視覚障害者用GPS位置案内装置における測位方式 : SA解除後のDGPSの有効性評価

概要

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We have developed a portable speech-output guidance system for visually impaired people. The system presents place names in spoken format. A GPS (Global Positioning System) is used to identify the place. In order for the system to provide usable access data by blind and low vision users, the measurement error of the GPS receiver becomes critical. Two types of DGPS (Differential GPS) data have been developed to address this problem. These are an FM-DGPS and a radio beacon DGPS, linked to a stand-alone GPS receiver. We evaluate our results in terms of 2drms (twice the distance root mean square). In a measurement of the stand-alone GPS, the error was 11.0 meters without SA (Selective Availability). However, the measurement error was reduced to 6.3 meters for the FM-DGPS and to 3.6 meters for the radio beacon DGPS. This suggests that DGPS is necessary for our system under the situation without SA, and furthermore, that the geographic size of the space within which effective guidance can occur, is a circle with the radius of 6.3 meters. Empirical testing has taken place in urban and suburban areas of Niigata City and on the Niigata University campus. By this testing, we have confirmed that our guidance system using DGPS is useful for the visually impaired.
社団法人日本航海学会の論文
2001-09-25