Field Observation Techniques, State of the Art 2012
Contents
Introduction
Observation of coastal areas may address very different aspects of the environment such as parameters and processes of water quality, hydrodynamics, geomorphology, meteorology and ecology. Observing objects requires sensors, including different oceanographic instruments. Observations can be done in situ, i.e. at the location of the observed object, by deploying the sensor / instrument to the water or by inline measurement techniques (flow-through systems). Data recording can be done by using buoys, moorings, platforms, research vessels, and even by ships of opportunity and ferries as instrument carriers. In addition, it is possible to observe objects with remote sensing techniques. With remote sensing applications there is no direct contact between the sensors and the objects (or events) being observed. Remote sensing typically refers to satellite or airplane-mounted sensors, however sometimes remote sensing sensors are mounted on a fixed platform. Different kind of observation techniques can be used to sense the earth or the atmosphere from a distance.
After an object has been observed, in-situ or with remote sensing techniques, the data need to be processed further. Data need to be collected, validated and archived in databases (data handling). Furthermore data needs to be converted to information. For the analysis, interpretation, and presentation of observational data it can be useful to construct models, and information systems to complement the observations. National and European legislative regulations such as the Water Framework Directive (WFD) and its implementation give a strong impetus to the development of new types of sensors and measuring strategies.
Methodology and Techniques
Sensor systems for a wide range of applications have been described. Instruments and sensors to measure environmental parameters are commonly used in oceanography, e.g. for parameters like temperature and salinity. The methodology comprises optical (including photo and video), acoustic, and radar techniques. Very specific types of sensors are used in studies of the behaviour, and the temporal and spatial distribution of marine and coastal organisms. Thus, application of data loggers to seabirds, for example, allows to study their distribution patterns or their foraging trips, and even their diving depth. However, the main portion of sensors is used in observational networks such as European coastal and marine observatories (2020)|coastal observatories, with both ships as well as stationary platforms like buoys to deploy instruments. This mainly monitoring-related research field will be extended in the future through the development of new and reliable sensors for specific chemical compounds (e.g. nutrients, dissolved gases).
Coastal observatories like stationary platforms are increasingly used for long-term observations. Although they only represent a single point in space they have no large restrictions regarding power supply and space. Moreover, in general it is easy to make vertical observations as well. The disadvantage of having a single point can be solved by using a few platforms as well as surveys to describe gradients between different stations, and remote sensing efforts (modelling exercises should help to define the cost-benefit of more or less stations within in specific sea area, depending on the spatial resolution needed).
Although biofouling can be relatively easy prevented in flow through systems, it still poses a problem for moored sensors in surface waters, especially in tropical and temperate waters.
A few successful applications of sensor systems are still missing, but should be added in due time. So far, no systematic contribution on the use and construction of platforms is available.
Furthermore, the application of Autonomous Underwater Vehicles (AUVs), as well as new developments in the field of bionics should be included by future articles, with emphasis on special requirements for operation in shallow coastal waters.
Although remote sensing is an important technique for observations on a large spatial scale, two contributions are yet available on the principles of passive optical remote sensing where we expect contributions for suspended matter, chlorophyll, and coastal habitats. The other contribution shows the results of a Dutch initiative for real-time algae monitoring. This is developed as part of a GMES – MARCOAST service. More applications of remote sensing are needed to show its applicability in coastal studies.
Currently, sensor systems and techniques in the field of global positioning and navigation are completely missing in the Coastal Wiki and need to be included.
Observational techniques in different disciplines
The number of observational techniques available for hydrographical measurements is rather large. This field is well documented in the Coastal Wiki and covers measurements of currents and turbulence by acoustic methods, waves and currents by X-band radar, and the Use of ground based radar in hydrography, methods to measure Light fields and optics in coastal waters, where attenuation is dependant on a series of factors, like suspended sediments, phytoplankton concentration and dissolved organic material. It is concluded with two extensive contributions on available measuring instruments for fluid velocity, pressure and wave height and on instruments for bed level detection. Methods described are those nowadays in common use such as ADCP, ADVs etc. The principles of the measurements are presented and applications are shown. Apart from the contribution in the main text of the Coastal Wiki substantial amounts of information are made available as background documentation (a complete manual).
The field of sediment transport is represented by a manual with 10 chapters on different aspects within this important coastal subject, i.e. the Manual Sediment Transport Measurements in Rivers, Estuaries and Coastal Seas. They range from definitions, processes and models to measuring instruments as well as laboratory and in situ analyses of samples. The individual chapters are very nicely documented with examples of observations. The large amount of information presented shows the importance of sediment transport in coastal areas. The complete character of this manual should be stressed. Access is given to several papers on selected issues.
The topic of coastal meteorology is included in the Coastal Wiki, providing mainly an overview of the theoretical background. The section on observational techniques in this field needs extension.
Applications of new techniques to observe biological and ecological parameters and processes is a wide field. The present number of articles and coverage of topics in the Coastal Wiki can be by far extended. The currently available articles are related to monitoring and mapping activities (see next section).
