capabilities when compared to traditional photogrammetry. For
example, airborne laser mapping systems can penetrate forest
canopy to map the floor beneath the treetops, accurately map
the sag of electrical power lines between transmission towers or
provide accurate elevation data in areas of low relief and
contrast such as beaches. Airborne laser mapping is a non-
intrusive method of obtaining detailed and accurate elevation
information. It can be used in situations where ground access is
limited, prohibited or risky to field crews. Since the
instruments are less sensitive to environmental conditions such
as weather, sun angle or leaf on/off conditions, the envelope for
survey operations is increased. In addition, airborne laser
mapping can be conducted at night with no degradation in
performance.
Commercial airborne laser instruments are now available from
several instrument manufacturers while various survey
companies have designed and built proprietary sensors. A
number of service providers are operating these instruments
around the world, either for dedicated survey needs or for hire
on a project basis. (See www.airbornelasermapping.com for a
complete directory.) Some organizations are starting to survey
areas on speculation and then offering the laser-generated data
sets for resale similar to the satellite data market. While the
basic principles and design constraints of airborne laser
altimetry are well-known (Wehr and Lohr, 1999; Baltsavias,
19993), there is still significant variation in design from
instrument to instrument, especially across custom-designed
sensors. The general characteristics and specifications of the
current generation of commercial systems are summarized in
Table 1.
International Archives of Photogrammetry and Remote Sensing, Vol. 32, Part 3W14, La Jolla, CA, 9-11 Nov. 1999
Specification Typical Value
Wavelength * 1.064 um
Pulse Repetition Rate 5-15 kHz (25 kHz max)
Pulse Energy 100s uJ
Pulse Width 10 ns
0.25 - 2 mrad
40? (75? max)
Beam Divergence
Scan Angle (full angle)
Scan Rate 25 - 40 Hz
Scan Pattern Zig-zag, parallel, elliptical,
sinusoidal
GPS Frequency 1-2
INS Frequency 50 (200 max)
Operating Altitude 500 - 1000 m (6000 m max)
Footprint 0.25 - 2 m (from 1000 m)
Multiple Elevation Capture 2-5
Grid Spacing 0.5-2m
Accuracy (elevation) 15+ cm
Accuracy (planimetric) 10-100 cm
Post-Processing Software ® ^ Proprietary
Price (standard) $0,850k - $1,000k
Price (custom) $1,000k - $2,000k
Delivery (standard) 20 - 26 weeks
generally diode-pumped Nd:Y AG, Nd:YLF and Nd:YVO, although
there are some systems operating at 1.5 um
refers to geo-referencing of laser slant ranges to an established
reference frame, normally WGS84
Table 1. Characteristics of Typical Commercial Systems
Intensity capture of the return pulse, either through waveform
digitization or return pulse peak capture, is becoming
increasingly common on commercial instruments and will
become a standard feature within the next 12 - 18 months.
Additional data analysis capabilities such as automatic feature
extraction are also being developed. Improvements to the
sensor designs, added capabilities such as fully integrated
digital cameras and increased reliability/decreased operating
costs are all under consideration by the commercial sector.
3. INSTALLED INSTRUMENT BASE
It is instructive to look at the recent growth of the installed
instrument base to help predict future trends in the commercial
deployment of laser altimetry.
3.1. Adoption Curve
While research and scientific laser altimetry systems have been
deployed for many years by government and academic
institutions, it is only recently that there has been a large growth
in the number of commercial organizations operating such
instruments on a "for profit" basis. As a new technology, the
adoption curve - the rate at which airborne laser altimetry is
being deployed and accepted as a standard operational tool in
the commercial sector - is an important indicator to review. It
provides insight into trends in the implied demand for services
based on the technology. It can also be used as the basis for
estimating the projected instrument base and the resulting
competitive environment for survey companies using airborne
laser altimetry. A review of the commercial sector since 1995
shows the number of installed instruments has been increasing
rapidly over the past five years. A breakdown of the annual rate
at which commercial firms have taken delivery of instruments,
either OTS or proprietary designs, is presented in Table 2. The
numbers clearly demonstrate significant year-over-year growth
in the installed instrument base.
Year #instruments % base
1995 3 8%
1996 6 16%
1997 2 5%
1998 9 24%
1999 18 47%
Total by Jan 1st 2000 38 100%
Table2. Installed Instrument Base by Year
Since 1995, the number of laser altimeters deployed and
operating in the commercial sector has increased from 3 to 38,
with a significant percentage of this growth occurring since
1997. The 38 sensors listed in Table 2 represent a capital
investment of ~$30M - $35M based on current pricing levels,
allowing for reduced costs in proprietary instruments compared
to OTS systems. Significantly, 47% of the systems currently
operating in the field were delivered in 1999 with 70% of the
installed instrument base having been deployed since January
Interne
1998. Table 3 «
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projected orders
Year
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Total by Jan
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January 1, 2000.
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TopEye
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Total
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Table 4.
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