RADAR FINDS ANCIENT RUIN IN CAMBODIA; DISCOVERY THRILLS ARCHEOLOGISTS WHO HAD OVERLOOKED REMAINS.

Byline: David R. Baker Daily News Staff Writer

Training radar on the ruins of an ancient Cambodian city, researchers at NASA's Jet Propulsion Laboratory have found temple remains overlooked by generations of archeologists.

The discoveries, announced Thursday at JPL, offer tantalizing glimpses into the founding of Angkor, a metropolis of 1 million people that flourished between the eighth and 13th centuries. And they demonstrate, once again, airborne radar's ability to peer into the past by spotting buildings, moats and earthworks invisible from the ground.

``You drive right by them - you'd never know they were there,'' said archeologist Elizabeth Moore with the University of London, who had visited Angkor several times before working on the radar survey.

Perhaps the most significant find, a small mound containing the remains of four to six temples, was overlooked for decades, even though it lies in the shadow of Angkor's most famous temple. The mound's ruins, Moore said, suggest that parts of Angkor actually were built 200 to 300 years earlier than previously believed.

``This mound, the temple and the inscriptions on it rewrites the history of Angkor,'' said Moore, head of the university's department of art and archeology.

Researchers' interest in the area was sparked by radar images, taken by the space shuttle in 1994, that showed unidentified ruins in the area, said JPL radar scientist Anthony Freeman.

``It threw up enough challenges to us that we wanted to go back for a closer look,'' he said.

Already, radar had helped spot a long-lost city on the Arabian peninsula, buried for centuries below drifting sand.

At Angkor, the problem was thick vegetation, engulfing the thousands of ruins that dot the countryside. From ground level, the ancient earthworks, if they are visible at all, often look like natural mounds - not the work of a vanished civilization, Moore said.

So in 1996, JPL flew a radar-equipped plane over the area, taking multiple images that could be combined into a three-dimensional map. The map shows perfectly rectangular temples and moats, and circular water reservoirs scattered across about 100 square miles.

The ruins reveal a city that Moore likened to Los Angeles in its obsession with water. The Khmer, the people who built Angkor, created intricate systems for channeling and storing water for the region's dry season.