Archives for March 2015

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.

A group of researchers in Utah, home of the finest powder snow on earth (and I speak from direct experience) has developed a system to report on the snowfall conditions during storms. The research originally supported by the National Science Foundation (NSF) is now being commercialized with the intent of selling the camera – based system to the DOTs.

Using fundamental precipitation research from atmospheric scientist Timothy Garrett, who developed the original multi-angle snowflake camera with Cale Fallgatter, the technology can resolve falling particles down to the diameter of a human hair and also measure the speed at which they fall.

“The funding to Fallgatter Technologies will allow them to demonstrate an important new tool to better understand weather conditions in real-time,” says Ben Schrag, NSF Small Business Innovation Research program director. “And will hopefully help local authorities and meteorologists to make better decisions with regards to severe weather.”

– See more at: http://blog.lidarnews.com/#sthash.uAlMARnL.dpuf

Source: http://blog.lidarnews.com/

The points clouds obtained from Airborne LiDAR data can be used at certain extent for direct measurement of tree attributes for example diameter at breast height. The filtering process is a must to remove understorey vegetation.

The histogram-based individual tree filtering has been introduced for this purpose.

Non-destructive Laser-based Individual Tree Aboveground Biomass Estimation in Tropical Rainforest

Introduction

Research community mainly in forestry related applications have been exposed with numerous biophysical datasets from satellite imagery. However, these kind of datasets are not supported by accurate field measurements data that causes uncertainty in derived datasets. Terrestrial laser scanning (TLS) is a ground-based LiDAR technology that can be used to retrieve highly detailed 3-dimensional vegetation structure. For plot level forest measurement, TLS could assist the estimation of several useful tree parameters for example tree number and position, tree height, diameter at breast height (DBH), tree volume, above ground biomass and so on. Furthermore, Terrestrial TLS has huge potential to provide accurate tree structure including how the foliage and stems are arranged above the ground of a specific tree. This study aims at estimating individual tree aboveground biomass from high density point cloud obtained by terrestrial laser scanner (TLS). The point clouds were obtained together with field measurements data in 30 forest plots covering 604 trees over tropical rainforest landscape in Royal Belum State Park, Perak, Malaysia. Tree parameters such as Diameter at breast height (DBH), tree height and height to crown base were estimated from TLS for assessment of individual tree measurements. Tree parameters such as stem, branches and leaves volume were estimated from TLS to derive aboveground biomass through volume to biomass conversion factors.  Cylinder fitting was applied on the point cloud of the tree stem for DBH and stem volume measurements. Tree height and height to crown base are computed using histogram analysis of the point clouds elevation. Tree branches and leaves volume is estimated by fitting a concave-hull. The results were assessed using other allometric-derived aboveground biomass.

 

Research objective

The main objectives of this research is to estimate the above-ground biomass using non-destructive laser scanning approach for selective tree species in Malaysia’s tropical rainforest.

 

Study Area

This study is carried out at the northern part of Peninsular Malaysia in Royal Belum State Park, Gerik in the state of Perak. The coordinate of the area is around 5º 33’ 25.68” N and 101º38’29.41” E, located at 230km away from Ipoh and 430.5km from Kuala Lumpur. This area receiving 1998 to 2300mm of mean annual rainfall, varies throughout the year. According to (WWF-Malaysia 2013), Royal Belum State Park (RBSP) was gazetted as a protected area on 3 May 2007 under the Perak State Parks Corporation Enactment 2001. The park covers a total area of 117,500ha in the most northerly region of the State of Perak in northern Peninsular Malaysia. RBSP lies between border of Thailand on the north, the state of Kelantan to the east and Sungai Gadong in the west. The East-West highway is on its southern border separating the RBSP with Temenggor Forest Reserve to the south. Royal Belum State Park consists of forest, grassland, abandoned agricultural plots, and a large man-made lake, Tasik Temenggor. Forest types found here are mainly lowland dipterocarp, hill dipterocarp and upper dipterocarp. The majority of species are characteristic of tropical rainforest in Peninsular Malaysia, Sumatra and Bornea such as Meranti and Keruing.

 

Data collection

The primary data for this study is high density point clouds data generated from Riegl VZ-400 and the secondary data is the field measured data. These two datasets were taken by UTM@RoyalBelum Scientific expedition on 19^th of September 2014 till 30^th of September 2014.

 

   

 

Raw TLS point cloud data

Images captured from digital camera mounted on TLS during scanning were used to apply color on the registered point clouds. Scan positions and signage for tree identification can be seen clearly from the colorized point clouds to assist in individual tree extraction.

 

 

Individual Tree Extraction

Individual trees were extracted from the registered point clouds. Point clouds from neighbouring trees, understorey and vicinity branches were removed. This process was done manually to get detailed structure of an individual trees.

               

Separation of tree parts

Extracted trees were partitioned into stem, branches and leaves for biomass estimation of every compartment.

 

Reconstructed Trees

Individual trees were reconstructed from cylinders of tree stem and wrapped crown structure as shown below:

Raw point clouds obtained using Terrestrial Laser Scanner. The point clouds were collected using Leica Scanstation C10 laser scanner that operates with the green wavelength at 532nm. This scanner is capable to scan at most 300m distance object with the nominal accuracy of 4.5mm

After registration process, the unnecessary or noise point clouds of those originate from neighbouring trees, understory trees and ground surface are removed to avoid confusion and complexity in data processing. The point clouds are then separated into individual trees for further processing to estimate tree attributes. Further cleaning process of leaf and small branches are required to separate the trunk and branches prior to diameter estimation at different height intervals. The noise removal procedure has been done manually by a careful inspection of every single trees marked in the field as well as in the point clouds.

The geometric reconstruction of individual tree trunk was done by fitting the point clouds with cylinder model at different tree height.

The point clouds of tree crown is wrapped with convex-hull surface. The complete individual tree reconstruction is shown below: