N. Mohd. Saleh

Aerosol Optical Thickness data retrieval over Penang Island, Malaysia

In this study, we propose a new cost effective approach to retrieve Aerosol Optical Thickness (AOT) data in the visible spectrum by using sky transmittance measurements measured by a handheld spectroradiometer. The transmittance values were measured in spectral region from 350 nm to 1050 nm at the earths surface. The well known Beer-Lambert law was used in this study to retrieve AOT values from the measured transmittance value. The concentrations of particulate matter of less than 2.5 micron (PM2.5) were measured simultaneously with the measurements of the transmittance data. The station locations of the PM2.5 measurements were detemined using a handheld GPS. Three interpolation techniques, namely Kriging Interpolation, Inverse Distance Interpolation and Natural Neighbour Interpolation, were used for mapping the PM2.5 concentration in this study. The accuracies of the three interpolation techniques were determined in this study in order to select the most suitable technique for mapping the air pollution concentration over Penang Island, Malaysia. The results of the analysis indicated that the AOT values were linearly correlated with the PM2.5 readings. AOT and PM10 maps were generated using an interpolation technique (Kriging) based on the measured data. Basically, both PM2.5 and AOT maps agree reasonably well over Penang Island, Malaysia. The highest PM2.5 concentrations were found in densely populated and industrialized areas.

Application of remote sensing in coastal change detection after the tsunami event in Indonesia

Shoreline mapping and shoreline change detection are critical in many coastal zone applications. This study focuses on applying remote sensing technology to identify and assess coastal changes in the Banda Aceh, Indonesia. Major changes to land cover were found along the coastal line. Using remote sensing data to detect coastal line change requires high spatial resolution data. In this study, two high spatial data with 30 meter resolution of Landsat TM images captured before and after the Tsunami event were acquired for this purpose. The two satellite images was overlain and compared with pre-Tsunami imagery and with after Tsunami. The two Landsat TM images also were used to generate land cover classification maps for the 24 December 2004 and 27 March 2005, before and after the Tsunami event respectively. The standard supervised classifier was performed to the satellite images such as the Maximum Likelihood, Minimum Distance-to-mean and Parallelepiped. High overall accuracy (>80%) and Kappa coefficient (>0.80) was achieved by the Maximum Likelihood classifier in this study. Estimation of the damage areas between the two dated was estimated from the different between the two classified land cover maps. Visible damage could be seen in either before and after image pair. The visible damage land areas were determined and draw out using the polygon tool included in the PCI Geomatica image processing software. The final set of polygons containing the major changes in the coastal line. An overview of the coastal line changes using Landsat TM images is also presented in this study. This study provided useful information that helps local decision makers make better plan and land management choices.

Determination of cloud and aerosol layers using CALIPSO and image processing

The height of cloud and aerosol layers in the atmosphere is believed to affect climate change and air pollution because both of them have important direct effects on the radiation balance of the earth. In this paper, we study the ability of Cloud Aerosol LIDAR and Infrared Pathfinder Satellite Observation (CALIPSO) data to detect, locate and distinguish between cloud and aerosol layers in the atmosphere over Peninsula Malaysia. We also used image processing technique to differentiate between cloud and aerosol layers from the CALIPSO images. The cloud and aerosol layers mostly are seen at troposphere (>10 km) and lower stratosphere (>15km). The results shows that CALIPSO can be used to determine cloud and aerosol layers and image processing technique has successfully distinguished them in the atmosphere.

An initial assessment of the CALIPSO lidar data on stratospheric aerosol backscatter coefficients over peninsular Malaysia

Remote sensing using the satellite borne LIDAR systems are currently providing new features for global atmospheric sensing from space. The LIDAR on board the Cloud Aerosol LIDAR and Infrared Pathfinder Satellite Observation (CALIPSO) satellite is currently obtaining global aerosol and cloud measurements from space since launched on April 28, 2006. The CALIPSO satellite carries a polarization-sensitive LIDAR system that records backscatter measurements at 532 nm and 1064 nm. In this study, we investigated the stratospheric aerosol backscatter coefficients over Peninsular Malaysia. An initial result of actual data supports that the CALIPSO LIDAR data exhibits sensitivity to the presence of stratospheric aerosol in this study area.

