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Redrawing the Lines : New Mapping Systems Promise Accuracy, Headaches


Your local grocery store isn't where you think it is.

At least, it probably isn't where the map says it is. Most property and geographic boundaries in the U.S. were drawn using surveying methods dating from the 18th century. Now the combination of the computerized mapping technologies known as geographic information systems, or GIS, and a newly available satellite navigation system developed by the military is raising the possibility that a new map of the country will have to be drawn.

"You may think you're buying 41.75 acres, but in reality what you may have is 39.25 acres," said Brett Lane, the surveyor of Clark County in Las Vegas.

Computer mapping software--essentially creating the electronic versions of existing maps--has been around for nearly a decade. But the Clinton administration's announcement last month that it will make the Pentagon's global positioning system, or GPS, fully available for commercial use is transforming a cottage mapping industry into what administration officials predict will become an $8-billion behemoth.

The GPS system, composed of 24 satellites, makes it possible for anyone with a hand-held receiver to determine his or her location (accurate within 50 feet) anywhere on the planet. Mapping software coming out now from companies such as Redlands-based ESRI and MapInfo Corp. in Troy, N.Y., are designed to take advantage of this newly available GPS information. And a recent directive to release topographical data gathered from government satellites promises to make geographic analysis even more exact.

"We need to make geospatial data . . . available not just to commercial enterprises but to anyone in the world with a computer," Interior Secretary Bruce Babbitt said at a GIS conference in Palm Springs last month.

The new technologies will make it possible for the first time to survey land in increments as small as an inch. And the redrawn boundaries that result could affect everything from property taxes to utility rights-of-way to flood insurance policies.

Clearly, in most cases, small changes in property boundaries won't have a significant effect on taxes. But in some situations, the tax implications of redrawing long boundary lines could be substantial.

"Taking 2 feet down the line off a property isn't a big deal. On the other hand, if I have 300 acres that used to belong to the federal government that is now someone's private property, then that could have a real tax impact," said Bob Wilson, assistant chief executive of Orange County.

Tax assessments are only one of a host of potential implications of applying GIS technology to existing maps, according to executives in the emerging GIS industry. Insurance companies could apply the technology to determine more exactly where flood plains begin and end, and set their coverage for individual policy owners accordingly.

Because the Interior Department is using GIS to help manage wildlife resources, property owners will now have more reliable information with which to petition the government in matters of land management, such as whether their land falls under the auspices of the Endangered Species Act, according to Jim Dorsey, a land and boundary consultant in Palm Springs.

"You'll never be able to completely replace the land survey. But this is a great boon for property owners because it lowers the cost of surveying the property. Plus, you increase your chances of finding something about your property that's been missed or overlooked," Dorsey said. "Using GIS technology, you can split a gnat's eyebrow."

Also, property owners will be able use the technology to avoid hitting forgotten or incorrectly mapped underground gas and telephone lines--a common scourge of construction projects. Pacific Bell is in the initial stages of using GIS to map its statewide deployment of fiber-optic cable. For the first time, the phone company will have a database and maps marking the exact locations of all its underground wiring. Other utilities are expected to do the same.

"With GIS, you realize that you don't own what you own. Title insurance is supposed to cover resulting problems for private landowners. But we have to actually clean up the problem for ourselves," said Sean Curry, GIS project manager at Pacific Bell in San Ramon, Calif.

Some expect the new geographical surveys carried out by GIS or GPS systems to eventually have a sweeping impact, although it will be about five years before the best GPS data will be available.

"Coastlines will end up shorter than we thought; shopping malls will find themselves on government property. People in industry know about this, but they don't want to talk about it because they have no idea how to handle the problem," said John Pemberton, president of the Pemberton Group, a Marshfield, Mass.-based consultancy specializing in GIS technology.

But others see much less cause for alarm. "To the extent that someone's property lines aren't right, then there will have to be [governmental] action," Orange County's Wilson said. "But I don't want to think there will be a wholesale redrawing of property lines."

Ilan Greenberg, an editor at Infoworld Magazine, can be reached at

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