[gdal-dev] Precission problem with atof

Jorge Arévalo jorge.arevalo at gmail.com
Wed Jul 22 19:01:59 EDT 2009


Context: GDAL WKT Raster Driver

While creating the Dataset, I execute this query:

SELECT srid, ST_AsText(extent), pixelsize_x, pixelsize_y, blocksize_x,
blocksize_y FROM raster_columns WHERE r_table_name = 'table' AND
r_column = 'rast'

I have loaded a 3-band tiff file with gdal2tiles. Its pixel size is
0.9. If I execute this line (over the result of the previous query):

 fPixelSizeX = atof(PQgetvalue(hPGresult, 0, 2));

I get 0.899999976158142 instead of 0.9.

The string obtained wiht PQgetvalue is "0.9", but, for any reason,
atof transform this string in 0.899999976158142.  So, seems to be a
precission problem. think the string used by atof has any problem, but
I'm not sure. Oh, if I execute double f = atof("0.9") f is 0.9000002
(obtained in gdb).

What should I do? I tried to change atof(nptr) for strtod(nptr,
(char**)NULL), but it didn't work...

Thanks in advance

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