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.
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