Archives for March 10, 2015

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The word “Kampung” or village is always referred to remote area, calm environment and accommodated by citizens that reach their golden ages. Inevitably this word is always come together with the perception of under-developed area with people that commonly less exposed to the modern-age activities in urban area. Our aim is to revolutionize the true meaning of Kampung which originally refers to the place which you feel belong most and proud of. The theme “KampungKu” aims at strengthening the feeling of love and awareness of each Malaysian towards our country in general and their hometown specifically. The main theme for the short video “KampungKu” can be further articulated into several sub-themes as follows:

1. Multi-racial nation
2. Unique tropical flora and fauna
3. Food
4. Tourism
5. Property and real estate
6. Development and economy

Visit our KampungKu FB page

Special lecture given by PM Shafie on the history of fght and UTM…

Aerodynamic roughness length (zo) and zero plane displacement (d) of land surfaces are among essential variables for the parameterization of momentum and heat exchanges.

Airborne LiDAR data has been one of the reliable data for individual tree properties estimation. High density airborne LiDAR data has been used previously for detailed reconstruction of tree geometry. The aim of this study is to estimate aerodynamic roughness over specific height (Z_o/H) and zero plane displacement (d_o) over forest area using airborne LiDAR data. The results of this study will be very useful as a main guideline for related applications to understand the role of carbon and hydrological cycles, land cover and land use change, habitat fragmentation, and biogeographical modeling. The airborne LiDAR data is first classified into ground and non-ground classes. The ground points are interpolated for digital terrain model (DTM) generation and the non-ground points are used to generate digital surface model (DSM). Canopy height model (CHM) is then generated by subtracting DTM from DSM. Individual tree delineation is carried out on the CHM and individual tree height is used together with allometric equation in estimating height to crown base (HCB) and diameter at breast height (DBH). Tree crown delineation is carried out using the Inverse Watershed segmentation approach. Crown diameter, HBC and DBH are used to estimate individual tree frontal area and the total frontal area over a specific ground surface is further calculated by subtracting the intersected crowns and trunks from the total area of tree crowns and trunks. The considered ground area i.e. plants area determined the final spatial resolution of the Z_o/H and d_o. Both parameters are calculated for different wind directions that were assumed to be originated from North/South and East/West. The results show that the estimated Z_o/H and d_o have similar pattern and values with previous studies over vegetated area.

Abstract

This research presents an accuracy assessments of Digital Elevation Model (DEM) generated over different slope class and percentage of canopy density in district of Bentong, Pahang, Malaysia. Basically, LiDAR system is an ideal technique to derive DEM in any area including forest or vegetation area. However, some clients will ask so many questions especially related to the accuracy that should be answered. By having this kind of sensitivity, this study is carried out with the aim is to evaluate the accuracy of LiDAR derived DEM based on different slope class and different percentage of canopy density. In order to achieve this aim, several objectives have been determined such as reviewing from the previous research about this issue, performing LiDAR filtering process and identifying the slope and canopy density of the study area, and evaluation the accuracy of DEM. The slope of the study area is divided into class-1 (0-5 degrees), class-2 (5-10 degrees), class-3 (10-15 degrees) and class-4 (15-20 degrees). The results show that the slope class has high correlation (0.916) with the RMSE of the LiDAR ground points. The percentage of crown cover is divided into class-1 (60-70%), class-2 (70-80%), class-3 (80-90%) and class-4 (90-100%). The correlation between percentage of crown cover and RMSE of the LiDAR ground points is slightly lower than the slope class with the correlation coefficient of 0.663.

Research aim and objectives

The aim of this study is to investigate the effect of slope and canopy percentage towards the accuracy of LiDAR derived DEM.

Study area

In this study, the study area that has been chosen is located at Simpang Pelangai, Bentong, Pahang. The area of this places is about 200 m x 100 m and geographically it is located at 3ᵒ10’12.62” North, 102ᵒ11’37.67” East. Figure below shows the Google Earth image of this study area.

Data Processing

In order to assess the accuracy of LiDAR data, several processes have been carried out by using specific software such as Microstation V8 (TerraScan) and ArcGIS 10.1 software. Among the related processes have been performed such as ground filtering process, DEM interpolation, slope map creation, and canopy density determination. Figure below shows the flowchart of the data processing in this study.

Result

The effect of terrain slope on airborne LiDAR elevation:

The effect of canopy density on airborne LiDAR elevation:

Generally, the RMSE values will increases by increasing the slope and density of the canopy. However, Slope can be consider as more influence factor on the error in point clouds elevation. This has been proven by comparing the correlation coefficient for both of the factor where slope is highly correlated in introducing the error to the point clouds compare to canopy.