data reader based on :class:`altimetry.tools.nctools.nc` object.
        
        .. note:: THIS can be VERY powerful!

def read_nc(self,filename,**kwargs):
        '''
        data reader based on :class:`altimetry.tools.nctools.nc` object.
        
        .. note:: THIS can be VERY powerful!
        '''
        
        #Set filename
        self._filename = filename
        
        remove_existing = kwargs.get('remove_existing',True)
        
        #Read data from NetCDF
        obj=nctools.nc(verbose=self.verbose,limit=self.limit,use_local_dims=True)
        outStr=obj.read(filename,**kwargs)
        
        #Remove attributes already existing in data object
        for a in self.__dict__.keys():
            if outStr.has_key(a) and not a.startswith('_') :
                if remove_existing :
                    outStr.pop(a)
                    self.message(2, 'Attribute {0} already exists - removing it (set remove_existing to False instead)'.format(a))
        
        return outStr