Ok, I kind of fix it putting a function giving only the first character of the reference in template-functions.php:
`if($exif['EXIFGPSLatitudeRef'] == 'S'){ $lat = '-' . $lat; }
if($exif['EXIFGPSLongitudeRef'] == 'W'){ $long = '-' . $long; }`
replaced by:
`if(substr($exif['EXIFGPSLatitudeRef'],0,1) == 'S'){ $lat = '-' . $lat; }
if(substr($exif['EXIFGPSLongitudeRef'],0,1) == 'W'){ $long = '-' . $long; }`