9-11 Nov. 1999 
that is large enough to 
such markets require the 
ties provided by laser 
le from other survey 
us economic factors to 
ita products. Potential 
hed client-base with the 
laser altimetry survey 
ble price. Due to the 
he technology to the 
markets are still being 
, laser altimetry can be 
| competitive technology 
methods. | For many 
is currently deployed in 
onal sensors including 
cameras, hyperspectral 
al, laser altimetry is best 
sensing toolbox that can 
oducts produced, either 
1 other sensor systems. 
ithin a field survey can 
n project specific goals 
ual client has particular 
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ns without support from 
, in certain applications, 
g, laser altimetry offers 
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applications is provided 
utelius, 1997; Gutelius, 
apping is a rapid, cost- 
h-density elevation data 
ping applications. The 
oraphic surveys to be 
reduced cost compared 
mapping in the forestry 
rcial areas investigated. 
| topography beneath the 
oth the forestry industry 
rate information on tree 
ormation that is difficult 
iques. Airborne laser 
itellite imaging, can 
1 the tree canopy as well 
of the data allows the 
yzed and classified as 
"IMs of the bare ground 
ative tree heights to be 
‘om the research sector 
' return laser pulse to 
Blair and Hofton, 1999) 
s the technology gains 
acceptance in the commercial sector. Consequently, airborne 
laser mapping is an extremely effective technique for forestry 
companies when compared to photogrammetry or extensive 
ground surveys. 
Coastal Engineering: Beach mapping or similar surveys of 
coastal regions are another area where airborne laser technology 
offers state-of-the-art type performance with significant 
advantages over existing survey techniques. Since traditional 
photogrammetry is difficult to use in areas of limited contrast, 
such as beaches and coastal zones, an active sensing technique 
such as laser altimetry offers the ability to complete surveys that 
would be too costly using other methods. In addition, highly 
dynamic environments such as coastal zones often require 
constant updating of baseline survey data. Airborne laser 
mapping offers a cost-effective method to do this on a routine 
basis. It is also used for mapping and monitoring of shore 
belts, dunes, dikes and coastal forests. 
Corridor or Right-of-Way Mapping: Airborne laser mapping 
allows rapid, cost-effective, accurate mapping of linear 
corridors such as power utility right-of-ways, gas pipelines, or 
highways. A major commercial market is mapping power line 
corridors to allow for proper modeling of conductor catenary 
curves, sag, ground clearance, encroachment and accurate 
determination of tower locations. For example the use of data 
acquired through airborne laser surveys can be combined with 
simultaneous measurements of air and conductor temperature 
and load currents to establish admissible increases in load- 
carrying capacity of power lines. 
Flood Plain Mapping: Accurate and updated modeling of 
flood plains is critical both for disaster planning and insurance 
purposes. Airborne laser mapping offers a cost-effective 
method of acquiring the topographic data required as input for 
various flood plain modeling programs. As part of its Map 
Modernization Plan, the Federal Emergency Management 
Agency (FEMA) in the U.S. is currently performing an 
assessment of advanced technologies including laser altimetry 
for possible use in the preparation of National Flood Insurance 
Program (NFIP) maps and related products. FEMA has 
recently released guidelines which present specifications that to 
be used for the application of laser altimetry systems for 
gathering the data necessary to create digital elevation models 
(DEMS), digital terrain maps, and other NFIP products. 
Urban Modeling: Accurate digital models of urban 
environments are required for a variety of applications 
including telecommunications, microclimate modeling, wireless 
communications, law enforcement and disaster planning. An 
active remote sensing system such as a laser offers the ability to 
accurately map urban environments without some of the 
disadvantages of other technologies. 
Disaster Response and Damage Assessment: Major natural 
disasters such as hurricanes or earthquakes stress an emergency 
response organization's abilities to plan and respond. Airborne 
laser mapping allows timely, accurate survey data to be rapidly 
incorporated directly into on-going disaster management efforts 
and allows rapid post-disaster damage assessments. It is 
particularly useful in areas prone to major topographic changes 
International Archives of Photogrammetry and Remote Sensing, Vol. 32, Part 3W14, La Jolla, CA, 9-11 Nov. 1999 
during natural disasters; areas such as beaches, river estuaries 
or flood plains. 
Wetlands and Other Restricted Access Areas: Many 
environmentally sensitive areas such as wetlands offer limited 
ground access and due to vegetation cover are difficult to assess 
with traditional photogrammetry. Airborne laser altimetry 
offers the capability to survey these areas. The technology can 
also be deployed to survey toxic waste sites or industrial waste 
dumps. 
In addition to the commercial applications discussed above, 
various efforts are under way to investigate other application 
areas where airborne laser altimetry may offer significant 
advantages. 
22 Commercial Instruments 
The current generation of commercial airborne laser altimetry 
instruments use a combination of three mature technologies; 
rugged compact laser rangefinders (LIDAR), highly accurate 
inertial reference systems (INS) and the global positioning 
satellite system (GPS). By integrating these subsystems in to a 
single instrument, it is possible to rapidly produce accurate 
digital topographic maps of the terrain beneath the flight path of 
the aircraft. Similar to aerial cameras, the instruments can be 
installed in small single or twin-engine planes or helicopters. 
For commercial surveys, the absolute accuracy of the laser- 
derived elevation data is generally quoted as 15 cm; relative 
accuracy less than 5 cm. Absolute accuracy of the planimetric 
data is dependent on operating parameters such as flight 
altitude but is usually quoted at decimeter to meter levels. 
Accuracy tends to degrade with terrain slope, roughness and 
vegetation cover resulting in generally lower accuracy than 
quoted assuming a smooth, flat surface. To date there have 
been limited independent studies published that verify the 
accuracy claims of commercial operators (Huising and Gomes 
Pereira, 1998; Kraus and Pfeifer, 1998). However, there is a 
growing body of work by independent agencies such as the 
USGS, FEMA and similar agencies in Europe that indicates 
these levels of absolute accuracy are achievable, but only if 
commercial operators are rigorous in their attention to 
calibration of their instruments and implement appropriate 
QA/QC procedures on the laser data. 
With current commercial instruments, elevation data is 
generated at 1000s of points per second, resulting in elevation 
point densities far greater than traditional ground survey 
methods. One hour of data collection can result in over 
10,000,000 individually geo-referenced elevation points. With 
these high sampling rates, it is possible to rapidly complete a 
large topographic survey and still generate DTMs with a grid 
spacing of 1 m or less. With current commercial systems it is 
possible to survey one thousand square kilometers in less than 
12 hours and have the geo-referenced DTM data available 
within 24 hours of the flight. A 500-kilometer linear corridor, 
such as a section of coastline or a transmission line corridor can 
be surveyed in the course of a morning, with results available 
the next day. Airborne laser mapping instruments are active 
sensor systems, as opposed to passive imagery such as cameras. 
Consequently, they offer advantages and unique commercial