[gdal-dev] Re: Can't get gdalwarp to create a raster in Mercator-2SP projection?

[Patrick Sunter]

Oops, sorry sent message accidentally without last bit of text output,
pls see below ...

On Thu, Sep 29, 2011 at 11:38 AM, Patrick Sunter <patdevelop at gmail.com> wrote:
> Hi,
>
> As part of testing GDAL's NetCDF drivers projections, I've been trying
> to gdalwarp a Geotiff file from a UTM projection to Mercator-2SP
> (http://geotiff.maptools.org/proj_list/mercator_2sp.html).
>
> Thinking I should file this as a ticket? But thought I'd post here first.
>
> I've tried 2 approaches to specifying the target SRS as Mercator-2SP,
> and in both cases the resulting files comes out as Mercator-1SP:
>
> 1) Specifying using Proj4 (the 'lat_ts' paramater specifies a std
> parallel and differentiates from Mercator-1SP
> gdalwarp -t_srs '+proj=merc +lat_ts=-45 +lon_0=145 +x_0=0 +y_0=0
> +ellps=WGS84 +datum=WGS84 +units=m +no_defs' melb-small.tif
> savedResults/Melb_USGS/refactored_gdal/melb-small_M-2SP.tif
>
PROJCS["unnamed",
    GEOGCS["WGS 84",
        DATUM["WGS_1984",
            SPHEROID["WGS 84",6378137,298.257223563,
                AUTHORITY["EPSG","7030"]],
            AUTHORITY["EPSG","6326"]],
        PRIMEM["Greenwich",0],
        UNIT["degree",0.0174532925199433],
        AUTHORITY["EPSG","4326"]],
    PROJECTION["Mercator_1SP"],
    PARAMETER["central_meridian",145],
    PARAMETER["scale_factor",1],
    PARAMETER["false_easting",0],
    PARAMETER["false_northing",0],
    UNIT["metre",1,
        AUTHORITY["EPSG","9001"]]]


>
> 2) Specifying the full requested OGC WKT:
> gdalwarp -t_srs 'PROJCS["unnamed", GEOGCS["WGS 84", DATUM["WGS_1984",
> SPHEROID["WGS 84",6378137,298.257223563, AUTHORITY["EPSG","7030"]],
> AUTHORITY["EPSG","6326"]], PRIMEM["Greenwich",0],
> UNIT["degree",0.0174532925199433], AUTHORITY["EPSG","4326"]],
> PROJECTION["Mercator_2SP"], PARAMETER["central_meridian",146],
> PARAMETER["standard_parallel_1",-45],
> PARAMETER["latitude_of_origin",0], PARAMETER["false_easting",0],
> PARAMETER["false_northing",0], UNIT["metre",1,
> AUTHORITY["EPSG","9001"]]]' melb-small.tif
> savedResults/Melb_USGS/refactored_gdal/melb-small_M-2SP.tif
>
> Resulting gdalinfo projection section:
>
PROJCS["unnamed",
    GEOGCS["WGS 84",
        DATUM["WGS_1984",
            SPHEROID["WGS 84",6378137,298.257223563,
                AUTHORITY["EPSG","7030"]],
            AUTHORITY["EPSG","6326"]],
        PRIMEM["Greenwich",0],
        UNIT["degree",0.0174532925199433],
        AUTHORITY["EPSG","4326"]],
    PROJECTION["Mercator_1SP"],
    PARAMETER["central_meridian",146],
    PARAMETER["scale_factor",1],
    PARAMETER["false_easting",0],
    PARAMETER["false_northing",0],
    UNIT["metre",1,
        AUTHORITY["EPSG","9001"]]]

So it seems GDAL is falsely converting both requested translates to
Mercator-1SP?

thanks, Patrick.