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International Archives of Photogrammetry and Remote Sensing, Vol. 32, Part 3W14, La Jolla, CA, 9-11 Nov. 1999
DESIGN, CAPABILITIES AND USES
OF LARGE-FOOTPRINT AND SMALL-FOOTPRINT LIDAR SYSTEMS
Joseph E. Means
Forest Science Department
Oregon State University
Corvallis, Oregon 97331, USA
joe.means@orst.edu
KEY WORDS: Lidar, Small-footprint, Large-footprint, Comparison, Design, Capabilities, Uses
ABSTRACT
The literature on airborne scanning lidars describes several types, two of which, small-footprint and large-footprint lidar, are used
in terrestrial applications. They have evolved from similar roots for different purposes. This paper summarizes their purposes,
design, functioning, capabilities and current and potential uses. Small-footprint lidars have footprints 10-90cm in diameter and
record 1-5 reflection peaks from each pulse of light. Large-footprint lidars have footprints 10-25m in diameter and record a full
digitized reflected waveform from each pulse. Data from small-footprint lidars are readily used to create high resolution, 1x1m
to 3x3m, DTMs (digital terrain models) and characterize vegetation canopy of relatively small areas. Data from large-footprint
lidars, generally at a coarser resolution, can be used to characterize topography of mineral surfaces or ice, and vertical vegetation
canopy structure of larger areas, including those with relatively dense foliage. Small-footprint lidars are commonly used for
surveying electric transmission lines, creating DTMs for right-of-ways for roads, pipelines, other transportation corridors,
forested areas, landscape planning, areas with difficult access and hazards (especially floods) assessment and mitigation planning,
and recently, 3-D modeling of urban and suburban landscapes and forest stand characterization. Large-footprint lidars are used
for measuring topography and creating DTMs over relatively large areas and characterizing
forest stand structure over large areas
including those with very dense canopies.
1 INTRODUCTION recently in the ISPRS Journal of Photogrammetry and Remote
Sensing (ISPRS, 1999). Baltsavias (1999), Wehr and Lohr
Terrestrial uses of lidar are increasing and have the potential (1999) and other papers in this issue do a great service in
to expand much farther. This potential was recognized in the documenting the current state of small-footprint lidar
published literature about 20 years ago when LIDAR was technology and the reader is referred there for further
used to map forests in Central America (Arp et al., 1982).
information on those lidars. Recent, current and future large-
The Canadian Forestry Service also recognized this in the
footprint lidars designed for terrestrial use are described by
early 1980s and conducted extensive studies of a laser (Blair et al., 1994; Blair et al., 1999: Harding et al., 1999),
altimeter profiler to characterize height and canopy closure of and on the web site
of the Vegetation Canopy Lidar
forest stands (Aldred & Bonnor, 1985).
(Dubayah et al., 1999) which is planned for launch in 2000.
Other large-footprint lidars used for surveying ice sheets and
Airborne scanning lidars all share a laser rangefinder, inertial — glaciers are described on the World Wide Web (GLAS Team,
navigation system and global positioning system mounted in a 1999; Krabill et al., 1999a; SOAR Staff, 1999). The Shuttle
fixed wing airplane or a helicopter. The laser rangefinder Laser Altimeter, last flown in 1997 (Garvin et al., 1998), and
scans the land below the advancing plane. Return times, and lidars used for bathymetric (Irish & Lillycrop, 1999),
orientations of reflections are recorded and calculated so that atmospheric (Matrosov et al., 1998), and extraterrestrial
footprint locations can be calculated with high accuracies in (Kreslavsky & Head, 1999) purposes are not discussed here.
horizontal and vertical directions. Large-footprint and small-footprint lidar systems have
different purposes, which lead to different designs,
This paper considers airborne scanning lidar (ALS) systems capabilities and uses. The remainder of this paper explores
currently or soon to be used in terrestrial applications. These these features.
systems have been described in several papers, including most
