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Design of a geographic information supported database for the management of pressurised irrigation systems at the plantation du Haut Penja, Cameroon

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par Chick Herman AZAH
University of Dschang - Agric engineer 2009
  

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3.3 Development of the Database for the Irrigation System

The database was developed using Microsoft Access 2003 which is a relational database management system (RDBMS). The model thus developed under this software helped us to relate the various aspects of the system and led to the development of a conceptual and physical model of data. Figure 3.2 shows the architecture of the GIS database

The procedure for the development of the database within MS Access 2003 included:

· The review of existing data

· The identification of entities and their attributes

· The creation of tables, primary and foreign keys


· The definition of relationships

· Creation of data entry and retrieval forms

· Creation of queries

Irrigation Service

GIS DATABASE ON THE
IRRIGATION SYSTEM

Crop Water Needs Irrigation

Irrigation System

Scheduling Options

Figure 3.5: Architecture of the GIS database 3.3.1 Data review

Data was reviewed to identify entities, attributes and facilitate the classification and coding of data. At the start of the study, most of the data for the PHP irrigation system had been entered into MS excel 2003 spreadsheets. These excel spreadsheets were then transformed into MS access tables. This decision was made to avoid the re-entry of data as far as possible. The excel files where then exported to obtain MS access tables. However, the data on the final table required some cleaning. This was preferred to a re-entry of the data into MS access because of the time needed to re-enter data.

3.3.2 Entity and attribute identification

Entities were identified and attributes determined. The objective was to create normalized, non-redundant table structures. Several entities regarding to the irrigation system have been identified with respect to their function in the system. Thus, we started from the pumping station up to the crop in order to determine the various components which will constitute entities for the irrigation system database.

3.3.3 Table and key creation

On the basis of the entities determined tables were created. A primary key was established for each table. The primary keys were defined as Autonumber? field types to facilitate data entry and to avoid doubles in the data. Tables for the production plots, irrigation plots, climatic data, soil data, pumping stations, pipes, sprinklers etc have been created. Four principal methods exist in MS access for the creation of tables.

· Design Mode

This method was used most often as it enabled us to name tables and organize the structure of each table. This method has been used for tables which did not exist in other formats.

Field name

Primary key

Data type

Figure 3.6: Creation of table in design mode under MS access

· Table assistant mode

Here, access proposes different models of pre-established tables to choose from and create the desired table. The table was then personalized in order for it to suit the conditions required.


· Import table mode

This method has been used for the design of most of the tables that are being presented in this database. The rationale for this was the fact that most of the data concerning the irrigation system has already been stored either as texts or in MS excels spreadsheets. This made it easy for us to import the tables to our database and then define the contents of each field to suit the requirements of our database under the design mode by modifying the specifications of the various fields involved.


· Attach table mode

This method has been used for files that need to remain in their original database such as excel files on which calculations have been done. Hence the link between these files and the attached table in MS access remains and any modification on the file immediately leads to a modification in the attached table. In the calculation of the crop water requirements, the excel spreadsheet on which all the formulas were entered was exported to the database.

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