The aim of this work is to develop informative and convenient products that can be generated from the LiDAR and imagery data for a power utility company. The objectives are listed as follows:
•To create a land cover map within the area of interest (AOI) based on traditional photo interpretation;
•To find out the current conditions of wires (e.g. sagging);
•To find out the differences of height between the transmission line and objects above the ground (e.g. vegetation).
The purpose of the study is to demonstrate the potential of the LiDAR technology to improve the reliability of the electric transmission system by preventing vegetation related outages. LiDAR and imagery data can provide the power utility company documentation that identifies areas that do not meet required standard for vegetation separation from the wires. LiDAR will allow the power utility company to review current conditions and to plan vegetation management work, while minimising the need for in situ survey.
Using the 2009 acquired Light Detection and Ranging Data (LiDAR) having an approximate resolution of 1 point/m2, and geometrically accurate aerial photography having spatial resolution of 19 cm, we were able to establish the following quantitative characteristics of the high voltage transmission line located in the southern part of the Brunei and Muara District, Brunei Darussalam (Figure 2).
The profile for the power utility company transmission line highlighted in the AOI is shown in Figure 3. The total length of the line is 7032.75 meters. The highest recorded by the LiDAR point of the line (including towers) is 40.56 meters above the ground, which is located at 574089.769 Easting and 534138.781 Northing (GDBD/BRSO2009), and it belongs to one of the towers.
There are a total of 24 towers supporting the transmission line. There are four wires in the vertical plane. The vertical planes are separated by the distance approx. 7.7 meters.
The data used in this study entailed the following:
The orthopohoto is an aerial photo that has been corrected geometrically. The data were collected in 2009 and has a resolution of 19 cm.
The data were collected in 2009. It has a resolution of 1 point/m2 and contains the x, y and z coordinates, where
x refers to Eastings
y refers to Northings
z refers to the elevation above mean sea level
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Figure 1. Transmission line as seen by LiDAR
The following summarises the method used for this study and Figure 2 depicted the workflow for this study.
Preparation of LiDAR and orthophoto data.
Create a classified Land Cover Map.
Convert LiDAR point data into raster.
Create graphs to show the profile of the transmission line.
Figure 2. Data Processing flowchart
Analysis and Results
The land cover map shown in Figure 3. was categorized into six classes namely, agriculture, low vegetation, road, tower, trees and water/river. The classification of various land cover type was done within the selected buffered area. Each land cover type was represented in different colors so that it is easy to distinguish the distinctive land cover. The land cover map could also be used to develop an in-depth study on the vegetation management strategy and other technical, quantitative studies of interests, e.g., vehicle access study. Here, we just demonstrate that this type of data can be extracted from orthophotos.
Figure 3. Land Cover Map of selected the power utility company's asset. In this map, we only chose a fragment of the transmission line which is located in the western part to show the distinctive land cover classes.
Figure 4. A fragment of the transmission line including one of the towers.
Figure 4. shows a selected section of the transmission line. The wires are marked as red polka dots. The blue line is the line provided by the power utility company. Clearly, the line does not represent the centraline of the wires as it should be.