#untested
for ($n=0;$n<=$#lat;$n++) {
    for ($v=0;$v<=$#lat;$v++) {
        if ( abs( $lat[$n] - $lat[$v] ) < .01 and abs( $long[$n] -  $long[$v] ) < .01 )  {
            ##OTHER CODE   
        }
    }
}