[gdal-dev] different results for vector and raster datareprojections

[nimalika fernando]

Hi,

Thank you for the support

I couldn’t solve the issue yet

Please note that I have  redone the work with updated SL99 information.
Still I have the same issue.

Earlier I have used projection parameters in the ogr2ogr command and this
time

the WKT based on a projection file which I am using regularly is used.

Detailed information is as follows



The content of the file :

SL99 WKT



PROJCS["SL_grid_99",

GEOGCS["GCS_Kandawala",

DATUM["D_Kandawala",

SPHEROID["Everest_1830",6377276.345,300.8017]],

PRIMEM["Greenwich",0],UNIT["Degree",0.017453292519943295]],

PROJECTION["Transverse_Mercator"],

PARAMETER["False_Easting",200000.000],

PARAMETER["False_Northing",200000.00],

PARAMETER["Central_Meridian",80.77171],

PARAMETER["Scale_Factor",0.9999238418],

PARAMETER["Latitude_Of_Origin",7.00048],

UNIT["Meter",1]]



Following command is used to project the vector data

ogr2ogr -a_srs slgrid99.wkt F:\UDAdata\test\cmc_b_sl99.shp
F:\UDAdata\test\cmc_bound.shp



Raster data’s original projection information is as follows ( from gdalinfo)



PROJCS["UTM Zone 44, Northern Hemisphere",

    GEOGCS["WGS_1984",

        DATUM["WGS_1984",

            SPHEROID["WGS 84",6378137,298.2572235630016],

            TOWGS84[0,0,0,0,0,0,0]],

        PRIMEM["Greenwich",0],

        UNIT["degree",0.0174532925199433],

        AUTHORITY["EPSG","4326"]],

    PROJECTION["Transverse_Mercator"],

    PARAMETER["latitude_of_origin",0],

    PARAMETER["central_meridian",81],

    PARAMETER["scale_factor",0.9996],

    PARAMETER["false_easting",500000],

    PARAMETER["false_northing",0],

    UNIT["Meter",1],

    AUTHORITY["EPSG","32644"]]



Then I have used the following command to re-project raster data.



gdalwarp -t_srs slgrid99.wkt -s_srs "+proj=utm +zone=44 +ellps=WGS84
+datum=WGS84 +units=m" F:\UDAdata\po_310491_rgb_0000000_Clip.img F:\

UDAdata\test\raster_sl99.tiff



Then , when over layering I use the following custom projection in QGIS. It
worked fine with different vector data in the local context. This is the
first time I’m using raster data in my work.



+proj=tmerc +lat_0=7.00047 +lon_0=80.77171 +x_0=200000 +y_0=200000
+ellps=evrst30 +to_meter=0.999924 +units=m



The shift is around 200m.



WKT of the re projected files are as below

Vector

PROJCS["SL_grid_99",

    GEOGCS["GCS_Kandawala",

        DATUM["Kandawala",

            SPHEROID["Everest_1830",6377276.345,300.8017]],

        PRIMEM["Greenwich",0],

        UNIT["Degree",0.017453292519943295]],

    PROJECTION["Transverse_Mercator"],

    PARAMETER["False_Easting",200000.000],

    PARAMETER["False_Northing",200000.00],

    PARAMETER["Central_Meridian",80.77171],

    PARAMETER["Scale_Factor",0.9999238418],

    PARAMETER["Latitude_Of_Origin",7.00048],

    UNIT["Meter",1]]



Raster

PROJCS["SL_grid_99",

    GEOGCS["GCS_Kandawala",

        DATUM["unknown",

            SPHEROID["unnamed",6377276.345,300.8017000000115]],

        PRIMEM["Greenwich",0],

        UNIT["degree",0.0174532925199433]],

    PROJECTION["Transverse_Mercator"],

    PARAMETER["latitude_of_origin",7.00048],

    PARAMETER["central_meridian",80.77171],

    PARAMETER["scale_factor",0.9999238418],

    PARAMETER["false_easting",200000],

    PARAMETER["false_northing",200000],

    UNIT["metre",1,

        AUTHORITY["EPSG","9001"]]]



Any clarification would be much appreciated.



Thanking you

nimalika
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