Water quality and Sea Surface Temperature mapping using NOAA AVHRR data

Environmental pollution is coeval with the appearance of humans. Water pollution problem becomes increasingly critical in this present-day, whether in developed or developing countries. Sediment is the primary cause of water pollution. The environmental pollution problem can be measured using ground instruments such as turbidity meters for water measurements. Field measurements cannot provide fine spatial resolution maps with detailed distribution pattern over a large study area. The study was carried out to verify the validity of National Oceanic and Atmospheric Administration Multi-Channel Sea Surface Temperature (SST) (NOAA MCSST) algorithm by NOAA at South China Sea. SST is verified by comparing the SST calculated by algorithm with sea-truth data collected by Research on the Sea and Islands of Malaysia (ROSES). ROSES had travelled and collected data at South China Sea from 26 Jun 2004 to 1 August 2004. In this study the transmittance function for each band was modeled using the MODTRAN code and radiosonde data. The expression of transmittance as a function of zenith view angle was obtained for each channel through regression of the MODTRAN output. The in-situ data (ship collected SST values) were used for verification of results. The derived SST value was compared with the ground truth data collected during Research on the Seas and Islands (ROSES) project and the standard deviation is less than 1 degree Celsius. SST map was created and comparison between the in-situ SST patterns was made in this study. The satellite NOAA AVHRR data used in SST analysis was used for water quality mapping. The DN values were converted into radiance values and later reflectance values - AVHRR Radiometric Correction and Calibration. The reflectance values corresponding to the ground truth sample locations were extracted from all the images. In this study, the multidate data were corrected to minimize the difference in atmospheric effects between the scenes. The reflectance values for window size of 3 by 3 were used because the data set produced higher correlation coefficient and lower RMS value. Finally, an automatic geocoding technique from PCI Geomatica 10.1 - AVHRR Automated Geometric Correction was applied in this study to geocode the SST and TSS maps.

PM10 RETRIEVAL OVER THE WATER SURFACE OF PENANG STRAITS FROM LANDSAT TM5 DATA

In this study, we used the Landsat TM data captured on 9 March 2006 for the retrieval of PM10 over the water surface of Penang Straits, Malaysia. PM10 measurements were collected using a handheld DustTrakTM meter simultaneously with the remotely sensed data acquisition. The PCI Geomatica version 9.1 digital image processing software was used in all image-processing analysis. An algorithm was developed based on the atmospheric optical characteristic. The digital numbers were extracted corresponding to the ground-truth locations for each band and then converted into radiance and reflectance values. The reflectance measured from the satellite [reflectance at the top of atmospheric, &rgr;(TOA)] was subtracted by the amount given by the surface reflectance to obtain the atmospheric reflectance. Then the atmospheric reflectance was related to the PM10 using regression analysis. These atmospheric reflectance values were used for calibration of the PM10 algorithm. The developed algorithm was used to correlate the digital signal and the PM10 concentration. The proposed algorithm produced a high correlation coefficient (R) and low root-mean-square error (RMS). The PM10 concentration was generated using this algorithm over the water surface of Penang straits.

Assessment of atmospheric optical thickness measured by handheld spectroradiometer for air pollution studies

This study was conducted to observe the sky radiation for air quality retrieval from spectroradiometer measurements over USM campus. The objective of this study is to evaluate the performance of a spectroradiometer for providing useful remotely sensed data for air pollution studies. Aerosol optical thickness (AOT) values were derived from the atmospheric transmittance measurements. A well known Beer-Lambert-Bouguer law was applied to obtain aerosol optical thickness (AOT) from the atmospheric transmittance. Finally, the AOT map was generated using Kriging interpolation technique. This paper demonstrates the application of spectroradiometer data to retrieve AOT values in USM campus, Penang, Malaysia.

