Transcript
LiDAR Applications in
Surveying and Engineering
2013 NC GIS Conference
Raleigh, NC
Frank A. “Alex” Rankin, III PE, PLS
What is LiDAR?
• Light Detection and Ranging
• Analogous to RADAR, but using a different part
of the electromagnetic spectrum
• RADAR uses radio waves or microwaves
What is LiDAR?
• LiDAR uses light at or near the visible spectrum
(Visible spectrum occupies 390 nm - 700 nm)
• Aerial mapping LiDAR generally uses 1064 nm
Yttrium-Aluminum-Garnet lasers
What is LiDAR?
• LiDAR uses the laser to illuminate a target and
then analyzes the reflection
• The narrow laser beam makes it possible to map
objects with a high degree of resolution
What is LiDAR?
• The basic technology has been around
since the 1970s, but ---
• Because of size, cost and complexity had
limited (government) application, but ---
• Recent dramatic advances in laser and
detection technology, computational
speed, and memory storage have made
commercial applications possible
What is LiDAR?
• Smaller, faster, smarter LiDAR makes
possible direct measurement of complex
and hard to access structures
What is LiDAR
• Depending on the wavelength laser used, LiDAR can develop 3D point clouds of a wide range of objects, such as – rocks, non-metallic objects, rain, chemical compounds, aerosols, clouds, and even single molecules
What is LiDAR
• For Surveying and Civil Engineering the
most important applications are aerial
scanning and terrestrial scanning
What is LiDAR
• Terrestrial Scanning creates 3D models of
complex objects: piping networks,
roadways, archeological sites, buildings,
bridges, etc.
What is LiDAR
• One of the advantages of Terrestrial Lidar
is that objects can be measured remotely
making operations such as measuring
roadways under traffic much safer.
What is LiDAR
• Aerial Scanning has many uses - measuring agricultural productivity, distinguishing faint archeological remains, measuring tree canopy heights, determining forest biomass values, advancing the science of geomorphology, measuring volcano uplift and glacier decline, measuring snow pack, and providing data for topographic maps - to name a few…
Topographic Mapping
• In the past decade,
because of the
advantages of LiDAR,
it has largely
displaced
Photogrammetry as
the process for
development of large
scale topographic
maps
Topographic Mapping
(LiDAR Advantages)
• LiDAR sensors can
be operated in any
weather – (not so with
cameras- the clouds
get in the way)
• LiDAR sensors are
not affected by low
sun angles - which
would prevent useful
photos
Topographic Mapping
(LiDAR Advantages)
• IN FACT – LiDAR can
actually operate at
night!
• More hours of useful
flying per day means
LiDAR offers greater
efficiency, faster
results, and can cover
more ground than
photogrammetry
Topographic Mapping
(LiDAR Advantages)
• Rural and remote
areas are easier and
quicker to survey with
LiDAR because each
point has geo-
referenced location
and elevation – no
orthorectification of
image – no network of
photo panels required
Topographic Mapping
(LiDAR Advantages)
• Photogrammetry needs to be able to see the ground to create contours
• LiDAR returns come from every object illuminated – the lowest being the ground – wherever the sunlight hits LiDAR will return XYZ
Topographic Mapping
(LiDAR Advantages)
• LiDAR creates a 3D model directly from the returns
• Photogrammetry requires the incremental comparison of
a pair of stereoscopic photographs – indirect and much
more labor intensive
Topographic Mapping
(LiDAR Advantages)
• Photogrammetry requires contrast to see ground surfaces – desert, wetlands, beaches, coasts are difficult or impossible
• LiDAR results come directly from the returned signal – contrast not required
Public LiDAR Resources
• Public sources of existing LiDAR are
valuable resources for engineering and
surveying firms – some addresses are:
• http://www.ncfloodmaps.com/
• https://connect.ncdot.gov/resources/gis/Pa
ges/Cont-Elev_v2.aspx
• http://www.nconemap.com/
Public LiDAR Resources
• These public sources are excellent for
large scale planning processes…
However……!
Public LiDAR Resources
• North Carolina
Board of
Examiners for
Engineers and
Surveyors,
says….
….in its Spring 2012
newsletter…
Public LiDAR Resources
“As to the use
of…floodplain
mapping LiDAR
elevation data should
not be used for final
design…” or it
“…could lead to
disciplinary
action…”
Public LiDAR Resources
• But properly used these public sources provide
the base information for all types of planning
processes, such as – developing project specific
hydrology models for large areas…
Public LiDAR Resources
• …or for developing
land use plans for
large residential,
commercial,
industrial, or mixed
use areas….
Public LiDAR Resources
• …..or for view sheds
for parks, trails, and
other large outdoor
recreational areas….
Public LiDAR Resources
• ….evaluating the relationship to environmental
sites….
Public LiDAR Resources
• …planning for greenways and other recreational
amenities….
Public LiDAR Resources
• …planning industrial sites….
Public LiDAR Resources
• …industrial site selection by “site selection
consultants” (hired guns)….
Public LiDAR Resources
• …and beyond initial planning the public sources
can be used for large scale schematic grading
exercises…
LiDAR in Civil/Surveying Firm
• Terrestrial LiDAR (Scanning) can rapidly map complex sites in much more detail than is possible with conventional means – this makes a better base sheet for design….
LiDAR in Civil/Surveying Firm
• …and even if not complex, it covers areas that
are large (but too small to fly) quickly….
LiDAR in Civil/Surveying Firm • Imagine a building – filled with piping….
LiDAR in Civil/Surveying Firm • …imagine crawling around that piping trying to
locate it by direct measurement…
LiDAR in Civil/Surveying Firm
• …and
the cost
(and
time)
savings
become
obvious.
LiDAR in Civil/Surveying Firm
• For larger
areas, site
specific aerial
LiDAR provides
base sheets for
all types of
project specific
civil engineering
design…such
as…
LiDAR in Civil/Surveying Firm
• …Master
Planning…
LiDAR in Civil/Surveying Firm
…Grading...
LiDAR in Civil/Surveying Firm
…Utilities...
LiDAR in Civil/Surveying Firm
…Drainage Analysis….
LiDAR in Civil/Surveying Firm
…Erosion Control and Stormwater Treatment…
LiDAR in Civil/Surveying Firm
…Roadway
Design…
LiDAR in Civil/Surveying Firm
…and much, much, more.
The End!
LiDAR in Civil/Surveying Firm
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