,  233504.651) (  6d16'13.91"W, 53d20'21.26"N)
Lower Left  (  315183.331,  233122.476) (  6d16'14.41"W, 53d20' 8.91"N)
Upper Right (  315550.625,  233504.651) (  6d15'54.07"W, 53d20'20.98"N)
Lower Right (  315550.625,  233122.476) (  6d15'54.57"W, 53d20' 8.62"N)
Center      (  315366.978,  233313.564) (  6d16' 4.24"W, 53d20'14.94"N)
Band 1 Block=10786x1 Type=Byte, ColorInterp=Red
Band 2 Block=10786x1 Type=Byte, ColorInterp=Green
Band 3 Block=10786x1 Type=Byte, ColorInterp=Blue

I would like to know, when the output upper left coordinates as 315183.331, 233504.651, does it point A or point a' ? (A and a' are marked in red color in image 2).

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I understood that it's point A and not a'. I used, Irish Grid Referencer website and manually entered the coordinates to see it by myself.

Resulted image is pasted below: enter image description here

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  • Right. Gdalinfo reports the corner coordinates from the outermost corners of the corner pixels.
    – user30184
    Commented Mar 24, 2021 at 18:33
  • @user30184, thanks, do you know how to produce GeoTiff images without the black color borders. I need to use these images in an application, hence having black color borders is not effective.
    – 0xMinCha
    Commented Mar 24, 2021 at 18:47
  • If you want that the image is north-up then no. Raster images are rectangular, filled with pixels allover. You can select the color that you want to use for filling the areas which lack the real image data. You can make application to show this fill color as transparent. For example in QGIS go to raster properties and set black as transparent. Or you can create an alpha band of mask band and utilize that for setting transparency.
    – user30184
    Commented Mar 24, 2021 at 19:15

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