Regional land use/cover classification in Malaysia Based on conventional digital camera imageries

This paper presents an economical analysis of land cover in Malaysia. Land cover classification from remotely sensed data is an important topic in remote sensing applications. We attempted to investigate the feasibility of using a conventional digital camera for acquiring high resolution imagery for land use/cover mapping. The objective of this study is to test the high-resolution digital camera imagery for land cover mapping using remote sensing technique. The study area is the Merbok River estuary, Kedah and Timah Tasoh Lake, Perlis, both located in Peninsular Malaysia. The digital images were taken from a low-attitude light aircraft. A Kodak camera, model DC290, was used to capture images from an elevation of 8000 feet on board Cessna 172Q. The use of a digital camera as a sensor to capture digital images is cheaper and more economical compared to the use of other airborne sensors. This technique overcomes the problem of the difficulty in obtaining cloud-free scenes in the Equatorial region from a satellite platform. The images consisted of the three visible bands-red, green, and blue. Supervised classification technique (Maximum Likelihood, ML, Minimum Distance-to-Mean, MDM, and Parallelepiped, P) was applied to the digital camera spectral bands (red, green and blue) to extract the thematic information from the acquired scenes. The accuracy of each classification map produced was validated using the reference data sets consisting of a large number of samples collected per category. The results produced a high degree of accuracy. This study indicates that the use of a conventional digital camera as a sensor in remote sensing studies can provide useful information for planning and development of a small area of coverage

Water quality mapping using Landsat TM imagery

Environmental monitoring through the method of traditional ship sampling is time consuming and requires a high survey cost. The objective of this study is to evaluate the feasibility of Landsat TM imagery for total suspended solids (TSS) mapping using a newly developed algorithm over Penang Island. The study area is the seawater region around Penang Island, Malaysia. Water samples were collected during a 3-hour period simultaneously with the satellite image acquisition and later analyzed in the laboratory above the study area. The samples locations were determined using a handheld GPS. The satellite image was geometrically corrected using the second order polynomial transformation. The satellite image also was atmospheric corrected by using ATCOR2 image processing software. The digital numbers for each band corresponding to the sea-truth locations were extracted and then converted into reflectance values for calibration of the water quality algorithm. The proposed algorithm is based on the reflectance model that is a function of the inherent optical properties of water, which can be related to its constituents concentrations. The generated algorithm was developed for three visible wavelenghts, red, green and blue for this study. Results indicate that the proposed developed algorithm was superior based on the correlation coefficient (R) and root-mean-square deviation (RMS) values. Finally the proposed algorithm was used for TSS mapping at Penang Island, Malaysia. The generated TSS map was colour-coded for visual interpretation and image smoothing was performed on the map to remove random noise. This preliminary study has produced a promising result. This study indicates that the empirical algorithm is suitable for TSS mapping around Penang Island by using satellite Landsat TM data.

A satellite AOT derived from the ground sky transmittance measurements

The optical properties of aerosols such as smoke from burning vary due to aging processes and these particles reach larger sizes at high concentrations. The objectives of this study are to develop and evaluate an algorithm for estimating atmospheric optical thickness from Landsat TM image. This study measured the sky transmittance at the ground using a handheld spectroradiometer in a wide wavelength spectrum to retrieve atmospheric optical thickness. The in situ measurement of atmospheric transmittance data were collected simultaneously with the acquisition of remotely sensed satellite data. The digital numbers for the three visible bands corresponding to the in situ locations were extracted and then converted into reflectance values. The reflectance measured from the satellite was subtracted by the amount given by the surface reflectance to obtain the atmospheric reflectance. These atmospheric reflectance values were used for calibration of the AOT algorithm. This study developed an empirical method to estimate the AOT values from the sky transmittance values. Finally, a AOT map was generated using the proposed algorithm and colour-coded for visual interpretation.