[ros-users] how to use sonar to navigation?

Hi,

My robot is Pioneer 3, but I have not the laser sensor, for that Hokuyo and
SICK sensors are way out of reach for us. So I want to use sonar to make
SLAM and then make navigation. And I want to find an existed package to
achieve our goal, but it seems that it almost pretty much requires the usage
of a laser for SLAM and navigation. So how can I begin my work to use sonar
to achieve SLAM and navigation. Is there any examples to help me?

By the way, I have studyed the amcl package several times, But I still don't
know where Publisher the topic "scan" or "base_scan", that's to say, where
the laser data comes from?
Any help will be appreciated! Thanks in advanced!
jolin