Differential GPS with accuracy gradable for certain participants

摘要

DGPS data obtained from an FM broadcast wave is extracted by a DGPS data extraction section (226). Adjustment error, the accuracy of which is not very high, has been appended to correction data to be used in actual positioning correction within the obtained DGPS data. A correction value creation section (228) judges, from the contents of DGPS data, which data in a correction value table (230) may be read. The method of this judgment is predetermined. Then, the correction value is created by reading the corresponding correction value from correction value table (230). Next, the correction value and correction data are added in a DGPS data specifying section (232) to yield proper correction data. Position information having high accuracy can be obtained from the obtained proper correction data. Subscribers can thus be ranked according to the accuracy of positioning for which they are prepared to pay. IMAGE