SANTA ANA --- The government calls them "listers," and hundreds of them have begun to walk the streets of Orange County with handheld computers strapped to their hands, making careful note of every address.

There is, federal officials want to emphasize, nothing to worry about.

The listers are the advance scouts of the 2010 census. Their job is to verify that the Census Bureau's address lists and maps are accurate, so that the census questionnaires that go out next year get to the right places.

Those handheld computers strapped to their hands? They're GPS devices that allow the listers to pinpoint every structure where people live, according to the Census Bureau.

Bureau officials understand that strangers pausing outside a home to tap information into a computer may raise some suspicions. They've notified law-enforcement agencies that their listers are on the job, just in case police start getting calls....