by Brian R. Raber, CMS, GISP, GLS
and Brian Holzworth, GISP
As seen in
charging Ahead
Surveying and remote sensing
capabilities energize the quest
for energy independence.
I
Above: A Merrick
surveyor locates
property corners
as part of a power
line survey.
pob0509 merrick.indd 1
n today’s energy-demanding world, much focus
is being placed on the development of clean and
alternative energy sources. These applications are
creating numerous opportunities for the use of surveying and remote sensing technologies.
In renewables, where energy is generated from
continuously replenished resources such as wind, sun
and geothermal sources, the most obvious application of these technologies lies in the planning, design
and construction of wind and solar farms. Integrating
topographic data with historical climatic and weather
patterns can help identify the optimum locations for
these energy sources, and the transmission of power
from those farms will provide opportunities for typical
route surveying, property ownership research, deed
and easement legal descriptions.
In biofuels, where living and recently dead biological materials such wood, grain and algae are used to
produce energy, remote sensing, survey and geospatial
roles expand the more-traditional services to include
site development of new production plants, market
location analysis, volume of biological material predictions and source-to-user vicinity studies. Initially,
locating and quantifying the volume of biological
materials can be accomplished using multispectral
satellite imagery and hyperspectral sensors, which
detect unique light and reflectance responses from
the source. More traditional surveying and mapping
technologies can be deployed once biofuel plants go
from the concept phase into design and construction
and, finally, distribution since pipelines will be needed
to transport the biofuel to the end-user.
And in the traditional distribution and transmission
field, power producers are looking to push more power
through existing systems and develop new corridors
for the distribution of new energy resources. The use
of more-modern surveying and mapping techniques
such as mobile high-definition scanning and airborne
LiDAR can expedite this type of analysis.
In all of these areas, the development of the infrastructure needed to transmit energy from the producing
source to the end-users will create significant growth
prospects for surveying and mapping professionals.
Combining Surveying and
Remote Sensing
In many cases, the life cycle of a power line project
includes a planning and route-selection phase, an
engineering design phase, a construction phase, and an
operation and maintenance phase. The requirements—
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Powerful Technologies
Figure 1. The life cycle of a power line project.
and challenges—for surveys, maps and geospatial data differ for
each of these phases. Figure 1 illustrates the project life cycle and
provides a few examples of the data and service requirements and
primary issues in each phase.
Planning and Route Selection
The process of determining where to construct transmission
lines has many intricate and interrelated steps. This welldocumented series of processes can be expedited by the use
of modern survey, mapping and remote sensing technologies.
For example, the use of high-accuracy satellite imagery with
submeter pixel resolution, such as the imagery from GeoEye
1, can cover a large corridor of land along a proposed route.
Analyzing the multispectral bands of satellite imagery can also
produce an initial inventory of many land cover and land use
types such as urbanization, natural vegetation and agricultural
land. This data source can provide initial points of access for
geotechnical studies and points of intersection surveys.
Automating the property deeds and plats from the city and
county records can offer quick analysis of the number of landowners that may have to be contacted to enter their property
legally. Many survey CAD and GIS software packages can also
import digital versions of public property records for this initial
planning step. There are several commercially available terrain
data sources that can also be used during the planning phase to
analyze preliminary slope and drainage concerns.
One of the many challenges in traditional and new remote
sensing technologies centers on the word “remote.” During the
initial planning of transmission corridors, traditional survey
methods can take time and can be intrusive on the environment and landowners. Traveling to, from and along a power-line
corridor can add more challenges as landowner relationships
and access to private and public lands are always major issues.
Environmental concerns can contribute to the challenges of
identifying wetlands, endangered plant species and animal
habitat, agricultural land, wet and impassible soils, and heavy
vegetation. Surveyors, remote sensing scientists and mapping
professionals have increasingly begun working together to create
combined solutions to address these types of challenges.
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The Western Area Power Administration (Western) markets
and delivers hydroelectric power and related services within
a 15-state region of the central and western United States.
