Wan Naim Wan Mohd

Air quality monitoring using remote sensing and GIS technologies

Air quality monitoring is needed to control air pollution in urban areas. A limited number of air quality monitoring stations limits the initial strategy of pollution prevention program in Malaysia especially at micro-scale level. Existing technique used to monitor air quality involves manually measured pollution concentrations within the area of measuring station. New technique which integrates satellite remote sensing and Geographical Information System (GIS) by the authors can be used to continually monitor air quality at micro-scale level. Images from Landsat 7 Enhanced Thematic Mapper Plus (ETM+) and eight (8) Continuous Air Quality Monitoring Stations (CAQM) data are used to determine the relationship between digital number (DN) of the thermal infrared band and the two (2) air pollutant parameters, i.e. Carbon Monoxide (CO) and Particulate Maters (particle less than 10 microns in size - PM10). A number of models have been developed by the authors to relate the DN of Landsat 7 ETM+ and the air pollutant parameters. Since there are limited numbers of CAQM stations available, the concept of “virtual stations” is introduced to densify CAQM stations. Based on these stations, kriging interpolation method (available in GIS software) is used to generate the air quality maps of the study area. The advantage of this method is it allows a more detailed assessment of air quality within urban areas with limited CAQM stations. Maps of pollution concentration generated from virtual stations using kriging interpolation method produce a more realistic distribution of air pollution. The concentration of CO and PM10 are highest in the industrial zones of the study area (Shah Alam). This method can be used by environmental managers and local authorities to continually monitor air quality in urban areas.

A generic approach for photogrammetric survey using a six-rotor unmanned aerial vehicle

This paper discusses a rapid production of slope mapping using multi-rotor unmanned aerial vehicle (UAV). The objective of this study is to determine the accuracy of the photogrammetric results based on novel method of multi-rotor UAV images as well as to analyze the slope error distribution that are obtained from the UAV images. This study only concentrates on multi-rotor UAV which also known as Hexacopter. An operator can control the speed of multi-rotor UAV during flight mission. Several ground control points and checkpoints were established using Real Time Kinematic Global Positioning System (RTK- GPS) at the slope area. Ground control points were used in exterior orientation during image processing in sequence to transform image coordinates into local coordinate system. Checkpoints were established at the slope area for accuracy assessment. A digital camera, Sony NEX-5N was used for image acquisition of slope area from UAV platforms. The digital camera was mounted vertically at the bottom of UAV and captured the images at an altitude. All acquired images went through photogrammetric processing including interior orientation, exterior orientation and bundle adjustment using photogrammetric software. Photogrammetric results such as digital elevation model, and digital orthophoto including slope map were assessed. UAV is able to acquire data within short period of time with low budget compared to the previous methods such as satellite images and airborne laser scanner. Analysis on slope analysis and error distribution analysis are discussed in this paper to determine the quality of slope map in the area of interest. In summary, multi-rotor UAV is suited in slope mapping studies.

Functional relation of land surface albedo with climatological variables: a review on remote sensing techniques and recent research developments

Surface albedo has been documented as one of the Essential Climate Variables (ECV) of the Global Climate Observing System (GCOS) that governs the Earths Radiation Budget. The availability of surface albedo data is necessary for a comprehensive environmental modelling study. Thus, both temporal and spatial scale issues need to be rectified. This study reports about the availability of surface albedo data through in-situ and remote sensing satellite observations. In this paper, we reviewed the existing models for surface albedo derivation and various initiatives taken by related environmental agencies in order to understand the issues of climate with respect to surface albedo. This investigation evaluated the major activities on albedo-related research specifically for the retrieval methods used to derive the albedo values. Two main existing albedo measurement methods are derived through in-situ measurement and remotely sensed observations. In-situ measurement supported with number of instruments and techniques such aspyrheliometers, pyranometers and Baseline Surface Radiation Network (BSRN) and remotely sensed observations using angularly integrated Bi-directional Reflectance Distribution Function (BRDF) by both geostationary and polar orbit satellites. The investigation results reveals that the temporal and spatial scaling is the major issues when the albedo values are needed for microclimatic study, i.e. high-resolution time-series analyses and at heterogeneity and impervious surface. Thus, an improved technique of albedo retrieval at better spatial and temporal scale is required to fulfil the need for such kind of studies. Amongst many others, there are two downscaling methods that have been identified to be used in resolving the spatial scaling biased issues: Smoothing Filter-based Intensity Modulation (SFIM) and Pixel Block Intensity Modulation (PBIM). The temporal issues can be resolved using the multiple regression techniques of land surface temperature, selected air quality parameters, aerosol and daily skylight.

