The 3rd ISPRS Workshop on Dynamic and Multi-Dimensional GIS & the 10th Annual Conference of CPGIS on Geoinformatics

Chen, Jun

Bibliographic data

Monograph

Persistent identifier:: 856566209

Author:: Chen, Jun

Title:: The 3rd ISPRS Workshop on Dynamic and Multi-Dimensional GIS & the 10th Annual Conference of CPGIS on Geoinformatics

Sub title:: May 23 - 25, 2001, Bangkok, Thailand

Scope:: VI, 434 Seiten

Year of publication:: 2001

Place of publication:: Pathumthani, Thailand

Publisher of the original:: AIT

Identifier (digital):: 856566209

Illustration:: Illustrationen, Diagramme, Karten

Language:: English

Usage licence:: Attribution 4.0 International (CC BY 4.0)

Publisher of the digital copy:: Technische Informationsbibliothek Hannover

Place of publication of the digital copy:: Hannover

Year of publication of the original:: 2016

Document type:: Monograph

Collection:: Earth sciences

Chapter

Title:: GIS-BASED SYSTEM FOR RAINFALL ESTIMATION USING RAINGAUGE DATA: A PROTOTYPE. Yinchai WANG, Teck Kiong SIEW

Document type:: Monograph

Structure type:: Chapter

ISPRS, Vol.34, Part 2W2, “Dynamic and Multi-Dimensional GIS”, Bangkok, May 23-25, 2001 310 GIS-BASED SYSTEM FOR RAINFALL ESTIMATION USING RAINGAUGE DATA: A PROTOTYPE Yinchai WANG Faculty of Information Technology, Universiti Malaysia Sarawak, 94300 Kota Samarahan, Sarawak, MALAYSIA Tel:+60-82-671000 ex377, Fax:+60-82-672301, E-mail:ycwang@fit.unimas.my Teck Kiong SIEW Faculty of Information Technology, Universiti Malaysia Sarawak, 94300 Kota Samarahan, Sarawak, MALAYSIA ABSTRACT High-quality rainfall measurements on a variety of temporal and spatial scales are desirable for a wide range of applications. Reliable values of rainfall are not yet available for most areas over Sarawak because of scarcity of gauge measurements. This research developed the optimal rainfall estimation model to estimate monthly rainfall from the surrounding rainfall stations. The technique pursued was a geostatistical approach by taking into account the effect of topography factor on spatial variation of rainfall. But, there are problems with the topography factor especially in dealing with geographical data and spatial analysis. These problems, that can not be solved manually, were overcome with the aid of GIS which has full capabilities in generating geographical data and performing spatial analysis. Thus, the whole system was implemented using GIS. The procedure involved was the interpolation method applied over the determined best area of interpolation in which all the surrounding rainfall stations were significantly correlated to the point which rainfall was to be estimated. Regression analysis was applied for model selection. The optimal rainfall estimation model selected was the best multiple linear regression equation that consists of topography parameters as independent variables, applied over the best area of interpolation. Cross-validation was used for the optimal model evaluation and for comparing with six alternate estimation methods. The optimal model provided the best cross-validation result. The output was a GIS based Rainfall Estimation System for estimating point and are-average monthly rainfall at an unmonitored site, and for distributing point rainfall estimates to regular spaced grid cells in producing isohyets of monthly rainfall over the study area. 1. INTRODUCTION In Sawarak, many human and economic activities involving agriculture, industry, commerce and transportation are extremely reliant on the weather conditions. Observation of rainfall includes raingauge measurement that is the direct and quantitative measurement of rainfall, provided by all the rainfall stations. Space observation of rainfall refers to infrared (IR) satellite and radar data that give an indirect measurement of rainfall in terms of temperature and reflectivity, provided by satellite and radar at Kuching Meteorological Station only. Quantitative measurement of rainfall are preferred and required by many activities and models. The main problem with raingauge observations lies in the lack of dense network. As compared to vast landmass and complex terrain, there is a lack of conventional gauge measurements in Sarawak, which prevents adequate sampling of rainfall observations for many applications such as agriculture and hydrological models. In view of this scarcity of observation, estimates of the amount and spatial distribution of rainfall are critical inputs to a variety of these models. However, obtaining reliable estimates is particularly difficult when the area coverage provided by the surrounding stations is sparse and when rainfall varies greatly with locations due to topographic effects which involve normal land or sea breeze effects and upslope or downslope motion of the monsoon flow over the mountains. In order to take into account these topographic effects, which involve spatial data, into rainfall estimation, there is a need of analytical tools dealing with spatial data and analysis, which can not be done manually, to improve rainfall estimation. This acts as a main hindrance in an effort to develop rainfall estimation model to estimate rainfall. Until recently, the advancement in computer technology especially the recent development of GIS provides tools tackling the spatial data. GIS, systems which deal with spatial information, map processing, spatial database and spatial analysis, can play an important role in dealing with organizing and integrating apparently disparate data sets together by geography and performing more complex spatial analysis. The main objective of this research is to estimate rainfall at unmonitored site using rainfall data from surrounding raingauge stations using the interpolation procedure with the integration of Geographic Information System (GIS). With the aid of GIS, topography factor itself, consists of other variables such as elevation, barriers and land-sea distribution, affecting the rainfall and its distribution greatly can be analyzed to study its extent of effects to rainfall estimation which, otherwise, is a very difficult task. Thus, GIS enables rainfall estimation technique to include as many parameters of the topography factor which involves spatial data. This study will focus on how to incorporate spatial analysis into the rainfall estimation and monitoring using raingauge data. The rest of this paper is organized as follows: Section 2 consists of literature review on the rainfall estimation techniques. Section 3 discusses the components of the methodology in deriving the optimal rainfall estimation model and developing GIS-based system. Section 4 describes the implementation of the whole system. Analysis and conclusion are given in sections 5 and 6 respectively. 2. LITERATURE REVIEW 2.1. Rainguage - Rainfall Estimation Raingauge networks measure rainfall accumulations on the ground at fixed locations. There is a tendency to underestimate rain amount due to physical and human errors such as wind direction, surrounding object, overflow and observation errors. Inspite of this, raingauges still give very good point accuracy. However, raingauges also suffer serve limitation in sampling especially over ocean and remote land areas as most of raingauges tend to be distributed with a pronounced spatial bias toward populated areas along the coast and against areas with high elevation and/or slope . In spite of this, several studies have demonstrated the utility of simple models based on the point data to diagnose factors such as topography, geology, hydrographic and vegetation which are observed to cause rainfall variations even over short distances such as a diagnostic model for estimating rainfall [1].

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