On Sat, Jul 19, 2014 at 6:30 PM, Sören Gebbert <[email protected] > wrote:
> Hi Anna, > > 2014-07-19 19:04 GMT+02:00 Anna Petrášová <[email protected]>: > > Hi, > > > > I have a question about Rast3d_location2coord [1]. It is casting the col, > > row, depth values to integer like this: > > > > (int) col > > > > instead of using > > > > (int)floor(col) > > > > as a result, col = 0.1 => col = 0 and col = -0.1 => col = 0, which > doesn't > > seem correct to me. Any opinions? > > I totally agree that there should be a function that returns the row, > col and depth as double values, so the developer can decide how to > handle these values. Otherwise there would be no convenient way to > determine where coordinates are located in the voxel. > > But i am not sure if the integer casting is a bug, since the > Rast_easting_to_col() /Rast_northing_to_row() docs suggest integer > casting as conversion method. There are algorithms in GRASS that use > only integer casting and algorithms that make use of rounding with > floor() before casting to integer. > > The problem arise in case of negative column,row or depth values when > casting to integer without rounding to an integer smaller than the > double number. So the question is are there any chances to receive > negative cols,rows and depths? > > It does not seems do to me for col and row, since in case of negative > coordinates will west and south always be smaller than east and north, > resulting in always positive cols and rows. And the same should be > true for depths, unless the top is smaller than bottom. > Yes, but you still can get negative col, for example when looking for the neighboring voxels of a voxel on the edge of the 3D raster. Then, the inconsistency causes problem. Thanks a lot for implementing Rast3d_location2coord_double. Anna > Best regards > Soeren > > > > > Thanks, Anna > > > > BTW, similar function Rast_northing_to_row from raster library returns > > double. > > > > > > [1] http://grass.osgeo.org/programming7/region_8c_source.html#l00291 > > > > _______________________________________________ > > grass-dev mailing list > > [email protected] > > http://lists.osgeo.org/mailman/listinfo/grass-dev >
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