By KATIE HAFNER
SAN FRANCISCO, Sept. 4 - On Friday afternoon, Leonard Sprague, a general contractor in Gainesville, Fla., saw the electronic plea.
"I hope someone can help," someone using the name ZuluOne wrote to an online bulletin board. "I am trying to get a current overlay for the area around 2203 Curcor Court in Gulfport, Miss."
Mr. Sprague knew that "current overlay" meant a bird's-eye view. And an altruistic impulse combined with an urge to play with a new technology propelled him into action. Using his PC, he superimposed a freshly available posthurricane aerial photograph over a prehurricane image of the same neighborhood. After 15 minutes, he had an answer.
"Actually, it looks like your house looks pretty good," Mr. Sprague told ZuluOne by e-mail. "Unfortunately, it doesn't look so good for some of your neighbors. Best of luck to you and your family."
In the aftermath of Hurricane Katrina, hundreds of displaced residents and their relatives -- along with people like Mr. Sprague -- have turned to the Internet for information about a home feared damaged or destroyed. Many are using Google Earth, a program available at the Google Web site that lets users zoom in on any address for an aerial view drawn from a database of satellite photos.
By the end of last week, a grass-roots effort had identified scores of posthurricane images, determined the geographical coordinates and visual landmarks to enable their integration into the Google Earth program, and posted them to a Google Earth bulletin board -- the place ZuluOne turned for help.
Most of the images originated with the Remote Sensing Division of the National Oceanic and Atmospheric Administration, which has been posting them to its Web site
Taking inspiration from the online volunteers, Google, NASA and Carnegie Mellon University had by Saturday night made the effort more formal, incorporating nearly 4,000 posthurricane images into the Google Earth database