Technology and Equipment
Cam-Era consists of a number of remote sites around the coast of New Zealand connected by modem to a central base station in Hamilton.
Cameras at the remote sites are mounted on poles or on buildings overlooking the monitoring site. Higher mounts have a greater field of view, and give lower resolution for points near to the camera and higher resolution for points far from the camera. The cameras have rain hoods and lens-washers to improve image quality.
Each site must have a power supply, a computer to control the system and a phone connection so that it can communicate with the base station in Hamilton. Some sites have the remote computer housed some distance away from the camera, with a radio link connecting the two.
The basic hardware of the Cam-Era system comprise an Ikegami 1/3 inch colour CCD video camera with a fixed focal length lens (Computar or Fujinon). The lens size is site dependent. The focal length ranges from 6 mm at the Tairua site, to a wide angle 4.5 mm at the Waimakiriri (both cameras), and a closeup 28 mm at Gisborne Port.
At each site the camera is controlled and data processed by a Pentium 200 Mhz computer with a 2 GB hard drive. The operating system is Microsoft Windows NT4. The video board is an Integral Technologies Flashpoint 128 video frame-grabber.
This allows full-speed video to be viewed on the computer screen as well as frame grabbing/storage at rates up to one per second. The video board supplier specifically designed the frame-grabbing program for us. All operations (frame-grabbing, image analysis, transfer of files to our web server) are controlled by a scheduling program called Clockman95 from Graphical Dynamics. This software allows us to control all operations using simple text scripts. We also use pcAnywhere from Symantec to provide full control of Cam-Era computers at each remote site.
We have installed remote wireless links at our new Mokau and Waimakiriri sites. These wireless links operate at 2.4 GHz, sending the video signal via radio from the camera sites to a receiving station up to 5 kms away. Each receiver can handle signals from four camera/transmitters, and the computer controls which channel is viewed. This technology means that we do not have to cable power and phone lines out to the camera location, which is sometimes very inaccessible, and thus save on installation costs. A less expensive version of this technology can transmit lower grade images directly down a modem connection and remove the need for a remote computer.
This technology can also be controlled by other external events, such as only sending images after a certain amount of rain or when an animal triggers a movement sensor. However, at this point the lower-grade image quality is not sufficient for our purposes, although for simple video surveillance, where a lot of analysis is not required, this equipment is ideal.
The site computers are linked to a base station at NIWA Hamilton by modem (2x Dynalink 33.6 K). At the base station the web server and archiving computer is a 200 MHz Pentium with a 10 GB hard drive. The operating system is Microsoft Windows NT4. The images are archived to CD-ROM at six monthly intervals.
Each site computer and its software are easily maintained using remote control software from our desktop at Hamilton. For example, changes can be made to the sampling frequency, and special video capture sequences can be initiated (i.e., for special tides or rectification purposes). Our file transfer protocols have been set up so that, if for any reason the remote computers are unable to connect to the Internet or transfer the files, they are sent at the next available connection time. Problems do occur from time to time with this technology (e.g. disruption of local Internet connection, equipment failure or Telecom line problems). Generally these occur irregularly and the site computers are programmed to continue working; they catch up on file transfer once a connection is re-established. We are advised immediately if a file transfer does not occur, allowing us to investigate problems promptly. The main Cam-Era computer is included in NIWA's standard backup schedule, ensuring all new files are saved daily. Every 4 to 6 months, when the hard drive is full, the images are transferred to CD-ROM (one for each site).