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ArcView basics

INSROP GIS is a customised GIS application based on ArcView® 3.x software. ArcView works with views, tables, charts, layouts, and scripts, stored in one file called a project. A project file stores information about the contents and status of each project component, including storage locations of the data sets used in the project. The actual data are not stored in the project file. Hence, if any data set is updated, the updates are also reflected in the ArcView project. However, this also means that data sets cannot be moved to another location without updating the project file. Project files are stored with an '.apr' extension.

A view is an interactive map that enables display, exploration, queries and analysis of geographic data. The view defines the geographic data and how to display them, but does not contain the actual data themselves; only references to these data. The spatial part of a database stores information about where the data are located, while the tabular part of the database provides descriptive information about the elements contained in the database. This information can be used to choose how (colour, symbol, text etc.) the data are to be displayed. The data sets to be included in a view are included as themes, and must be prepared in ARC/INFO format, as a raster image, or created as ArcView shapefiles from X-Y co-ordinates. Each theme can be thought of as a geographic information layer. The options for manipulating images are limited, and images are primarily intended for use as background (unless you have an ArcView Extension).

Tables and charts work in a fairly similar manner as a simple spreadsheet in the sense that the tables include data records with several columns, and that charts can be created from the values in data columns. Data values in a column can also be calculated from values in other columns. However, pure spreadsheet tasks are better performed in state-of-the-art spreadsheets. The strength of the ArcView tables and charts is the connection to the geographic data in the view. Spatial data sources such as ARC/INFO coverages have attribute tables comprising descriptive information about the geographic features they contain. Any selection of spatial features in a view also means that the tabular records of these spatial features are selected. Any statistical analysis of data columns in the attribute table or displayed charts will now only include the values from the selected features. This is particularly useful to analyse features satisfying certain spatial criteria, e.g. being within a limited area or within a limited distance from another feature, e.g. a ship track. Also, any selections made in an attribute table mean that the corresponding spatial features are selected. This is particularly useful for seeing where features satisfying certain descriptive criteria are located. In addition to the attribute tables, other tables (in dBase, INFO, or delimited ASCII format) can be joined (one-to-one relation) or linked (one-to-many relation) to an attribute table, provided they both include a suitable data column. Linked tables can be linked to other tables and thereby enabling many-to-many relations.

A layout is the framework for preparing graphical output, such as maps, charts, and table records, for hardcopy printing or to be saved on files for import into word processors or publishing applications. The elements of a layout can be dynamically linked to the view, table and/or chart windows, so changes in any of these windows are reflected in the layout. In addition the layout may include various graphical elements such as graphical files, text, frames, north arrow, scale bar and legend box. The scale bar and legend box are as default linked to the view to reflect map scale and legends of the selected themes in the view. The layout may also include several views, charts etc.

A script is the component of an ArcView project that contains AVENUE code. AVENUE is an object-oriented programming language, from which ArcView is developed, and AVENUE can be used to customise ArcView or to program special analysis tasks not available from the default ArcView interface. INSROP GIS is developed using AVENUE scripts, but AVENUE is not required to use INSROP GIS.

The ArcView components are run in separate windows. The ArcView window is the main window and serves as the background for all other ArcView operations. The project window allows management of the individual components of the project.

The project files also include information on the display status, screen location, size etc. of the various component windows. The ArcView user's interface also includes menu, button and tool bars at the top of the ArcView window. These vary for each ArcView component, and the menu, button and tool bars shown in the ArcView window are always the ones for the active window. The ArcView window also includes a status bar at the bottom of the window. The ArcView interface is stored in the file 'default.apr' in the 'etc' sub-directory below the ArcView installation folder.