Air quality parameters dependency of remotely-sensed albedo

Land surface albedo has large daily and seasonal variation in many regions. Malaysia, for being located at the tropical region, experiencing constant illumination of sun and receiving two monsoon seasons namely northeast and southwest and two inter-monsoon seasons in Mar-May and during Oct-Nov, the diurnal variation of heat may somewhat be different. This study attempts to investigate the relationship between land surface albedo (LSA) derived from the MODIS with the selected air quality parameters. The objectives includes to determine significance relationship between LSA with ambient temperature and to identify the significance factor of other identified variables such as UVB, windspeed, Humidity and CO2. Using linear trend correlation analyses technique based on Pearson correlation coefficient, the strength and direction of the relationships between MODIS spectrally derived LSA are identified along with the relationship between selected dependent and independent variables were visually inspected.

Evaluation of Vertical Accuracy of Airborne IFSAR and Open-Source Digital Elevation Models (DEMs) for Flood Inundation Mapping

Acquiring an accurate elevation model for flood inundation mapping is essential and can be considered as an expensive task. One possible solution is to acquire readily available digital elevation model (DEM) or open-source DEMs such as ASTER GDEM and SRTM. The issue is how accurate are these datasets and can it be used for flood inundation mapping. The objective of this paper is to evaluate the vertical accuracy of DEMs acquired from different data sources. Results presented in this paper are part of an undergoing research to evaluate the use of global DEMs for flood inundation mapping. For the evaluation of vertical accuracy, DEMs acquired from Airborne IFSAR, ASTER and SRTM Void Fill are used to generate height points. The results obtained are compared with height from GPS observation of two different test sites located in Alor Setar and Kuala Nerang, Kedah. The terrain characteristics of Alor Setar and Kuala Nerang test sites are flat and variable terrain respectively. The overall vertical accuracies of IFSAR DTM, IFSAR DSM, ASTER, and SRTM Void Fill for Alor Setar are ±0.497, ±1.529, ±5.848, and ±4.268 m, respectively. For the undulating terrain, the vertical accuracies of these DEMs are slightly lower, i.e., ±0.841, ±2.092 and ±5.300 m. The height accuracy of ASTER GDEM in undulating area is found to be higher than relatively flat area, i.e., ±3.278 m. Findings from this preliminary test have shown that the vertical accuracy of airborne IFSAR DTM is quite high and can potentially be used in flood management.

The Improved Conceptual Design of Web-based GIS Residential Property Marketing Information System

This chapter attempts to show the conceptual design a Web-based GIS Residential Property Marketing Information System (WGRPMIS). This system is intended to be integrated with the virtual GIS technology enabling the consumer to virtually explore the potential property based upon the multi criteria selection through assisted geo-processing query. The proposed system is built using Adobe Flex on ArcGIS Server framework to enable geo-processing and geometric network capabilities. Through the pilot system, the success of 3D and virtual reality integration was revealed. Due to limitations of the query functions and 3D feature complexity taking its toll on the system’s performance, an improved geo-processing scheme is presented in this paper and the conceptual design of this system is revised. The improved query function which includes road network and accessibility were taken into consideration in solving buffer and radius query is developed. The revised conceptual design will further be used in designing the simplified 3D visualization viewer to the Virtual panoramic display.

The Effects of Vegetation Growth on the Microclimate of Urban Area: A Case Study of Petaling District

It is well known that the surface temperature distribution in the urban area is significantly warmer than its surrounding suburban areas. This phenomenon is known as urban heat island (UHI). Vegetations play a vital role to mitigate the UHI effects especially in regulating high temperature in saturated urban area. This study attempts to assess the effect of vegetation growth on the surface temperature distribution of the surrounding areas. The area of study for this research is Petaling District (i.e. City of Shah Alam, Petaling Jaya and Subang Jaya), Selangor. To monitor the land use/land cover changes within the study areas, Landsat 5 TM images of 1991 and 2009 are used. The land use/land cover of the study area is classified into five major classes i.e. water bodies, high-dense trees, mix-vegetation, built-up area and open land. Based on the thermal band of Landsat 5 TM, the land surface temperature maps are derived. Mono-window algorithm is used to convert digital number to surface temperature. Results from this study have shown that there are significant land use changes within the study area. This study demonstrates that rapid urban growth significantly decreased the vegetated area, hence increased the surface radiant temperature. Although the conversion of green areas to residential and commercial areas significantly increases the land surface temperature (LST), matured trees help to mitigate the effects of UHI.

Diurnal microclimate variations in tropical rainforest: Case study of Kuala Tahan, Pahang

Forest plays an important role in maintaining the environmental quality and the ecological balance of their surrounding areas. Therefore, understanding the effects of tropical rainforest destruction and fragmentation on the microclimate is critically needed. National Park, Pahang is one of the oldest tropical rainforest where the surrounding areas are facing critical threats due to tourism activities and infrastructure development. Solar radiation (I), air temperature (Ta), relative humidity (h), wind speed (v) and rainfall were measured at six different locations under the forest canopy, built-up area, trail, campsite, fragmented forest and village area. All the microclimate variables show significant differences at the measured locations. These results further the understanding of the responses to forest fragmentation in the tropical forests created by human activities, and provide a useful basis for evaluating the implications of forest management practices.