Design and implementation of a web-based GIS for the Iranian Roads Information

Need analysis and Methodology
The object of the TTO project is to disseminate Iranian road Information through the Internet so that constituent can easily access the data. The requirement analysis step has been performed through interviewing potential users. This steps produced two critical pieces of information:

A list of functions that is needed. The required functions are the basic visualization function such as Pan, Zoom, and more advanced function such as object identification, attribute query, shortest path, location map, clear selection, moving the view, download and measuring. Client can use these functions to view road information, and peripheral constructs such as gas station and rest area.
A master list of available/needed geographic data. TTO has captured several layers of road information using GPS. In this project, Only 25 layers of Information have been used that includes police station, restaurants, gas station, mosque, etc.

Once the required data has been identified, the data model that identifies the entities and their relationship were designed. Since, the data will be delivered through a central server and clients will access to raster formats, client side strategy was chosen providing the users access to interactive map.

Selecting suitable software is an important step in a successful implementation. Software was evaluated on functionality and performance, and independent of the hardware and operating system. Web GIS requires specific hardware configuration. Since the volume of transferred data is huge, the speed of Internet connection is vitally important. Most of the data are sent from map server to clients, as such the Send speed has been identified to be more than 128kbs. Based on a pilot project and the experienced gained through similar projects, a Dual Processor computer with 512 MB Ram has been selected for this project.

The initial Requirement Analysis contained some applications of a complex nature. However, the majority of initial applications was straightforward, and can be implemented using the basic functionality that is part of the Web GIS software (e.g., display). The more complex applications were not supported by the basic functions of Web GIS but have been programmed. Ease of use, user-friendliness, and reducing the volume of data transfer were the critical issues considered in the development. http://www.iranroads.com shows the user interface that has been programmed using HTML, Visual Basic and Java Script.

Before it can be implemented the strategy it must be first understand how web pages work.

Data entering via web page
Web pages are based on special language known as Hypertext Transfer Language or HTML.HTML is a language that web browsers such as Internet explorer can understand. It’s fairly easy language to understand although advance web pages can be quite complex.

In this section, input devices for client such as checkbox, selection list, radio bottom, text box, image bottom, submit bottom and hidden inputs are explored.

Checkbox: It is used for selecting the available layer of data in the map for making them visible or invisible on the map.
Radio bottom: Commonly the active layer of data in GIS is single. for activating the layers for running function like identify radio bottom is used.
Selection list: This input device used for building query from existing items in database. Also in shortest path function the selection of start and destination cities is done via selection list.
Image and submit bottom: Image and submit bottoms is the most useful input device in user interface web GIS site. For running all of the functions this input device is used.
Textbox: It’s used only for entering the downloading process password.
Hidden Inputs: This inputting method that is input the user does not see, but server will see. For example in order to pass a hidden input (map extent) based on user input from previous page require that second page be constructed after the user has selected the variable to be passed.

Each input is sent to the server paired with its value. In addition of using HTML primary input object, Java script technology is used for managing these object property and events. For example by using this technology the legend opening and closing is managed.

Figure 1: Web-GIS User Interface