| 摘要 |
PURPOSE:To reduce the time required for searching a corresponding map or enlarged map by a system wherein an area held between inter-record gaps (IRG) for indexing is determined as one block on a magnetic tape, and map informations on one original and one enlargement of a displayed map are recorded as one set of map informations in said block. CONSTITUTION:A magnetic tape has such recorded areas as a soundless IRG signal portion IRG1, an enlarged-map position information portion D1 provided additionally with an information on a matrix position at which an enlargement of the original map is inserted, i.e. the data showing the position number of the IRG signal portion on the right or left on the tape, to which said enlargement is adjacent, an original-map data portion M1 in which the map data for one picture are recorded, an enlargement data portion LM1 in which the map data on the enlargement for one picture are recorded, and another soundless IRG signal portion IRG2. The area held between the IRG signal portions IRG1 and IRG2 in this way is determined as one block. Thus, the two data on the original map and the enlargement thereof can be made to correspond to one IRG signal respectively, and a desired number of enlargements are inserted between the original maps without disturbing the regularity of the original maps. This constitution enables the high-speed retrieval of the original of the displayed map and the enlargement thereof which are necessary for a navigation system, and consequently a time required for retrieval of a map can be reduced. |