Monitoring and mapping techniques
Examples of specific activities in the monitoring of organisms are presented by the articles on Application of data loggers to seabirds, and on acoustic monitoring of marine mammals. The articles on real-time algae monitoring and on oil spill monitoring by satellites add to environmental monitoring activities. This is a field to definitely invite more authors to contribute to. Furthermore, the implications of political directives (national and EU), and the aspect of joint efforts among different EU nations need to be included.
From the technical perspective, the mapping activities described in the Coastal Wiki cover mainly optical techniques. They are represented by underwater video to observe both sediments as well as organisms in the water, by the land-based ARGUS video monitoring system that allows to follow (i) the effects of a storm event on the beach formation and structure, (ii) the temporal evolution of beach nourishment, (iii) the bathymetry of the surf zone, and the wave run-up on coastal structures, and (iv) the assimilation of model computations and video observations, and by the use of aerial photographs for shoreline position and mapping applications as substantial means to observe the position and structure of the coast and its dynamics over longer periods (up to several decades). Future developments might go into the direction of using satellite images for the same purpose, with the advantage of large-scale coverage. Likewise, mapping activities by remote sensing are dominated by optical techniques such as HyMap: Hyperspectral seafloor mapping and direct bathymetry calculation in littoral zones that allows bathymetric mapping and the classification of under-water vegetation, and the use of Lidar for coastal habitat mapping to measure altimetry or bathymetry by a laser technique which still is problematic in turbid coastal waters.
The topic of mapping-related methods is a wide field, where more authors should be invited. Besides the existing article on the Use of X-band and HF radar in marine hydrography, also acoustic in-situ methods such as sonars and multi-beam echo sounder, and remote sensing techniques such as satellite radar altimetry, and Interferometric Synthetic Aperture Radar (InSAR) need to be included.
Field observations in combination with model applications
So far, one contribution is available on the combination of remote sensing with other observational techniques (e.g. FerryBox) and water transport modelling, Coupled hydrodynamic - water quality - ecological modelling.
The existing model contribution is about data model integration as well as the importance of data assimilation into models. The article on Reduction of uncertainties through Data Model Integration (DMI) describes several important aspects of modelling such as dealing with uncertainties, stochastic models, calibration of models and sequential data assimilation into dynamic models. A concrete application of data assimilation into a model would be very useful for future users of these techniques.
Data bases and information management
A few contributions have been written on the important issue of data bases and information management. A good example is the contribution on NOKIS - Information Infrastructure for the North and Baltic Sea, which presents an information infrastructure for the North and Baltic Sea. It also contains several services for specific applications. Linked to this NOKIS contribution is another one on a gazetteer, a geographical dictionary, which will be used in the framework of the EU-WFD. Another data base described in the Coastal Wiki is the coastDat database at the GKSS Research Centre in Germany containing a compilation of coastal analyses (hindcasts) and future scenarios for the North Sea and NE Atlantic resulting from numerical models. A very new and promising approach of spatial data information management for applications in spatial planning and related fields is the development of a gazetteer which was developed for the German Bight together with the NOKIS data base. Missing are reviews of comparable systems in other countries.
Political aspects
Currently, there is only one article dealing directly with political aspects on Monitoring tasks and WFD for coastal waters in Greece. Other contributions are related only indirectly to EU directives or to monitoring tasks. There is an urgent need to complement the Coastal Wiki with this information, also covering particularly different European states. The conventions of OSPAR and HELCOM will be covered by an article in due time.
Conclusions
The coverage of theme 9 is rather extensive; the most important disciplines are physics, chemistry, biology, meteorology, oceanography. Most methods are derived from oceanography and from coastal morphology. A very large amount of information is already available, generally of high quality and good readability. Several examples from practitioners are included in the current contributions. However, at the same time there is a need to complete several parts, especially where important information is missing.
A better coverage of policy implications, and a better geographical coverage are needed. Tools would e.g. a short description of important models in use for water transport, sediment dynamics and ecosystems. Further contributions on other than optical remote sensing techniques would be welcome. Generally, the monitoring issue is well covered regarding the availability of different sensors, but rules and tools as well as guidelines for setting up a monitoring network for a specific question is not available yet. Remote sensing is not covered well enough to show the strength of its application.
The field of data bases and information management needs further improvements. In addition, examples from other countries should be included.
Generally, the coverage of items is typically northern European, and should be more extending towards the Mediterranean as well as to the Baltic Sea. Theme 9 has not yet reached a good national spread over Europe which should be improved in the near future with the help of the ENCORA network.
Promising techniques for monitoring sustainability are combinations of different techniques e.g. in situ observations, with remote sensing and modelling as a combined tool for water quality problems (WFD). Furthermore, the development of new data assimilation techniques is promising, but still no good examples or incorporation of these techniques in ecological ecosystem models exist.
Sustainable development - operational definitions, practices in EU countries, impact of measures and guidelines for policy/practice is an issue that can be dealt with only through the comparison between the results of the different Themes. For Theme 9 alone this question can not be answered with any reliability.
Coastal Wiki articles on Field Observation Techniques are listed in the category:Coastal and marine observation and monitoring
Please note that others may also have edited the contents of this article.
|
