VEHICLE INTELLIGENCE & TRANSPORTATION ANALYSIS LABORATORY     University of California, Santa Barbara

Infrastructure

• Mobile Laboratory.  Our road research vehicle carries equipment for measuring and logging 3-dimensional position and driven distance at any point on the county road network.
• Point/stream Sampling: A laptop computer runs our home-built StreetSmarts software.
• One or more map data bases may be selected at any time
• A Trimble Placer 400 GPS receiver (with CSI MBX3 Coast Guard beacon receiver for differential correction) feeds in vehicle location coordinates at about 1-second intervals.  Coordinates are accurate to about 2 metres.  The vehicle is represented as a dot, its position snapped to the nearest navigable road — currently we have no need/plans to implement intelligent map matching.  The map usually moves with the vehicle, so that the vehicle is always positioned around the center of the screen; or the user may override the auto-centering.  At the user's option, the map may rotate in real time so that the direction of travel is always “up” on the display.  The system may bounce a wireless message to a fixed server, and plot the echoed coordinate, usually a couple of seconds old.
• Given a destination, the system computes the optimal route.  If the vehicle strays from the prescribed path, the route is updated with respect to the current vehicle position.
• Drives can be recorded and played back at variable speed.
• Linear Distance Measurement.  A distance measuring instrument (DMI) counts transmission pulses to measuring distance.  While the resolution of the DMI is 0.1 metre, start/stop spikes of up to 3 metres are possible.
• Mobile Communications.  The vehicle-based laptop may be considered a client, in communication with a remote server.  Messages are passed between the client and server using 2-way wireless communications.  Currently we have deployed Cellular Digital Packet Data (CDPD) modems running at about 19,200 bits per second.  Other less advanced wireless communications technologies — spread spectrum modems (2-way) and FM subcarrier broadcast (1-way) — may be implemented in the future to test specific scenarios.

VITAL's road research vehicle, showing GPS/communications antennae ...	... and interior instrumentation

• Data Bases.  A selection of popular commercial street network data bases was compiled for the County of Santa Barbara.  We sought the participation of all major vendors, especially those operating in California.  The vendors listed below elected to be involved, in full knowledge of our agenda and the nature of our experiments.  We are grateful for their cooperation.
• Etak (Menlo Park CA)
• Geographic Data Technology (Lebanon NH)
• Knopf Engineering Inc (Visalia CA)
• Navigation Technologies (Sunnyvale CA)
• Thomas Brothers (Irvine CA)
• TIGER (U.S. Bureau of the Census)
All map bases were ordered in ArcInfo export format.  Layers were separated as required to consolidate all motorable roads, variously described as freeway, highway, arterial roads, etc, into a single coverage.  The coordinate base was standardized to NAD83 and zone 11 UTM.
 

	Mobile map display with database A (black) and trace of location while driving test vehicle (blue).  Display is centered on current GPS coordinate (blue spot in center of screen) with uncertainty rings of radius 30m and 100m.  Status bar (bottom of display) shows location coordinates (longitude and latitude), street name and address ranges.  Click on thumbnail for full size image.
	Mobile map display with four databases (A, B, D, E) displayed simultaneously.

 
Our experimental agenda is not to rate the quality of the above vendors, individually or comparatively.  It is merely to demonstrate and to test interoperability issues using typical commercially available data.
 
• Server Display.  The server also has access to the street network data bases listed above.  The server can track a fleet of several vehicles, continuously updating their positions on a map display.  Vehicles may report their positions at regular intervals, or the server may petition a particular vehicle for a position report at any time using SAE J2256 message formats 10L and 11L.  A location may therefore be communicated from the server, running map data base A, to the client display running map data base B.  Each message is logged on transmission and receipt, for post-analysis of error.