EDASnet

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EDASnet

Networked Data Collection 

EDASnet - The Design Model

EDASnet - Database Structure

The concept behind EDASnet is to provide Environmental Data collection systems using distributed computer processing and saving the results in a standard database format thus making use of modern computer networking technology.

The following diagram describes a typical environmental data collection system with two Tide Gauges and a Weather Station directly connected to a single PC, the outlying '+' characters indicate the logical point to expand the systems, in this case by making more connections directly to the PC ...

Single PC systems tend to be legacy designs that have evolved around existing equipment, probably having been added to at various times in their history and almost certainly the result of ad hoc software updates and changes. The basic concept of a single PC acting as a central data collection and display point has proved to be a very cost effective solution to the problem of collecting and recording environmental data. These systems without doubt have proved their reliability in collecting and storing environmental data, however as computer and information technologies progress these systems are starting to show their limitations. With testimony from many users the general problems areas with these single PC systems are as follows ...

bulletComplex software trying to manage all tasks from one thread.
bulletDifficulty in adding more Gauges/Stations to the existing system.
bulletProblems with replacing non-standard serial and A2D cards in PCs.
bulletLimited ability to connect more than two serial port devices.
bulletProblems with running cables through buildings to one computer.
bulletNon-compliance with Year 2000 transition in Software and Hardware.
bulletTimekeeping problems with PC clocks and hardware changes.
bulletDifficulty in updating software to modern graphic operating systems.
bulletProblems with access, backup and presentation of data collected.
bulletData not readily available to wide range of potential users.

The following diagram outlines the logical design of a system that performs the same task as the previous single PC system but is designed around networking principals. As with the previous diagram the '+' characters indicate the points at which the system can be expanded ....

From the above diagram it can be seen that the system can be expanded almost indefinitely by either making connections to existing PCs or by adding PCs to the network. The single PC system can actually be simulated using the network model with all programs (Clients) running on one machine and the interconnecting network being the internal data bus. In most applications the network would consist of a number of interconnected computers using a standard cabling and protocol scheme supported by the operating system. The location and use of each machine would be determined by normal constraints such as nearness to peripheral devices (in this case Tide Gauges and Weather Stations) or by the power of the machine (e.g. fast machine with large hard disk would be the data storage and server node). Output nodes would be computers on the desks of users wishing to see or have access to the data. Input nodes would be computers running Input Client programs and connected to the environmental devices either directly by cable or indirectly by telemetry.

EDASnet - The Design Model

EDASnet - Networked Data Collection

EDASnet - Database Structure

The major difference between the design of 'single PC' and the 'Network' Environmental Data collection model is that the network model has been broken into logical 'components'.

Each component executes as a single task which under modern operating systems can be run concurrently on the same or different computers across a network. The main components identified in a Networked EDAS system are as follows ....

Input Clients These are programs run on machines directly connected to the input devices (instruments) such as Tide Gauges and Weather Stations. These programs capture , filter and pre-process (e.g. average) the data generated by the connected device. There are several of these programs, each supporting different formats and peculiarities of a particular manufacturer's instrument. They all collect the data save it in a standard database format/table using the database drivers. Local display is used to present data received, detected errors in equipment and system errors such as Server not responding.
Data Server This is a client interface program normally referred to as ODBC32 and is supplied as part of, or as an add-on to the underlying operating system. The two driver variants currently in use by Lymtech with this server are the Access and/or the SQL server database drivers provided by Microsoft. Local display of information is provided by the database product or by using operating system utilities supplied with the server software.
Output Client This is a client program which collects its data from the database via the Data Server and provides a screen presentation of the data at the users location. Typically this would be a series of graphs and numeric windows showing both collected data and derived data such as average Wind Direction over the last 10 minutes. These clients can easily be authored by a software writer as the data provided is in a standard format and conforms to the WOSA standard as outlined in the ODBC documentation.
Passive Client These are programs that can be run anywhere on a network and listen for a particular message to be transmitted. The message is captured and displayed, the only user settings being the choice of message and local display settings. The programs are entirely passive and are not able to change or access the 'live' data in any way.

Each of the above software components can be tailored to run across a network of computers and provide a 'scaleable' system. By having a distributed system there are several features which add robustness to the data collection system ..

bulletEach node can be designed to fail without causing system failure.
bulletNodes can be easily replaced, moved, increased or substituted.
bulletData can be collected over wide area networks.
bulletData can be accessed over wide area networks.
bulletData can be accessed by common office software products.

EDASnet - Database Structure

EDASnet - Networked Data Collection

EDASnet - The Design Model

Data collected using the EDASnet system is saved in a standard, commercially available database format. Currently this format uses products which are designed using the Microsoft JET database engine technology such as Access and SQL server.

The database is a common holding area for a variety of data sets that can loosely be described as 'Environmental'. Each parameter has two relational Tables associated with the data being collected ...

Data Table Actual data collected for each instrument of this table's type and stored in time series order

 

Info Table Relational information about each instrument in the set.

To date there are two major areas of data which have been addressed by Lymtech and are included within the database design ...

Tide Gauge Data This includes recorded and predicted values of tidal elevation at given location coordinates and includes allowance for basic wave statistics such as Maximum, Minimum and SD.

 

Weather Data These parameters include Wind (Speed, Direction and Gust), Barometric Pressure, Air Temperature, Rainfall, Solarimeter and Relative Humidity.

Using a database is not the most efficient way of storing environmental data but it is the best compromise of storing the information in a structured form and retrieving it a a later date. With the low cost of modern data storage, the benefits of being able to retrieve data using database tools such as Selection and Sorting, then being able to process the data in commercially available products such as Spreadsheets greatly outweigh the initial costs of hardware.

      

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  Copyrightę2011 Lymtech LLC - Last modified: 02-07-2011