In its efforts to define future power transmission corridors
and maintain existing power lines, Western relies on aerial
surveys to obtain planimetric, topographic and other thematic data such as wetland delineation. To produce these
databases, Western requires surveyed ground control,
surveyed line crossing data, airborne LiDAR, digital aerial
photography and color infrared photography.
The advances being made in surveying and mapping
technologies fit Western’s mission to create engineering
solutions that combine sound business practices and cost
containment. When Western selected Merrick & Company
to serve as the mapping consultant on a recent project,
the firm combined multiple sensor technologies on one
fixed-wing aircraft to efficiently create the databases
required to design a new transmission line. The technologies included a Leica ALS50 Phase II+ LiDAR system with
multi-pulse-in-air (MPiA) capability, Merrick’s proprietary
Digital Airborne Camera System (DACS), an orientation
system that included a micro intertial reference system
(IRS)/inertial measurement unit (IMU) and a Novatel OEM
airborne GPS device, an AISA Eagle VNIR hyperspectral
sensor, and a variety of weather monitoring equipment.
The LiDAR system was used to create the high-fidelity
digital elevation model used for drainage studies, accessroad design, tower height analysis and line sag modeling.
It also defined catenaries of existing transmission lines
and distribution lines that crossed the new line.
Color digital aerial photography and photogrammetry
were used to produce vector databases. This information
was rectified using the LiDAR elevations, GPS, and IMU
data to create a digital orthophotograph—an aerial photograph that is free of displacement and distortion and
allows for precise measurements and interpretation.
The orientation systems of a GPS and IMU were used to
provide real-world coordinates of the position and attitude
(tip, tilt, yaw and crab) of the aircraft as well as the coordinate values for LiDAR point and photo centers. “Using
LiDAR has helped streamline the way we site transmission
lines by eliminating the need to acquire rights of entry to
survey potential routes,” said Randy Wilkerson, a public
affairs specialist with Western.
The hyperspectral sensor produced a digital picture
comprising 128 discrete images over a broad range of
the light spectrum referred to as a datacube, which stores
information about discrete remotely sensed objects such
as vegetation. The vast amount of information stored in
each pixel of a hyperspectral datacube allowed remote
sensing scientists using sophisticated software to separate the data into discrete land-cover classifications such
as wetlands, endangered plant species and animal habitat. These classifications are possible because each object
Continued on next page.
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Continued from previous page.
on Earth has a fairly unique spectral signature. Below is
an example of wetland determination along a proposed
power line using image processing techniques from hyperspectral data. Such capabilities allow environmental problems to be mitigated quickly and effectively.
GPS surveying techniques were also deployed throughout
the project. First, the geodesist created the control network plan. Next, base station control positions were surveyed so that the airborne sensor data could be “tied” to
real-world coordinates. Elevations were then surveyed in a
variety of land use and land cover locations to validate the
LiDAR ground and line crossing data. And finally, power
pole legs and points of intersection (PIs) along a transmission line were surveyed and staked for final design.
In the past, multiple aircraft mobilizations and numerous ground control points would have been needed to
gather the amount of data that is now collected with
co-mounted sensors on one aircraft and minimal ground
survey work. Western’s objective is to create power transmission opportunities for both traditional and alternative
sources of energy in the most cost-effective and environmentally sound manner. Modern remote sensing technologies provide the opportunity to achieve both goals.
“At Western, we’re always looking at new technologies
to improve how we go about our business and to become
more efficient,” Wilkerson says.
Wetlands polygons automatically
derived using 128-band, 1-meter
hyperspectral imagery.
More-Accurate and Less-Invasive Route Design
Once a preliminary route has been selected, the use of airborne
remote sensing technologies can reduce the “boots on the ground”
impact of the traditional surveyor. The airborne approach alleviates many of the stresses caused by the surveying process since
landowners are often unaware that sensing platforms are present
given the altitudes at which most corridor projects are flown. The
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A Merrick surveyor gathers substation infrastructure details.
use of co-mounted digital aerial photography with
LiDAR is a powerful combination of sensors that
is now being used to produce more-accurate planimetric and topographic databases. These sensors
are oriented to real-world coordinates by a network of ground control check points and control
base stations occupied using GPS during the flight.
