System Description
Since 1993, we have developed 3 versions of the PGS. Version 1 has been described in our earlier publications. Version 2 was implemented in May 2000 and consisted of a lightweight PC/104-based CPU system carried in a totebag with a shoulder strap. The components were an Advanced Digital Logic PC/104 166MHz Pentium CPU board, a Toshiba 6 MB hard drive, a Scidyne GPIO-104 multi I/O PC/104 module, a Garmin GPS25-LVS 12-channel GPS receiver, an Etak solid state magnetic sensor for sensing head orientation, Diamond Multimedia PCI sound card, a PC/104 to PCI adapter card, and a stereo headset. All component boards were plugged together on a PC/104 bus forming a stack 4 ½"(w) x 5"(l) x 4 ½"(h). The dimensions of the totebag, which contained all the components, was 6 ½"(w) x 11"(l) x 7 ½"(h).
The GPS receiver provided the user's position with an accuracy of 15 m RMS. Although the receiver was differential-capable, differential correction was not used. The receiver module was 1.8"(w) x 2.75"(l) x 0.45"(h) and was located inside the computer carrying case. It was connected to the computer via a serial port. The GPS antenna was a lightweight box 2 3/4"(l) x 2"(w) x ¾"(h) and was mounted above the user's shoulder by attaching to the computer carrying case shoulder strap. The 2 1/4"(w) x 2 1/4"(l) x ¾"(h) magnetic sensor was used as a solid-state compass and was attached to the top of the user's headset as a head-direction sensor. The sensor outputted two analog voltage signals which were interfaced to the computer via the multi-I/O card. The entire system was powered by a 12v lead-acid rechargeable battery located inside the carrying case.
The PNS customized software application consisted of a data base of the UCSB campus in DXF format, Microsoft SAPI 4.0 speech recognition and text-to-speech engines, DirectX 8 DirectSound 3d virtual auditory display, and a custom speech-recognition, menu driven, and console-based combination user interface
Version 3, which is the current version, is much bulkier and heavier than Version 2 because we wanted hardware with higher reliability and a GPS receiver with higher precision, in order for us to conduct experimental research on the user interface. The new version consists of a Toshiba Protégé 7200 notebook computer, Trimble AG-114 12-channel differential GPS receiver, Honeywell HMC 2003 magnetic sensor, Measurement Computing PCM-DAS08 PCMCIA Multi-IO card, and a stereo headset. The PNS software application consists of a data base of the UCSB campus in DXF format, Microsoft SAPI 4.0 speech recognition and text-to-speech engines, DirectX 8 DirectSound 3D virtual auditory display, and a custom speech-recognition, menu driven, and console-based combination user interface
The GPS receiver provides the user's location with submeter accuracy and utilizes the Omnistar differential service. The receiver consists of a 5 ½" diameter x 4" tall dome type case which is mounted atop a 36" mast attached to a waist pack. It is connected to the computer via a USB port and is powered by a 1.2 AH 12v lead acid rechargeable battery. The 1" x 1" x 1 ¾" magnetic sensor is used as a solid-state compass to provide heading information and can be attached to the user's headset as a head-direction sensor or mounted on a hand-held pointer (like a Talking Signs© receiver). In some display modes, auditory information is provided via a small amplified loudspeaker attached to the over-the-shoulder carrying strap of the computer.