It used to be there were two ways to estimate a roof: either you climbed up and took measurements by hand, using a tape measure, or you calculated square footage from the ground. The first is risky; neither is always accurate.

Add to these methods a third way: remote roof measurement. Type an address into the computer and, using geocoding, a software program calculates longitude and latitude, enabling a satellite to pinpoint and photograph that particular roof, and then, based on the photograph, to break it down into measurable angles and planes.

The various remote roof measurement programs that are now available supply area and line measurements as well as pitched angle measurements and materials lists. The beauty, say roofers who use remote roof measurement, is that you don't even need to see the property to produce an estimate that's 95% accurate.

Two Squares Over, Two Squares Off

Several companies now offer such a service, including EagleView Technologies

, GeoEstimator and RoofScanIR. Prices per roof report range from $30 to $78, depending on the vendor and the roof's complexity. Roofers say that the service saves time by making repeat visits unnecessary. For instance, what Kasey Dalton Roofing, in South Haven, Miss., used to do, says general manager Lynn Cummings, is to send a salesperson up on the roof. The salesperson would then return to the office to prepare a proposal.

Now salespeople, using EagleView, can prepare the estimate ahead of time and use it in their presentation. Prospects, Cummings says, are "kind of amazed," which helps salespeople close.

Jeff Petrucci, owner of Bloomfield Construction, in Bloomfield Hills, Mich., started using GeoEstimator in March, and describes himself as being amazed by its accuracy. "It gives you exact square footage," he says, and it is particularly useful on steep slopes. He downloads the GeoEstimator 10-page report and submits it to prospects with his proposal.

Accuracy is especially important to Sutherland Exteriors, in Concord, N.C., since 99% of the company's roofing jobs now involve insurance claims, where there is less flexibility if the estimate is inaccurate. "If it's a 30 square roof and we asked for 26 squares, then the process of going back and asking for the extra squares becomes quite lengthy," general manager Jason Alexander says.

Right now Alexander estimates that the company is using EagleView on 80% to 85% of its jobs, and uses 98% to 99% of the materials ordered for the job.

EagleView CEO Chris Barrow says that the company's report is routed through a series of technicians for checking. If it's off by 5% or more, he says, it's free.

An accurate estimate also allows for some peace of mind when it comes to ordering. "If your distributor's closed Saturday and Sunday," Alexander says, "you can have confidence that you'll get the job done and not have to leave the roof open all weekend."

Leaving the Stone Age Behind

Roofing contractors who use remote roof measurement find that it makes hand-measuring a roof seem Stone Age by comparison. The challenge is figuring out how to integrate the service into their selling process.

For instance, Sigma Exteriors, a home improvement company in Milwaukee, Wis., started using aerial imaging last year. Office manager Perla Callaway says that the company's eight reps usually visit the house first, then decide ? sometimes after using Google Earth to check the complexity of the roof ? whether or not to order an EagleView report.

Sigma Exteriors reps must work fast because generating a report typically takes 24 to 48 hours, and the company's reps have 72 hours after their initial consultation to get a proposal into the prospect's hands.

Others point out that a bird's-eye view of the roof, via technology, must also be augmented by personal inspection. "I still go out to the house, meet with the owner, and get in the attic," Petrucci says. "You need to feel the plywood, the valleys and saddles, see if there's rotten siding. It's not going to change what I do, but it will save me time and risk."

Alexander adds that his company doesn't automatically order a report for every one of the 750 leads that the company generates per month. "Once we make a presentation and they agree to allow us to work with their insurance company, we come back and order EagleView."