[gdal-dev] NetCDF config option for west > east?

[Even Rouault]

On samedi 24 novembre 2018 23:09:34 CET Markus Metz wrote:
> I have created a PR for this, but there are still issues:
> 
> is
> Pixel Size = (0.099999991285714,-0.100000004000000)
> Corner Coordinates:
> Upper Left  ( -25.0000122,  69.9999970)
> Lower Left  ( -25.0000122,  29.9999954)
> Upper Right (  44.9999817,  69.9999970)
> Lower Right (  44.9999817,  29.9999954)
> Center      (   9.9999847,  49.9999962)
> 
> should be
> Pixel Size = (0.100000000000000,-0.100000000000000)
> Corner Coordinates:
> Upper Left  ( -25.0000000,  70.0000000)
> Lower Left  ( -25.0000000,  30.0000000)
> Upper Right (  45.0000000,  70.0000000)
> Lower Right (  45.0000000,  30.0000000)
> Center      (  10.0000000,  50.0000000)

Yes, the issue is that the data type for the x variable in the .nc file is 
float32, so it has not enough precision. You could try to round the coodinates 
with some heuristics, like (untested !)

for the resolution:

double K = std::pow(10, 4 - std::round(std::log(res) / std::log(10)));
if( std::fabs(K * res - std::round(K * res)) < 1 )
{
	res = std::round(K * res) / K;
}

for the coordinates:

// Case where coordinates are aligned on a multiple of the resolution
if ( std::fabs(x / res - std::round(x / res)) < 1e-3 )
{
    x = std::round(x / res) * res
}
// Case were they are aligned with a half-pixel shift
else if (std::fabs((x - res/2)/res) - std::round((x - res/2)/res)) < 1e-3 )
{
    x = std::round((x - res/2)/res) * res + res/2;
}


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