Using onboard GPS and inertial measurement unit
(IMU) technologies has also increased the horizontal and vertical accuracy. These airborne orientation technologies reduce the number of ground
control points, which saves time and money. Also,
depending on the accuracy requirements and data
feature content, these sensors can be mounted in
either a fixed-wing aircraft or a helicopter.
Sensors that can accurately identify endangered species, wildlife habitat, soil types and wetlands can also be co-mounted in the air platform.
These additional sensors share the orientation
system with the other mapping sensors so that
all of the information collected during the flight
is coregistered. This recent advance produces
more valuable results for planners, civil engineers,
geologists, hydrologists and environmentalists.
Higher Productivity on the Construction Site
New surveying and mapping technologies—such as survey instruments that combine GPS and total station capabilities—can
increase productivity at the construction site. For example, the
Leica SmartStation offers quicker instrument setup and field
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This fusion of LiDAR elevations and color
digital aerial photography shows power line
structures and power lines. Danger areas
that are encroaching on the power line
right-of-way are shown in red.
LiDAR and digital photography can also
be used to detect whether vegetation and
urban development are encroaching on an
existing power line. The same type of data
is very useful during power load modeling as engineers try to determine whether
more energy can be moved through a given
power line and whether the new line sag is
located too close to vegetation or man-made
objects, which will create danger areas.
A Powerful Future
surveying, which can save time and increase accuracy. Such technologies increase the productivity and reliability of staking transmission line towers and surveying line crossings. Also, mounting a
GPS on a truck or all-terrain vehicle can reduce the time needed
to create terrain data to validate the airborne technologies and asbuilt conditions following construction.
Efficient Operations and Maintenance Mapping Technologies
The use of ground-based laser or high-definition scanners is also
being considered for capturing as-built information on power plants
and existing transmission lines. This high-fidelity information will
assist the operations managers in understanding the current condition of the objects being surveyed. Presently, helicopter-borne sensors are combining LiDAR, digital photography, weather monitors
and high-resolution video to gather data in a single pass over an
existing power line. Unlike a fixed-wing aircraft, helicopters can fly
“low and slow” to literally saturate above-ground objects such as
conductors, towers and vertical obstructions with LiDAR pulses
and thus capture high-resolution imagery.
The American Recovery and Reinvestment
Act stimulus package will push out approximately $32 billion in funding for transmission
line upgrades, the smart grid and renewable
power transmission. These types of initiatives to improve energy
availability and renewability are creating numerous opportunities
for surveyors and mappers in the United States and worldwide. The
integration of multiple sensors on a single airborne platform offers
a plethora of data that—when fused geometrically and relationally—
can provide solutions to environmental, planning, engineering and
social challenges. The ability of surveying and mapping professionals to provide innovative solutions to the many complicated issues
associated with the life cycle of completing a corridor project will
offer both short-term and long-term rewards.
Brian R. Raber, CMS, GISP, GLS, is a certified mapping scientist with ASPRS
and a geographic information system professional with URISA. He is a vice
president of Merrick (www.merrick.com) and has headed the firm’s GeoSpatial
Solutions business unit for 18 years. He can be reached at brian.raber@merrick.com.
Brian Holzworth, GISP, is a project manager for Merrick's GeoSpatial Solutions
business unit. He has more than 20 years of mapping and remote sensing experience and has managed mapping projects in the alternative energy and power
transmission industry. He can be reached at brian.holzworth@merrick.com.
Gary Outlaw, GISP
Merrick & Company
2450 S. Peoria St.
Aurora, CO 80014
gary.outlaw@merrick.com
www.merrick.com
TEL: 303-353-3901
CELL: 303-520-4719
Reprinted with permission from POB Magazine. Copyright May 2009. www.pobonline.com.
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