American and British cartographers, long aware of the falsification of key features on Soviet maps, rejoiced today at the prospect that they might get a more accurate picture of Soviet geography. [ Page 4. ] Mr. Yashchenko said the willingness to put out reliable maps reflected the policy of Mikhail S. Gorbachev, the Soviet leader, calling for greater openness and a relaxation of what Mr. Yash-chenko called ''mistrust and spy mania.''

The falsification of Soviet maps, Mr. Yashchenko told Izvestia, began in the late 1930's when the map-making administration was put under control of the security police, then known as the N.K.V.D.

''Even in the post-Stalin time the distortion of generally available maps continued as a requirement of the work of our administration,'' he said. ''This work became senseless with the appearance of space photography,'' which meant foreign countries could make their own extremely accurate maps from satellite data. ''But nevertheless it continued until this year,'' he said.

''The correct maps were classified, practically without exception,'' Mr. Yashchenko added.

Even public maps of very imprecise scale, he said, such as 40 miles to the inch, were distorted. On more detailed maps, he said, ''almost everything was changed.''

''Roads and rivers were moved,'' he said. ''City districts were tilted. Streets and houses were incorrectly indicated. For example, on the tourist map of Moscow, only the contours of the capital are accurate.''