3

I have some images at a local coordinate system with the following specifications:

TIFF header file: -gdalinfo im.tif

Driver: GTiff/GeoTIFF

Coordinate System is:

PROJCS["Eastern Ridge Project Grid GDA94",
GEOGCS["GDA94",
    DATUM["Geocentric_Datum_of_Australia_1994",
        SPHEROID["GRS 1980",6378137,298.2572221009113,
            AUTHORITY["EPSG","7019"]],
        AUTHORITY["EPSG","6283"]],
    PRIMEM["Greenwich",0],
    UNIT["degree",0.0174532925199433],
    AUTHORITY["EPSG","4283"]],
PROJECTION["Transverse_Mercator"],
PARAMETER["latitude_of_origin",0],
PARAMETER["central_meridian",120.95],
PARAMETER["scale_factor",0.9999],
PARAMETER["false_easting",446904.02],
PARAMETER["false_northing",2879827.84],
UNIT["metre",1,
    AUTHORITY["EPSG","9001"]]]

Origin = (326250.000000000000000,297750.000000000000000)

I want to be able to transform the images to UTM/EPSG:28350 using gdalwarp. I use the following command for this purpose:

-gdalwarp -t_srs EPSG:28350 input.tif output.tif

and

-gdalwarp -s_srs '+proj=tmerc +lat_0=0 +lon_0=120.95 +k=0.9999 +x_0=4 46904.02 +y_0=2879827.84 +ellps=GRS80 +towgs84=0,0,0,0,0,0,0 +units=m +no_defs' -t_srs EPSG:28350 im.tif out.tif

ERROR 1: Translating source or target SRS failed: '+proj=tmerc

When I open the image file in QGIS, it shows that projection is 28350 but coordinates aren't correct and show the previous system as if no transformation has been done. I also put the information above in a text file and used gdalwarp but no luck.

I have two questions:

Are these parameters sufficient to define a projection? If yes, how can use it in gdalwarp or is there any other possible solution?

3

The projection methods commonly used in Australia are Albers equal area, Lambert conformal conic and transverse mercator.

Since the first two need one or two latitudes as parameter, I assume that transverse mercator will fit. UTM uses the same method.

You may take EPSG:3113 GDA94/BCSG02 as an example:

+proj=tmerc +lat_0=-28 +lon_0=153 +k=0.9999900000000001 +x_0=50000 +y_0=100000 +ellps=GRS80 +towgs84=0,0,0,0,0,0,0 +units=m +no_defs

and exchange the parameters with those you have got. Make sure to use decimal degrees for the central meridian. lat_0 seems to be missing, so you might try the equator with +lat_0=0.

Basically, the units could be something else than meters, but this seems to be unusual in Australia.


From the extended information you give, the projection string should be:

+proj=tmerc +lat_0=0 +lon_0=120.95 +k=0.9999 +x_0=446904.02 +y_0=2879827.84 +ellps=GRS80 +towgs84=0,0,0,0,0,0,0 +units=m +no_defs

Your Origin point leads me to a point east of the town named Newman, West Australia.

and the full command line:

gdalwarp -s_srs "+proj=tmerc +lat_0=0 +lon_0=120.95 +k=0.9999 +x_0=4 46904.02 +y_0=2879827.84 +ellps=GRS80 +towgs84=0,0,0,0,0,0,0 +units=m +no_defs" -t_srs EPSG:28350 im.tif out.tif
  • I modified my question to make my question more clear (see above). Are those projection information sufficient for transformation? I appreciate any solution on this. – user2148425 Oct 29 '15 at 10:45
  • Yes, now you have all parameters. Do you get a proj.4 string with gdalsrsinfo? – AndreJ Oct 29 '15 at 11:06
  • This is what I have got from gdal: [ '+proj=tmerc +lat_0=0 +lon_0=120.95 +k=0.9999 +x_0=446904.02 +y_0=2879827.84 +el lps=GRS80 +towgs84=0,0,0,0,0,0,0 +units=m +no_defs ']. I used gdalwarp but no luck yet. – user2148425 Oct 29 '15 at 11:19
  • Does gdalinfo report corner coordinates? Maybe a .tfw file is missing. – AndreJ Oct 29 '15 at 11:26
  • This should show an area in Western Australia. Obviously Newman isn't a correct location. – user2148425 Oct 29 '15 at 11:27
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No. It is not enough, as you don't have projection method. There are multiple possibilities that your central meridian and scale factor can be used to transform coordinates and results will be very different.

  • What do mean by "projection method"? is that the type of transformation like affine, projective etc? What extra information is required? – user2148425 Oct 29 '15 at 2:42
  • you'll need projection for your input dataset if you want reprojection. You can go with affine/polynomial/tps etc. but this won't require projection parameters at all and is a different story. – Maxim Dubinin Oct 29 '15 at 2:56
  • let's focus on rigorous transformation using projection information rather than general mathematical models. You mentioned those parameters I set aren't enough. What other items I have to have to be able to perform transformation? by the way, the local and the target projection use the same datum. Do I need extra parameters in this case? – user2148425 Oct 29 '15 at 4:05

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