Argus video monitoring system
This article provides an introduces the video monitoring ARGUS. The article explains why ARGUS has been developed, where it is used and how it works. Also a literature list is provided with all relevant literature about ARGUS.
Until only a few years ago, all information on nearshore morphodynamics had to be gathered from comprehensive field experience. This way of data collection has some fundamental limitations. One problem is the fact that such experiments are relatively expensive and that there is only a limited amount of instrument positions in traditional field experiments. A synoptical pattern is thus difficult to get with the use of a traditional field set up, but this can easily be measured with a shore-based video system. Another and even more important characteristic is the fact that the observation time scale is in practice limited to several weeks. Finally, surveying during severe weather and wave conditions is hardly possible. With the recent advent of new digital imaging technology, shore-based video systems now provide the additional capability of automated data collection, encompassing a much greater range of time and spatial scales than were previously possible.
History and use of ARGUS
The history behind video imaging in nearshore studies probably goes back to the 1930s, where the first attempts to study coastal processes were made with the help of aerial photography. In 1980, developments on video techniques for the monitoring of coastal changes have been initiated by the Coastal Imaging Lab of the Oregon State University, USA. Being continuously improved since 1992, the so-called Argus system nowadays features fully digital video technology which provides high image quality in combination with detailed pixel resolution. Continuous (typically every daylight hour) collection of image data with a resolution of centimetres to meters, extending along regions of hundreds of meters to several kilometres, is now routinely undertaken at sites in the USA, Europe, Australia and Asia.
Since the first automated Argus station was installed at Agate Beach on the Oregon Coast in 1992, the CIL-based program has expanded to 12 locations around the world. Sites were selected to span the parameter space considered relevant to nearshore processes research (ranges in wave period, wave height, tide range and beach slope).
In addition, approximately 30 Argus stations and 120 cameras are now operating daily in 8 countries (see also Figure 2). The greatest acceptance has been in Europe, where Argus technologies are at the heart of the three-year EU CoastView program, and in Australia, where 10 stations are now operating. These stations provide hourly measurements of a variety of topographic, geomorphic and fluid variables and are usually focused on practical Coastal Zone Management (CZM) issues.
An Argus monitoring system typically consists of four to five video cameras, spanning a 180º view, and allowing full coverage of about four to six kilometres of beach. The cameras are mounted on a high location along the coast and connected to an ordinary PC on site, which in turn communicates to the outside world using conventional techniques such as an analogue modems, ISDN, DSL, or a wireless LAN. Data sampling is usually hourly (although any schedule can be specified) and continues during rough weather conditions. As the process of data collection is fully automated, the marginal operating costs are virtually zero.
Each standard hourly collection usually consists of three types of images (Argus image types and conventions). A snapshot image serves as simple documentation of the ambient conditions but offers little quantitative information. Time exposure images average out natural modulations in wave breaking to reveal a smooth pattern of bright image intensities, which are an excellent proxy for the underlying, submerged sand bar topography. Time exposures also ‘remove’ moving objects from the camera field of view, such as ships, vehicles and people. Variance images help identify regions which are changing in time (like the sea surface), from those which may be bright, but are unchanging (like the dry beach).
Plan view, merged images (Argus standard image processing) can be composed by geo-referencing the images from all the cameras of an Argus station. This facilitates the measurement of length scales of morphological features like breaker bars and the detection of rip currents. Besides time-averaged video data, data sampling schemes can be designed to collect time series of pixel intensities, typically at 2 Hz, with which wave and flow characteristics can be investigated.
After collection of different Argus image types (see also Argus image types and conventions), the collected video data can be analysed using the standard Argus analysis software or through dedicated image analysis. At present, ten tools are part of the standard Argus analysis software suite. These are summarised in Table 1:
An eleventh application named argusDesignTool (ADT), that can be applied to design the camera configuration of new Argus stations, is meant for specialized use only.
- Information about coastal imaging
- general information about [www.planetargus.com Argus beach monitoring systems]
- [www.wldelft.nl/argus Argus image archive]
- Introduction of the ARGUS technique]
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