## You didn't provide a constructor from a file
## But you could have.
my $grid = Seismic::Grid->new( 'seismic.dat' );

for my $line_id ( $grid->line_ids ) {
    my $line = $grid->get_line( $line_id );
     
    for my $stn_id ( $line->station_ids } ) {
        my $station = $line->get_station($station_id);
        
        $station->set_Easting( 
            $station->get_Easting 
            - ( $station->get_Easting * 0.00001 ) 
        );
        $station->set_Northing( 
            $station->get_Northing 
            - ( $station->get_Northing * 0.000002 ) 
        );
        $station->set_Elevation( 
            $station->get_Elevation() - 1
        );

        ## You didn't provide this attribute, presumably 
        ## cos like me you didn't know what is was        
        ## but you could have
        $station->set_Other(
            int(
                ( $station->get_Easting()
                * $station->get_Northing()
                * $station->get_Elevation()
            ) / 3.0
        );
    }
}