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Speed Web Cam Technical Information

The speed mesurment device mounted on the web cam is of the LIDAR variety. LIDAR is an acronym for LIght Detection And Ranging. The lidar instrument transmits light out to a target. The transmitted light interacts with and is changed by the target. Some of this light is reflected / scattered back to the instrument where it is analysed. The change in the properties of the light enables some property of the target to be determined. The time for the light to travel out to the target and back to the lidar is used to determine the range to the target. The Lidar unit can operate of a battery pack or an external power source. In this case it's plugged into a charger and will revert to it's internal gel cell in the event of a power failure.

The camera is an older Canon powershot digital camera that is connected view USB to an barebones type PC running Redhat Linux 7.3. The PC is connected to the Internet through a standard PSTN dial on demand connection which is launched when the date changes on the photograph stored in an 'upload' directory. When the Lidar unit detects speed over the preset speed (63 kilometres per hour in this case) the PC forces the camera to take a photograph and the PC moves the photo to an 'upload' folder. The PC then lanches another macro that FTP's the photograph to the web site. Alongside this process the Lidar unit also logs the speed recorded at the time of the photograph into a text file stored on the PC and the speed at the time of the photograph being taken is stripped out using another macro and the text caption below the image displayed on the page is modified.

• View the speed web cam now
• What to do when you see a speeding motorist
• Economic reasons why the privately operated speed camera makes good sense
• Frequently asked questions
• Technical information