Development of multiple query web GIS for growing databases : a case study of land and water information management

Abstract

Land and water information systems are developed for managing the information such as location, its limit , characteristic, structure, ownership if available and other relative attributes. For presenting the geographical locations of the land and water features, map based systems are being developed. Present day Geographic Information Systems (GIS) are map based systems which enable the interaction of several map layers for desired output. Most of the available WebGIS applications for land and water information are limited to selected features, such as roads, rivers, buildings and forest features. Some are limited to defined Geographical area, while only primary attribute values are displayed by some other applications. However, with the increment of requirements for WebGIS application, information and functions are being enhanced rapidly. When serving large data through a WebGIS application, performance tend to be slowed. Therefore it is important to identify the issues of WebGIS application in case of growing databases. Overall objective of the study is to identify the issues and concerns related to the development of Web GIS applications for growing databases and then to develop a land and water information system in order to identify management issues pertaining to the tool development associated with map serving and combined querying. The specific objectives of the research are: Identification of WebGIS performance issues with respect to the spatial coverage expansion and attribute expansion and development of a land and water management WebGIS tool with user friendly search capability considering possible expansion of coverage. As very first step, the issues of available web GIS applications are identified by a literature survey. Meanwhile, a evaluation on development methodology, performance optimization techniques and performance calculation methods is carried out. The work commenced with the development ofWebGIS application including information and functionality at basic level. According to the user survey, the application was enhanced for another three stages with growth of database and functional operations. The growth rate of database size second stage of the application is twice than first stage. While third stage growth rate is five times than second stage and fourth stage having about fifteen times of growth rate of features. The testing process of each stage was carried out to identify user familiarity, accuracy and performance level of the application. Performance level was identified by calculating the response time of functions at each stage. GeoInfo WebGIS application with better efficiency level of functionalities, user friendly features and high accuracy level is one of major results of this research. Functionalities ofWebGIS application are listed as (i) Query for land and water features, their attributes and relative features. (ii) Map the geographically location of water and land features and (iii) GIS operations such as location identification, measure length/area, map zoom in/out, pan map and vector and raster data layers loading. JavaScript, XML, HTML, and PHP are programming languages for the development of the application, while Postgis is selected as the database.Database to database functions take high response time of 22.5 seconds in Version 4 while map to database ii having the 3.42 seconds as minimum compared with first level ofWebGIS function categories. When considering all the functions are considered, ”Measure Tool Operation” has the minimum response time of 0.42 seconds and Maximum is the 59.2 seconds and it is the response time of ”Displaying list of Buildings” function. A rapid increment of response time is with functions of fourth versions. Other identified issues are non responsive situations with loading images, take more time to data loading and map overlaying when browsing and changing . By evaluating results of the verification process it is identified that database transactions directly affect the efficiency of functions ofWebGIS application. Reasons for Identified issues of WebGIS land and water management are (1). Issues with performance of stored procedure (2). No factor query index (3). Low efficient configuration of server (4).Issues with cache memory and (5). Trying to load heavy maps and data Recommendations for WebGIS development are (1).Database to database functions should be minimize as possible for the best performance of Water and land information management WebGIS application. (2). When serving the Raster and Polygon data, size should be in small components as possible. (3).Careful action should be taken when loading more than 10 or 20 records at a given time