In: Wagner W., Székely, B. (eds.): ISPRS TC VII Symposium - 100 Years ISPRS, Vienna, Austria, July 5-7, 2010, IAPRS, Vol. XXXVIII, Part 7B 
ALTM ORION: BRIDGING CONVENTIONAL LIDAR AND 
FULL WAVEFORM DIGITIZER TECHNOLOGY 
Valerie Ussyshkin a , Livia Theriault a 
Optech Incorporated, 300 Interchange Way, Vaughan, Ontario, Canada L4K 5Z8 
valerieu@optech.ca. liviat@optech.ca 
KEY WORDS: Data, Digitisation, Forestry, Fusion, LIDAR, Measurement, Modelling, Urban 
ABSTRACT: 
Over the past decade airborne lidar technology has seen the development of new systems capable of digitising and recording the 
entire waveform of each emitted laser pulse through waveform digitisers (WFD). WFD technology holds enormous potential for 
forestry and urban mapping, but the high cost and complexity of data handling and analysis has confined it mainly to research 
institutions. Alternatively, conventional lidar systems used in the commercial lidar sector for high-quality mapping of complex 
targets such as power lines and vegetation have been limited in their ability to collect and record data of sufficient quality for 
sophisticated data analysis, including waveform interpretation. 
This paper focuses on technical characteristics of the ALTM Orion, a new airborne lidar mapper manufactured by Optech 
Incorporated, and in particular, its ability to discriminate consecutive multiple laser returns. Unlike a conventional lidar, the ALTM 
Orion offers fundamentally improved specifications for multiple return data. High-density, multiple return ALTM Orion data with 
unique pulse separation characteristics and exceptional precision might be viewed as a new cost-effective alternative to WFD for 
applications requiring complex target analysis and partial waveform modelling, such as forest research and urban mapping. The new 
technology bears the potential to create an application niche where top-quality dense point clouds, enhanced by fully recorded 
intensity for each return, may provide sufficient information for modelling the received waveforms. Recognizing the importance of 
further development in existing WFD technology, the paper also discusses the possibility of data fusion interpretation and analysis 
tools for both technologies. 
1.0 INTRODUCTION 
Airborne lidar technology has been widely accepted by the 
surveying and mapping community as an efficient way of 
generating high-accuracy spatial data for a variety of 
applications (Renslow, 2005). Unlike two-dimensional aerial 
imagery, the elevation component of airborne lidar data 
provides the inherent ability of this technology to represent 
complex vertical structures and ground surfaces with very high 
precision, which is a prerequisite to most lidar applications, 
many of which focus exclusively on analysis of the elevated 
features (Hudak et al., 2009). 
The capability of an airborne lidar to map complex vertical 
structures and generate high-quality complex target data is 
solely determined by system hardware design. A vast majority 
of airborne lidar sensors currently used in the lidar industry can 
be categorized into two types: discrete return, and waveform. 
Optech has worked extensively with full waveform digitization 
for several decades, and continues with leading-edge algorithm 
development in its current waveform digitizers for ALTM. 
This expertise has been refined within the ALTM Orion, which 
incorporates an onboard real-time waveform analyzer as part of 
its iFLEX™ technology base for rapid, precise and accurate 
XYZ data output. 
The most common type of commercial lidar sensors (Optech’s 
ALTM and Leica’s ALS series) are small-footprint discrete 
return systems that record two to four returns for each emitted 
laser pulse. Waveform sensors, which can be large- or small- 
footprint systems, digitize the full profile of a return signal in 
fixed time (i.e., distance) intervals, providing a quasi- 
continuous distribution of the reflected energy for each emitted 
laser pulse. Some lidar system manufacturers (Optech 
Incorporated) offer airborne sensors capable of both operational 
modes, where conventional discrete-return operation is 
provided by the main sensor, while full waveform data 
collection is supported by an optional unit, which may or may 
not be used during data collection missions (Optech, 2010). 
Each data collection mode, whether full waveform or discrete 
return, has distinct advantages and disadvantages that determine 
the potential applications. Most conventional discrete return 
systems can provide extremely high ground point density, This 
enables the high-resolution representation of complex targets in 
the horizontal plane with a somewhat coarsely resolved 
elevation structure, which makes the discrete return system a 
perfect choice for mapping. The additional information about 
3D elevation structure provided by multiple-return point clouds 
can be used for a variety of mapping applications including 
flood modeling (Bates et al., 1999), urban and vegetation 
analysis (Evans et al., 2009), and power line mapping 
(Ussyshkin and Sitar, 2009). In particular, airborne lidar with 
multiple-return capability has proved to be the most efficient 
among different remote sensing techniques to characterize both 
forest structure and ground topography (Chauve et al., 2007). 
However, the coarse vertical resolution, which is typically a 
few meters for many commercial airborne lidar systems, and a 
lack of detailed 3D spatial information, limit the user’s ability 
to apply more sophisticated analysis such as vegetation 
composition and change detection in land surface if the scale at 
which processes occur is less than a few meters (Wu et al., 
2009). 
On the other hand, commercially available full waveform 
airborne lidar systems (Riegl, Optech, 2010) capture full 
profiles of the laser backscattered energy for each emitted laser 
pulse as a function of time (distance) with a typical sampling 
rate of 1 ns, which is equivalent to a one-way distance of 30 
cm. They can provide much more detailed information about 
the vertical elevation structure, which could potentially be used